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Szilágyi SS, Burdzinski W, Jatzlau J, Ehrlich M, Knaus P, Henis YI. The Activation of the Fibrodysplasia Ossificans Progressiva-Inducing ALK2-R206H Mutant Depends on the Distinct Homo-Oligomerization Patterns of ACVR2B and ACVR2A. Cells 2024; 13:221. [PMID: 38334613 PMCID: PMC10854824 DOI: 10.3390/cells13030221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 01/18/2024] [Accepted: 01/23/2024] [Indexed: 02/10/2024] Open
Abstract
Mutations in activin-like kinase 2 (ALK2), e.g., ALK2-R206H, induce aberrant signaling to SMAD1/5/8, leading to Fibrodysplasia Ossificans Progressiva (FOP). In spite of extensive studies, the underlying mechanism is still unclear. Here, we quantified the homomeric and heteromeric interactions of ACVR2A, ACVR2B, ALK2-WT, and ALK2-R206H by combining IgG-mediated immobilization of one receptor with fluorescence recovery after photobleaching (FRAP) measurements on the lateral diffusion of a co-expressed receptor. ACVR2B formed stable homomeric complexes that were enhanced by Activin A (ActA), while ACVR2A required ActA for homodimerization. ALK2-WT, but not ALK2-R206H, exhibited homomeric complexes unaffected by ActA. ACVR2B formed ActA-enhanced heterocomplexes with ALK2-R206H or ALK2-WT, while ACVR2A interacted mainly with ALK2-WT. The extent of the homomeric complex formation of ACVR2A or ACVR2B was reflected in their ability to induce the oligomerization of ALK2-R206H and ALK2-WT. Thus, ACVR2B, which forms dimers without ligand, induced ActA-independent ALK2-R206H clustering but required ActA for enhancing the oligomerization of the largely dimeric ALK2-WT. In contrast, ACVR2A, which undergoes homodimerization in response to ActA, required ActA to induce ALK2-R206H oligomerization. To investigate whether these interactions are translated into signaling, we studied signaling by the FOP-inducing hyperactive ALK2-R206H mutant, with ALK2-WT signaling as control. The activation of SMAD1/5/8 signaling in cells expressing ALK2-R206H alone or together with ACVR2A or ACVR2B was measured by blotting for pSMAD1/5/8 and by transcriptional activation assays using BRE-Luc reporter. In line with the biophysical studies, ACVR2B activated ALK2-R206H without ligand, while activation by ACVR2A was weaker and required ActA. We propose that the homodimerization of ACVR2B or ACVR2A dictates their ability to recruit ALK2-R206H into higher complexes, enabling the homomeric interactions of ALK2-R206H receptors and, subsequently, their activation.
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Affiliation(s)
- Szabina Szófia Szilágyi
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel;
| | - Wiktor Burdzinski
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany (J.J.); (P.K.)
- Berlin-Brandenburg School for Regenerative Therapies (BSRT), Charité-Universitätsmedizin Berlin, 13353 Berlin, Germany
| | - Jerome Jatzlau
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany (J.J.); (P.K.)
| | - Marcelo Ehrlich
- Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel;
| | - Petra Knaus
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany (J.J.); (P.K.)
| | - Yoav I. Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel;
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Sharma S, Ehrlich M, Zhang M, Blobe GC, Henis YI. NRP1 interacts with endoglin and VEGFR2 to modulate VEGF signaling and endothelial cell sprouting. Commun Biol 2024; 7:112. [PMID: 38242992 PMCID: PMC10799020 DOI: 10.1038/s42003-024-05798-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 01/09/2024] [Indexed: 01/21/2024] Open
Abstract
Endothelial cells express neuropilin 1 (NRP1), endoglin (ENG) and vascular endothelial growth factor receptor 2 (VEGFR2), which regulate VEGF-A-mediated vascular development and angiogenesis. However, the link between complex formation among these receptors with VEGF-A-induced signaling and biology is yet unclear. Here, we quantify surface receptor interactions by IgG-mediated immobilization of one receptor, and fluorescence recovery after photobleaching (FRAP) measurements of the mobility of another coexpressed receptor. We observe stable ENG/NRP1, ENG/VEGFR2, and NRP1/VEGFR2 complexes, which are enhanced by VEGF-A. ENG augments NRP1/VEGFR2 interactions, suggesting formation of tripartite complexes bridged by ENG. Effects on signaling are measured in murine embryonic endothelial cells expressing (MEEC+/+) or lacking (MEEC-/-) ENG, along with NRP1 and/or ENG overexpression or knockdown. We find that optimal VEGF-A-mediated phosphorylation of VEGFR2 and Erk1/2 requires ENG and NRP1. ENG or NRP1 increase VEGF-A-induced sprouting, becoming optimal in cells expressing all three receptors, and both processes are inhibited by a MEK1/2 inhibitor. We propose a model where the maximal potency of VEGF-A involves a tripartite complex where ENG bridges VEGFR2 and NRP1, providing an attractive therapeutic target for modulation of VEGF-A signaling and biological responses.
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Affiliation(s)
- Swati Sharma
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Marcelo Ehrlich
- Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Manqi Zhang
- Department of Medicine, Duke University Medical Center, Durham, NC, 27708, USA
| | - Gerard C Blobe
- Department of Medicine, Duke University Medical Center, Durham, NC, 27708, USA
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27708, USA
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel.
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Chaudhary R, Goodman LS, Wang S, Asimakopoulos A, Weiskirchen R, Dooley S, Ehrlich M, Henis YI. Cholesterol modulates type I/II TGF-β receptor complexes and alters the balance between Smad and Akt signaling in hepatocytes. Commun Biol 2024; 7:8. [PMID: 38168942 PMCID: PMC10761706 DOI: 10.1038/s42003-023-05654-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 11/30/2023] [Indexed: 01/05/2024] Open
Abstract
Cholesterol mediates membrane compartmentalization, affecting signaling via differential distribution of receptors and signaling mediators. While excessive cholesterol and aberrant transforming growth factor-β (TGF-β) signaling characterize multiple liver diseases, their linkage to canonical vs. non-canonical TGF-β signaling remained unclear. Here, we subjected murine hepatocytes to cholesterol depletion (CD) or enrichment (CE), followed by biophysical studies on TGF-β receptor heterocomplex formation, and output to Smad2/3 vs. Akt pathways. Prior to ligand addition, raft-dependent preformed heteromeric receptor complexes were observed. Smad2/3 phosphorylation persisted following CD or CE. CD enhanced phospho-Akt (pAkt) formation by TGF-β or epidermal growth factor (EGF) at 5 min, while reducing it at later time points. Conversely, pAkt formation by TGF-β or EGF was inhibited by CE, suggesting a direct effect on the Akt pathway. The modulation of the balance between TGF-β signaling to Smad2/3 vs. pAkt (by TGF-β or EGF) has potential implications for hepatic diseases and malignancies.
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Affiliation(s)
- Roohi Chaudhary
- Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Laureen S Goodman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Sai Wang
- Department of Medicine II, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, D-68167, Mannheim, Germany
| | - Anastasia Asimakopoulos
- Institute of Molecular Pathobiochemistry, Experimental Gene Therapy and Clinical Chemistry (IFMPEGKC), RWTH Aachen University Hospital, D-52074, Aachen, Germany
| | - Ralf Weiskirchen
- Institute of Molecular Pathobiochemistry, Experimental Gene Therapy and Clinical Chemistry (IFMPEGKC), RWTH Aachen University Hospital, D-52074, Aachen, Germany
| | - Steven Dooley
- Department of Medicine II, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, D-68167, Mannheim, Germany
| | - Marcelo Ehrlich
- Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
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Wang S, Link F, Han M, Chaudhary R, Asimakopoulos A, Liebe R, Yao Y, Hammad S, Dropmann A, Krizanac M, Rubie C, Feiner LK, Glanemann M, Ebert MPA, Weiskirchen R, Henis YI, Ehrlich M, Dooley S. The Interplay of TGF-β1 and Cholesterol Orchestrating Hepatocyte Cell Fate, EMT, and Signals for HSC Activation. Cell Mol Gastroenterol Hepatol 2023; 17:567-587. [PMID: 38154598 PMCID: PMC10883985 DOI: 10.1016/j.jcmgh.2023.12.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 12/21/2023] [Accepted: 12/22/2023] [Indexed: 12/30/2023]
Abstract
BACKGROUND & AIMS Transforming growth factor-β1 (TGF-β1) plays important roles in chronic liver diseases, including metabolic dysfunction-associated steatotic liver disease (MASLD). MASLD involves various biological processes including dysfunctional cholesterol metabolism and contributes to progression to metabolic dysfunction-associated steatohepatitis and hepatocellular carcinoma. However, the reciprocal regulation of TGF-β1 signaling and cholesterol metabolism in MASLD is yet unknown. METHODS Changes in transcription of genes associated with cholesterol metabolism were assessed by RNA sequencing of murine hepatocyte cell line (alpha mouse liver 12/AML12) and mouse primary hepatocytes treated with TGF-β1. Functional assays were performed on AML12 cells (untreated, TGF-β1 treated, or subjected to cholesterol enrichment [CE] or cholesterol depletion [CD]), and on mice injected with adenovirus-associated virus 8-control/TGF-β1. RESULTS TGF-β1 inhibited messenger RNA expression of several cholesterol metabolism regulatory genes, including rate-limiting enzymes of cholesterol biosynthesis in AML12 cells, mouse primary hepatocytes, and adenovirus-associated virus-TGF-β1-treated mice. Total cholesterol levels and lipid droplet accumulation in AML12 cells and liver tissue also were reduced upon TGF-β1 treatment. Smad2/3 phosphorylation after 2 hours of TGF-β1 treatment persisted after CE or CD and was mildly increased after CD, whereas TGF-β1-mediated AKT phosphorylation (30 min) was inhibited by CE. Furthermore, CE protected AML12 cells from several effects mediated by 72 hours of incubation with TGF-β1, including epithelial-mesenchymal transition, actin polymerization, and apoptosis. CD mimicked the outcome of long-term TGF-β1 administration, an effect that was blocked by an inhibitor of the type I TGF-β receptor. In addition, the supernatant of CE- or CD-treated AML12 cells inhibited or promoted, respectively, the activation of LX-2 hepatic stellate cells. CONCLUSIONS TGF-β1 inhibits cholesterol metabolism whereas cholesterol attenuates TGF-β1 downstream effects in hepatocytes.
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Affiliation(s)
- Sai Wang
- Department of Medicine II, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Frederik Link
- Department of Medicine II, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Mei Han
- Department of Medicine II, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany; Department of Internal Medicine, The Second Hospital of Dalian Medical University, Dalian, China
| | - Roohi Chaudhary
- Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel; Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Anastasia Asimakopoulos
- Institute of Molecular Pathobiochemistry, Experimental Gene Therapy and Clinical Chemistry, RWTH Aachen University Hospital, Aachen, Germany
| | - Roman Liebe
- Clinic of Gastroenterology, Hepatology and Infectious Diseases, Otto-von-Guericke-University, Magdeburg, Germany
| | - Ye Yao
- Department of Medicine II, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Seddik Hammad
- Department of Medicine II, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Anne Dropmann
- Department of Medicine II, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Marinela Krizanac
- Institute of Molecular Pathobiochemistry, Experimental Gene Therapy and Clinical Chemistry, RWTH Aachen University Hospital, Aachen, Germany
| | - Claudia Rubie
- Department of General, Visceral, Vascular and Pediatric Surgery, Saarland University, Homburg/Saar, Germany
| | - Laura Kim Feiner
- Department of General, Visceral, Vascular and Pediatric Surgery, Saarland University, Homburg/Saar, Germany
| | - Matthias Glanemann
- Department of General, Visceral, Vascular and Pediatric Surgery, Saarland University, Homburg/Saar, Germany
| | - Matthias P A Ebert
- Department of Medicine II, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany; Mannheim Institute for Innate Immunoscience, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany; Clinical Cooperation Unit Healthy Metabolism, Center of Preventive Medicine and Digital Health, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Ralf Weiskirchen
- Institute of Molecular Pathobiochemistry, Experimental Gene Therapy and Clinical Chemistry, RWTH Aachen University Hospital, Aachen, Germany
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Marcelo Ehrlich
- Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Steven Dooley
- Department of Medicine II, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
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Horst B, Pradhan S, Chaudhary R, Listik E, Quintero-Macias L, Choi AS, Southard M, Liu Y, Whitaker R, Hempel N, Berchuck A, Nixon AB, Lee NY, Henis YI, Mythreye K. Hypoxia-induced inhibin promotes tumor growth and vascular permeability in ovarian cancers. Commun Biol 2022; 5:536. [PMID: 35654828 PMCID: PMC9163327 DOI: 10.1038/s42003-022-03495-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 05/17/2022] [Indexed: 12/21/2022] Open
Abstract
Hypoxia, a driver of tumor growth and metastasis, regulates angiogenic pathways that are targets for vessel normalization and ovarian cancer management. However, toxicities and resistance to anti-angiogenics can limit their use making identification of new targets vital. Inhibin, a heteromeric TGFβ ligand, is a contextual regulator of tumor progression acting as an early tumor suppressor, yet also an established biomarker for ovarian cancers. Here, we find that hypoxia increases inhibin levels in ovarian cancer cell lines, xenograft tumors, and patients. Inhibin is regulated primarily through HIF-1, shifting the balance under hypoxia from activins to inhibins. Hypoxia regulated inhibin promotes tumor growth, endothelial cell invasion and permeability. Targeting inhibin in vivo through knockdown and anti-inhibin strategies robustly reduces permeability in vivo and alters the balance of pro and anti-angiogenic mechanisms resulting in vascular normalization. Mechanistically, inhibin regulates permeability by increasing VE-cadherin internalization via ACVRL1 and CD105, a receptor complex that we find to be stabilized directly by inhibin. Our findings demonstrate direct roles for inhibins in vascular normalization via TGF-β receptors providing new insights into the therapeutic significance of inhibins as a strategy to normalize the tumor vasculature in ovarian cancer. Hypoxia increases levels of the heteromeric TGFβ ligand inhibin in ovarian cancer and inhibin promotes tumor growth, endothelial cell invasion and permeability.
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Szilágyi SS, Amsalem-Zafran AR, Shapira KE, Ehrlich M, Henis YI. Competition between type I activin and BMP receptors for binding to ACVR2A regulates signaling to distinct Smad pathways. BMC Biol 2022; 20:50. [PMID: 35177083 PMCID: PMC8855587 DOI: 10.1186/s12915-022-01252-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Accepted: 02/10/2022] [Indexed: 11/17/2022] Open
Abstract
Background Activins and bone morphogenetic proteins (BMPs) play critical, sometimes opposing roles, in multiple physiological and pathological processes and diseases. They signal to distinct Smad branches; activins signal mainly to Smad2/3, while BMPs activate mainly Smad1/5/8. This gives rise to the possibility that competition between the different type I receptors through which activin and BMP signal for common type II receptors can provide a mechanism for fine-tuning the cellular response to activin/BMP stimuli. Among the transforming growth factor-β superfamily type II receptors, ACVR2A/B are highly promiscuous, due to their ability to interact with different type I receptors (e.g., ALK4 vs. ALK2/3/6) and with their respective ligands [activin A (ActA) vs. BMP9/2]. However, studies on complex formation between these full-length receptors situated at the plasma membrane, and especially on the potential competition between the different activin and BMP type I receptors for a common activin type II receptor, were lacking. Results We employed a combination of IgG-mediated patching-immobilization of several type I receptors in the absence or presence of ligands with fluorescence recovery after photobleaching (FRAP) measurements on the lateral diffusion of an activin type II receptor, ACVR2A, to demonstrate the principle of competition between type I receptors for ACVR2. Our results show that ACVR2A can form stable heteromeric complexes with ALK4 (an activin type I receptor), as well as with several BMP type I receptors (ALK2/3/6). Of note, ALK4 and the BMP type I receptors competed for binding ACVR2A. To assess the implications of this competition for signaling output, we first validated that in our cell model system (U2OS cells), ACVR2/ALK4 transduce ActA signaling to Smad2/3, while BMP9 signaling to Smad1/5/8 employ ACVR2/ALK2 or ACVR2/ALK3. By combining ligand stimulation with overexpression of a competing type I receptor, we showed that differential complex formation of distinct type I receptors with a common type II receptor balances the signaling to the two Smad branches. Conclusions Different type I receptors that signal to distinct Smad pathways (Smad2/3 vs. Smad1/5/8) compete for binding to common activin type II receptors. This provides a novel mechanism to balance signaling between Smad2/3 and Smad1/5/8. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-022-01252-z.
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Affiliation(s)
- Szabina Szófia Szilágyi
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Ayelet R Amsalem-Zafran
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Keren E Shapira
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Marcelo Ehrlich
- Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
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Abstract
Signaling by receptors from the transforming growth factor-β (TGF-β) superfamily plays critical roles in multiple physiological and pathological processes. Their signaling requires complex formation between type I and type II receptors with Ser/Thr kinase activity, whereby the type II receptor phosphorylates and activates the relevant type I receptor(s), which transduces downstream signaling. It is therefore important to study complex formation among receptors from this family. In the current chapter, we use the type I (ALK5) and type II TGF-β receptors (TβRI and TβRII) as an example for measuring complex formation among cell-surface receptors in live cells by patch-FRAP, a variation of fluorescence recovery after photobleaching (FRAP).
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Affiliation(s)
- Szabina Szófia Szilágyi
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Orit Gutman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
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Sternberg H, Buriakovsky E, Bloch D, Gutman O, Henis YI, Yalovsky S. Formation of self-organizing functionally distinct Rho of plants domains involves a reduced mobile population. Plant Physiol 2021; 187:2485-2508. [PMID: 34618086 PMCID: PMC8644358 DOI: 10.1093/plphys/kiab385] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 07/23/2021] [Indexed: 06/13/2023]
Abstract
Rho family proteins are central to the regulation of cell polarity in eukaryotes. Rho of Plants-Guanyl nucleotide Exchange Factor (ROPGEF) can form self-organizing polar domains following co-expression with an Rho of Plants (ROP) and an ROP GTPase-Activating Protein (ROPGAP). Localization of ROPs in these domains has not been demonstrated, and the mechanisms underlying domain formation and function are not well understood. Here we show that six different ROPs form self-organizing domains when co-expressed with ROPGEF3 and GAP1 in Nicotiana benthamiana or Arabidopsis (Arabidopsis thaliana). Domain formation was associated with ROP-ROPGEF3 association, reduced ROP mobility, as revealed by time-lapse imaging and Fluorescence Recovery After Photobleaching beam size analysis, and was independent of Rho GTP Dissociation Inhibitor mediated recycling. The domain formation depended on the ROPs' activation/inactivation cycles and interaction with anionic lipids via a C-terminal polybasic domain. Coexpression with the microtubule-associated protein ROP effector INTERACTOR OF CONSTITUTIVELY ACTIVE ROP 1 (ICR1) revealed differential function of the ROP domains in the ability to recruit ICR1. Taken together, the results reveal mechanisms underlying self-organizing ROP domain formation and function.
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Affiliation(s)
- Hasana Sternberg
- School of Plant Science and Food Security, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Ella Buriakovsky
- School of Plant Science and Food Security, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Daria Bloch
- School of Plant Science and Food Security, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Orit Gutman
- School of Neurobiology, Biochemistry and Biophysics, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Yoav I Henis
- School of Neurobiology, Biochemistry and Biophysics, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Shaul Yalovsky
- School of Plant Science and Food Security, Tel Aviv University, Tel Aviv 6997801, Israel
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Shapira KE, Shapira G, Schmukler E, Pasmanik-Chor M, Shomron N, Pinkas-Kramarski R, Henis YI, Ehrlich M. Autophagy is induced and modulated by cholesterol depletion through transcription of autophagy-related genes and attenuation of flux. Cell Death Discov 2021; 7:320. [PMID: 34716312 PMCID: PMC8556405 DOI: 10.1038/s41420-021-00718-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 10/12/2021] [Accepted: 10/15/2021] [Indexed: 01/18/2023] Open
Abstract
Perturbations to cellular homeostasis, including reduction of the cholesterol level, induce autophagy, a self-digestion process of cellular constituents through an autophagosomal-lysosomal pathway. In accord with its function as a membrane organizer and metabolic sentinel, the cellular response to cholesterol depletion comprises multiple phenomena, including the activation of transcriptional responses, accumulation of reactive oxygen species (ROS), and activation of stress-related signaling pathways. However, the molecular mechanisms by which cholesterol depletion regulates autophagy and the putative involvement of transcriptional responses, ROS and/or stress-related signaling in autophagy regulation in this biological context are not fully understood. Here, we find that cholesterol depletion regulates autophagy at three different levels. First, employing RNA-seq, we show that cholesterol depletion increases the expression of autophagy-related genes independent of ROS or JNK activity. Second, analysis of LC3 lipidation and intracellular localization, and of p62 levels and degradation kinetics, reveals that cholesterol depletion mediates autophagy induction while interfering with autophagic flux. Of note, only the latter depends on ROS accumulation and JNK activity. In view of the common use of cholesterol-reducing drugs as therapeutic agents, our findings have important implications for multiple cellular settings in which autophagy plays a prominent role.
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Affiliation(s)
- Keren E Shapira
- School of Neurobiology, Biochemistry and Biophysics, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Guy Shapira
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 6997801, Israel
- Edmond J Safra Center for Bioinformatics, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Eran Schmukler
- School of Neurobiology, Biochemistry and Biophysics, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Metsada Pasmanik-Chor
- Bioinformatics Unit, George S. Wise Faculty of Life Science, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Noam Shomron
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 6997801, Israel
- Edmond J Safra Center for Bioinformatics, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Ronit Pinkas-Kramarski
- School of Neurobiology, Biochemistry and Biophysics, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Yoav I Henis
- School of Neurobiology, Biochemistry and Biophysics, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel.
| | - Marcelo Ehrlich
- Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel.
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Tazat K, Pomeraniec-Abudy L, Hector-Greene M, Szilágyi SS, Sharma S, Cai EM, Corona AL, Ehrlich M, Blobe GC, Henis YI. ALK1 regulates the internalization of endoglin and the type III TGF-β receptor. Mol Biol Cell 2021; 32:605-621. [PMID: 33566682 PMCID: PMC8101464 DOI: 10.1091/mbc.e20-03-0199] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Complex formation and endocytosis of transforming growth factor-β (TGF-β) receptors play important roles in signaling. However, their interdependence remained unexplored. Here, we demonstrate that ALK1, a TGF-β type I receptor prevalent in endothelial cells, forms stable complexes at the cell surface with endoglin and with type III TGF-β receptors (TβRIII). We show that ALK1 undergoes clathrin-mediated endocytosis (CME) faster than ALK5, type II TGF-β receptor (TβRII), endoglin, or TβRIII. These complexes regulate the endocytosis of the TGF-β receptors, with a major effect mediated by ALK1. Thus, ALK1 enhances the endocytosis of TβRIII and endoglin, while ALK5 and TβRII mildly enhance endoglin, but not TβRIII, internalization. Conversely, the slowly endocytosed endoglin has no effect on the endocytosis of either ALK1, ALK5, or TβRII, while TβRIII has a differential effect, slowing the internalization of ALK5 and TβRII, but not ALK1. Such effects may be relevant to signaling, as BMP9-mediated Smad1/5/8 phosphorylation is inhibited by CME blockade in endothelial cells. We propose a model that links TGF-β receptor oligomerization and endocytosis, based on which endocytosis signals are exposed/functional in specific receptor complexes. This has broad implications for signaling, implying that complex formation among various receptors regulates their surface levels and signaling intensities.
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Affiliation(s)
- Keren Tazat
- Department of Neurobiology, Tel Aviv University, Tel Aviv 6997801, Israel
| | | | | | | | - Swati Sharma
- Department of Neurobiology, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Elise M Cai
- Department of Medicine, Duke University Medical Center, Durham, NC 27708
| | - Armando L Corona
- Department of Medicine, Duke University Medical Center, Durham, NC 27708
| | - Marcelo Ehrlich
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Gerard C Blobe
- Department of Medicine, Duke University Medical Center, Durham, NC 27708
| | - Yoav I Henis
- Department of Neurobiology, Tel Aviv University, Tel Aviv 6997801, Israel
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11
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Menuchin-Lasowski Y, Dagan B, Conidi A, Cohen-Gulkar M, David A, Ehrlich M, Giladi PO, Clark BS, Blackshaw S, Shapira K, Huylebroeck D, Henis YI, Ashery-Padan R. Zeb2 regulates the balance between retinal interneurons and Müller glia by inhibition of BMP-Smad signaling. Dev Biol 2020; 468:80-92. [PMID: 32950463 DOI: 10.1016/j.ydbio.2020.09.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 08/24/2020] [Accepted: 09/10/2020] [Indexed: 12/27/2022]
Abstract
The interplay between signaling molecules and transcription factors during retinal development is key to controlling the correct number of retinal cell types. Zeb2 (Sip1) is a zinc-finger multidomain transcription factor that plays multiple roles in central and peripheral nervous system development. Haploinsufficiency of ZEB2 causes Mowat-Wilson syndrome, a congenital disease characterized by intellectual disability, epilepsy and Hirschsprung disease. In the developing retina, Zeb2 is required for generation of horizontal cells and the correct number of interneurons; however, its potential function in controlling gliogenic versus neurogenic decisions remains unresolved. Here we present cellular and molecular evidence of the inhibition of Müller glia cell fate by Zeb2 in late stages of retinogenesis. Unbiased transcriptomic profiling of control and Zeb2-deficient early-postnatal retina revealed that Zeb2 functions in inhibiting Id1/2/4 and Hes1 gene expression. These neural progenitor factors normally inhibit neural differentiation and promote Müller glia cell fate. Chromatin immunoprecipitation (ChIP) supported direct regulation of Id1 by Zeb2 in the postnatal retina. Reporter assays and ChIP analyses in differentiating neural progenitors provided further evidence that Zeb2 inhibits Id1 through inhibition of Smad-mediated activation of Id1 transcription. Together, the results suggest that Zeb2 promotes the timely differentiation of retinal interneurons at least in part by repressing BMP-Smad/Notch target genes that inhibit neurogenesis. These findings show that Zeb2 integrates extrinsic cues to regulate the balance between neuronal and glial cell types in the developing murine retina.
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Affiliation(s)
- Yotam Menuchin-Lasowski
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Bar Dagan
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Andrea Conidi
- Department of Cell Biology, Erasmus University Medical Center, Rotterdam 3015 CN, the Netherlands
| | - Mazal Cohen-Gulkar
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ahuvit David
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Marcelo Ehrlich
- Shumins School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Pazit Oren Giladi
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Brian S Clark
- John F Hardesty, MD Department of Ophthalmology and Visual Sciences and Department of Developmental Biology, Washington University, St. Louis, MO 63110, USA
| | - Seth Blackshaw
- Solomon H. Snyder Department of Neuroscience, Baltimore, MD 21205, USA; Department of Ophthalmology, Baltimore, MD 21205, USA; Department of Neurology, Baltimore, MD 21205, USA; Center for Human Systems Biology, Baltimore, MD 21205, USA; Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Keren Shapira
- Shumins School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | - Danny Huylebroeck
- Department of Cell Biology, Erasmus University Medical Center, Rotterdam 3015 CN, the Netherlands; Department of Development and Regeneration, KU Leuven, Leuven 3000, Belgium
| | - Yoav I Henis
- Shumins School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ruth Ashery-Padan
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel.
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12
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Wist M, Meier L, Gutman O, Haas J, Endres S, Zhou Y, Rösler R, Wiese S, Stilgenbauer S, Hobeika E, Henis YI, Gierschik P, Walliser C. Noncatalytic Bruton's tyrosine kinase activates PLCγ 2 variants mediating ibrutinib resistance in human chronic lymphocytic leukemia cells. J Biol Chem 2020; 295:5717-5736. [PMID: 32184360 DOI: 10.1074/jbc.ra119.011946] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 02/26/2020] [Indexed: 12/25/2022] Open
Abstract
Treatment of patients with chronic lymphocytic leukemia (CLL) with inhibitors of Bruton's tyrosine kinase (BTK), such as ibrutinib, is limited by primary or secondary resistance to this drug. Examinations of CLL patients with late relapses while on ibrutinib, which inhibits BTK's catalytic activity, revealed several mutations in BTK, most frequently resulting in the C481S substitution, and disclosed many mutations in PLCG2, encoding phospholipase C-γ2 (PLCγ2). The PLCγ2 variants typically do not exhibit constitutive activity in cell-free systems, leading to the suggestion that in intact cells they are hypersensitive to Rac family small GTPases or to the upstream kinases spleen-associated tyrosine kinase (SYK) and Lck/Yes-related novel tyrosine kinase (LYN). The sensitivity of the PLCγ2 variants to BTK itself has remained unknown. Here, using genetically-modified DT40 B lymphocytes, along with various biochemical assays, including analysis of PLCγ2-mediated inositol phosphate formation, inositol phospholipid assessments, fluorescence recovery after photobleaching (FRAP) static laser microscopy, and determination of intracellular calcium ([Ca2+] i ), we show that various CLL-specific PLCγ2 variants such as PLCγ2S707Y are hyper-responsive to activated BTK, even in the absence of BTK's catalytic activity and independently of enhanced PLCγ2 phospholipid substrate supply. At high levels of B-cell receptor (BCR) activation, which may occur in individual CLL patients, catalytically-inactive BTK restored the ability of the BCR to mediate increases in [Ca2+] i Because catalytically-inactive BTK is insensitive to active-site BTK inhibitors, the mechanism involving the noncatalytic BTK uncovered here may contribute to preexisting reduced sensitivity or even primary resistance of CLL to these drugs.
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Affiliation(s)
- Martin Wist
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Laura Meier
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Orit Gutman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Jennifer Haas
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Sascha Endres
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Yuan Zhou
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Reinhild Rösler
- Core Unit Mass Spectrometry and Proteomics, Medical Faculty, Ulm University Medical Center, 89081 Ulm, Germany
| | - Sebastian Wiese
- Core Unit Mass Spectrometry and Proteomics, Medical Faculty, Ulm University Medical Center, 89081 Ulm, Germany
| | - Stephan Stilgenbauer
- Department of Internal Medicine III, Ulm University Medical Center, 89081 Ulm, Germany
| | - Elias Hobeika
- Institute of Immunology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Peter Gierschik
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany.
| | - Claudia Walliser
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany.
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13
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Shapira KE, Ehrlich M, Henis YI. Cholesterol depletion enhances TGF-β Smad signaling by increasing c-Jun expression through a PKR-dependent mechanism. Mol Biol Cell 2018; 29:2494-2507. [PMID: 30091670 PMCID: PMC6233055 DOI: 10.1091/mbc.e18-03-0175] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 07/16/2018] [Accepted: 07/25/2018] [Indexed: 02/06/2023] Open
Abstract
Transforming growth factor-β (TGF-β) plays critical roles in numerous physiological and pathological responses. Cholesterol, a major plasma membrane component, can have pronounced effects on signaling responses. Cells continually monitor cholesterol content and activate multilayered transcriptional and translational signaling programs, following perturbations to cholesterol homeostasis (e.g., statins, the commonly used cholesterol-reducing drugs). However, the cross-talk of such programs with ligand-induced signaling responses (e.g., TGF-β signaling) remained unknown. Here, we studied the effects of a mild reduction in free (membrane-associated) cholesterol on distinct components of TGF-β-signaling pathways. Our findings reveal a new regulatory mechanism that enhances TGF-β-signaling responses by acting downstream from receptor activation. Reduced cholesterol results in PKR-dependent eIF2α phosphorylation, which enhances c-Jun translation, leading in turn to higher levels of JNK-mediated c-Jun phosphorylation. Activated c-Jun enhances transcription and expression of Smad2/3. This leads to enhanced sensitivity to TGF-β stimulation, due to increased Smad2/3 expression and phosphorylation. The phospho/total Smad2/3 ratio remains unchanged, indicating that the effect is not due to altered receptor activity. We propose that cholesterol depletion induces overactivation of PKR, JNK, and TGF-β signaling, which together may contribute to the side effects of statins in diverse disease settings.
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Affiliation(s)
- Keren E. Shapira
- Department of Neurobiology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Marcelo Ehrlich
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Yoav I. Henis
- Department of Neurobiology, Tel Aviv University, Tel Aviv 69978, Israel
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14
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Varadaraj A, Jenkins LM, Singh P, Chanda A, Snider J, Lee NY, Amsalem-Zafran AR, Ehrlich M, Henis YI, Mythreye K. TGF-β triggers rapid fibrillogenesis via a novel TβRII-dependent fibronectin-trafficking mechanism. Mol Biol Cell 2017; 28:1195-1207. [PMID: 28298487 PMCID: PMC5415016 DOI: 10.1091/mbc.e16-08-0601] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 02/22/2017] [Accepted: 02/27/2017] [Indexed: 02/02/2023] Open
Abstract
There is increased recycling of soluble fibronectin from the cell surface for fibrillogenesis. This recycling is regulated by TGF-β in a transcription- and SMAD-independent manner via specific TβRII and integrin α5β1 interactions. The recycling of fibronectin is Rab11 dependent and is required for TGF-β–induced cell migration. Fibronectin (FN) is a critical regulator of extracellular matrix (ECM) remodeling through its availability and stepwise polymerization for fibrillogenesis. Availability of FN is regulated by its synthesis and turnover, and fibrillogenesis is a multistep, integrin-dependent process essential for cell migration, proliferation, and tissue function. Transforming growth factor β (TGF-β) is an established regulator of ECM remodeling via transcriptional control of ECM proteins. Here we show that TGF-β, through increased FN trafficking in a transcription- and SMAD-independent manner, is a direct and rapid inducer of the fibrillogenesis required for TGF-β–induced cell migration. Whereas TGF-β signaling is dispensable for rapid fibrillogenesis, stable interactions between the cytoplasmic domain of the type II TGF-β receptor (TβRII) and the FN receptor (α5β1 integrin) are required. We find that, in response to TGF-β, cell surface–internalized FN is not degraded by the lysosome but instead undergoes recycling and incorporation into fibrils, a process dependent on TβRII. These findings are the first to show direct use of trafficked and recycled FN for fibrillogenesis, with a striking role for TGF-β in this process. Given the significant physiological consequences associated with FN availability and polymerization, our findings provide new insights into the regulation of fibrillogenesis for cellular homeostasis.
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Affiliation(s)
- Archana Varadaraj
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208
| | - Laura M Jenkins
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208
| | - Priyanka Singh
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208
| | - Anindya Chanda
- Department of Environmental Health Sciences, University of South Carolina, Columbia, SC 29201
| | - John Snider
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208
| | - N Y Lee
- Division of Pharmacology, College of Pharmacy, Ohio State University, Columbus, OH 43210
| | | | - Marcelo Ehrlich
- Department of Cell Research and Immunology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Yoav I Henis
- Department of Neurobiology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Karthikeyan Mythreye
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208 .,Department of Drug Discovery and Biomedical Sciences, University of South Carolina, Columbia, SC 29208
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15
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Gottlieb-Abraham E, Gutman O, Pai GM, Rubio I, Henis YI. The residue at position 5 of the N-terminal region of Src and Fyn modulates their myristoylation, palmitoylation, and membrane interactions. Mol Biol Cell 2016; 27:3926-3936. [PMID: 27733622 PMCID: PMC5170614 DOI: 10.1091/mbc.e16-08-0622] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/03/2016] [Accepted: 10/05/2016] [Indexed: 01/19/2023] Open
Abstract
Using biophysical methods in live cells and palmitoylation mutants of Src and Fyn, we show that palmitoylation stabilizes the interactions of SFKs with the plasma membrane. Moreover, we show that the amino acid at position 5 regulates the myristoylation and palmitoylation of these proteins, and thereby their targeting to raft domains. The interactions of Src family kinases (SFKs) with the plasma membrane are crucial for their activity. They depend on their fatty-acylated N-termini, containing N-myristate and either a polybasic cluster (in Src) or palmitoylation sites (e.g., Fyn). To investigate the roles of these moieties in SFK membrane association, we used fluorescence recovery after photobleaching beam-size analysis to study the membrane interactions of c-Src-GFP (green fluorescent protein) or Fyn-GFP fatty-acylation mutants. Our studies showed for the first time that the membrane association of Fyn is more stable than that of Src, an effect lost in a Fyn mutant lacking the palmitoylation sites. Unexpectedly, Src-S3C/S6C (containing cysteines at positions 3/6, which are palmitoylated in Fyn) exhibited fast cytoplasmic diffusion insensitive to palmitoylation inhibitors, suggesting defective fatty acylation. Further replacement of the charged Lys-5 by neutral Gln to resemble Fyn (Src-S3C/S6C/K5Q) restored Fyn-like membrane interactions, indicating that Lys-5 in the context of Src-S3C/S6C interferes with its myristoylation/palmitoylation. This was validated by direct myristoylation and palmitoylation studies, which indicated that the residue at position 5 regulates the membrane interactions of Src versus Fyn. Moreover, the palmitoylation levels correlated with targeting to detergent-resistant membranes (rafts) and to caveolin-1. Palmitoylation-dependent preferential containment of Fyn in rafts may contribute to its lower transformation potential.
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Affiliation(s)
- Efrat Gottlieb-Abraham
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Orit Gutman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Govind M Pai
- Institute of Molecular Cell Biology, Center for Molecular Biomedicine, University Hospital, Jena 07745, Germany
| | - Ignacio Rubio
- Institute of Molecular Cell Biology, Center for Molecular Biomedicine, University Hospital, Jena 07745, Germany
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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16
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Paarmann P, Dörpholz G, Fiebig J, Amsalem AR, Ehrlich M, Henis YI, Müller T, Knaus P. Dynamin-dependent endocytosis of Bone Morphogenetic Protein2 (BMP2) and its receptors is dispensable for the initiation of Smad signaling. Int J Biochem Cell Biol 2016; 76:51-63. [PMID: 27113717 DOI: 10.1016/j.biocel.2016.04.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 03/18/2016] [Accepted: 04/21/2016] [Indexed: 01/07/2023]
Abstract
Bone Morphogenetic Protein (BMP) signal transduction via the canonical Smad158 pathway has previously been linked to dynamin-dependent endocytosis, since the application of chemical inhibitors of clathrin or dynamin in functional cell culture based assays negatively affects initiation and propagation of the Smad response. More recent studies, however, demonstrated efficient Smad signaling by non-internalizable BMP2. The role of endocytosis in BMP signal transduction thus remained controversial. In our study we aimed to refine cell biological assays and to apply novel tools, including a new site-directed fluorescently labeled BMP2 ligand, to revisit key steps in BMP Smad signaling. We found that dynamin2 function was required for BMP2 uptake but was dispensable for C-terminal phosphorylation, nuclear translocation and transcriptional activity of BMP-dependent Smads. Furthermore, we demonstrated a role of dynamin2 in the regulation of steady-state and surface BMP receptor levels, as well as an impact on Smad1 protein level. Thus, dynamin2 allows for modulation of basal and ligand-dependent Smad signaling capacity. High levels of functional dynamin2 enhanced the myogenic differentiation of precursor cells. From our study we conclude that dynamin-dependent endocytosis serves as a regulatory mechanism to fine-tune Smad signaling, but it is not a prerequisite for signal initiation and propagation. Our findings contribute to the understanding of fundamental mechanisms of BMP signaling and thus provide important information for future consideration in the context of therapeutic applications of BMPs.
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Affiliation(s)
- Pia Paarmann
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany
| | - Gina Dörpholz
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany
| | - Juliane Fiebig
- Department for Molecular Plant Physiology and Biophysics, Biozentrum Universität Würzburg, Julius-von-Sachs Institute, Julius-von-Sachs Platz 2, 97082 Würzburg, Germany
| | - Ayelet R Amsalem
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Marcelo Ehrlich
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Thomas Müller
- Department for Molecular Plant Physiology and Biophysics, Biozentrum Universität Würzburg, Julius-von-Sachs Institute, Julius-von-Sachs Platz 2, 97082 Würzburg, Germany
| | - Petra Knaus
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany.
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17
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Amsalem AR, Marom B, Shapira KE, Hirschhorn T, Preisler L, Paarmann P, Knaus P, Henis YI, Ehrlich M. Differential regulation of translation and endocytosis of alternatively spliced forms of the type II bone morphogenetic protein (BMP) receptor. Mol Biol Cell 2016; 27:716-30. [PMID: 26739752 PMCID: PMC4750929 DOI: 10.1091/mbc.e15-08-0547] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 12/24/2015] [Indexed: 12/22/2022] Open
Abstract
The cytoplasmic extension of the long-form isoform of BMPRII, unique among TGF-β superfamily receptors, is found to regulate the translation of BMPRII and its clathrin-mediated endocytosis. Both processes reduce its cell surface levels. The higher expression of BMPRII-SF at the plasma membrane results in enhanced activation of Smad signaling. The expression and function of transforming growth factor-β superfamily receptors are regulated by multiple molecular mechanisms. The type II BMP receptor (BMPRII) is expressed as two alternatively spliced forms, a long and a short form (BMPRII-LF and –SF, respectively), which differ by an ∼500 amino acid C-terminal extension, unique among TGF-β superfamily receptors. Whereas this extension was proposed to modulate BMPRII signaling output, its contribution to the regulation of receptor expression was not addressed. To map regulatory determinants of BMPRII expression, we compared synthesis, degradation, distribution, and endocytic trafficking of BMPRII isoforms and mutants. We identified translational regulation of BMPRII expression and the contribution of a 3’ terminal coding sequence to this process. BMPRII-LF and -SF differed also in their steady-state levels, kinetics of degradation, intracellular distribution, and internalization rates. A single dileucine signal in the C-terminal extension of BMPRII-LF accounted for its faster clathrin-mediated endocytosis relative to BMPRII-SF, accompanied by mildly faster degradation. Higher expression of BMPRII-SF at the plasma membrane resulted in enhanced activation of Smad signaling, stressing the potential importance of the multilayered regulation of BMPRII expression at the plasma membrane.
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Affiliation(s)
- Ayelet R Amsalem
- Department of Neurobiology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Barak Marom
- Department of Neurobiology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Keren E Shapira
- Department of Neurobiology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Tal Hirschhorn
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Livia Preisler
- Department of Neurobiology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Pia Paarmann
- Institute for Chemistry and Biochemistry, Freie Univesitaet Berlin, 1495 Berlin, Germany
| | - Petra Knaus
- Institute for Chemistry and Biochemistry, Freie Univesitaet Berlin, 1495 Berlin, Germany
| | - Yoav I Henis
- Department of Neurobiology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Marcelo Ehrlich
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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18
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Sorek N, Segev O, Gutman O, Bar E, Richter S, Poraty L, Hirsch JA, Henis YI, Lewinsohn E, Jürgens G, Yalovsky S. An S-Acylation Switch of Conserved G Domain Cysteines Is Required for Polarity Signaling by ROP GTPases. Curr Biol 2015; 25:2875-2877. [DOI: 10.1016/j.cub.2015.10.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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19
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Tazat K, Hector-Greene M, Blobe GC, Henis YI. TβRIII independently binds type I and type II TGF-β receptors to inhibit TGF-β signaling. Mol Biol Cell 2015; 26:3535-45. [PMID: 26269580 PMCID: PMC4591696 DOI: 10.1091/mbc.e15-04-0203] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 08/05/2015] [Indexed: 02/01/2023] Open
Abstract
Study of the TβRIII interaction with the signaling TGF-β receptors shows that TβRIII homo-oligomerization is indirect, depending largely on interactions with GIPC scaffolds. TβRI and II bind independently to TβRIII, competing with TβRI-TβRII complex formation and inhibiting Smad2/3 signaling by a mechanism independent of TβRIII ectodomain shedding. Transforming growth factor-β (TGF-β) receptor oligomerization has important roles in signaling. Complex formation among type I and type II (TβRI and TβRII) TGF-β receptors is well characterized and is essential for signal transduction. However, studies on their interactions with the type III TGF-β coreceptor (TβRIII) in live cells and their effects on TGF-β signaling are lacking. Here we investigated the homomeric and heteromeric interactions of TβRIII with TβRI and TβRII in live cells by combining IgG-mediated patching/immobilization of a given TGF-β receptor with fluorescence recovery after photobleaching studies on the lateral diffusion of a coexpressed receptor. Our studies demonstrate that TβRIII homo-oligomerization is indirect and depends on its cytoplasmic domain interactions with scaffold proteins (mainly GIPC). We show that TβRII and TβRI bind independently to TβRIII, whereas TβRIII augments TβRI/TβRII association, suggesting that TβRI and TβRII bind to TβRIII simultaneously but not as a complex. TβRIII expression inhibited TGF-β–mediated Smad2/3 signaling in MDA-MB-231 cell lines, an effect that depended on the TβRIII cytoplasmic domain and did not require TβRIII ectodomain shedding. We propose that independent binding of TβRI and TβRII to TβRIII competes with TβRI/TβRII signaling complex formation, thus inhibiting TGF-β–mediated Smad signaling.
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Affiliation(s)
- Keren Tazat
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | | | - Gerard C Blobe
- Department of Medicine, Duke University Medical Center, Durham, NC 27708 Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27708
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel )
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20
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Pomeraniec L, Hector-Greene M, Ehrlich M, Blobe GC, Henis YI. Regulation of TGF-β receptor hetero-oligomerization and signaling by endoglin. Mol Biol Cell 2015; 26:3117-27. [PMID: 26157163 PMCID: PMC4551323 DOI: 10.1091/mbc.e15-02-0069] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 06/30/2015] [Indexed: 11/23/2022] Open
Abstract
Endoglin is a modulator of TGF-β signaling in endothelial cells. We show that it forms stable homodimers serving as a scaffold for binding TβRII, ALK5, and ALK1. ALK1 and ALK5 bind endoglin differentially, with TβRII recruiting ALK5. Signaling data indicate a role for this receptor complex in balancing TGF-β signaling between Smad1/5/8 and Smad2/3. Complex formation among transforming growth factor-β (TGF-β) receptors and its modulation by coreceptors represent an important level of regulation for TGF-β signaling. Oligomerization of ALK5 and the type II TGF-β receptor (TβRII) has been thoroughly investigated, both in vitro and in intact cells. However, such studies, especially in live cells, are missing for the endothelial cell coreceptor endoglin and for the ALK1 type I receptor, which enables endothelial cells to respond to TGF-β by activation of both Smad2/3 and Smad1/5/8. Here we combined immunoglobulin G–mediated immobilization of one cell-surface receptor with lateral mobility studies of a coexpressed receptor by fluorescence recovery after photobleaching (FRAP) to demonstrate that endoglin forms stable homodimers that function as a scaffold for binding TβRII, ALK5, and ALK1. ALK1 and ALK5 bind to endoglin with differential dependence on TβRII, which plays a major role in recruiting ALK5 to the complex. Signaling data indicate a role for the quaternary receptor complex in regulating the balance between TGF-β signaling to Smad1/5/8 and to Smad2/3.
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Affiliation(s)
- Leslie Pomeraniec
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | | | - Marcelo Ehrlich
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Gerard C Blobe
- Department of Medicine, Duke University Medical Center, Durham, NC 27708
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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21
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Walliser C, Tron K, Clauss K, Gutman O, Kobitski AY, Retlich M, Schade A, Röcker C, Henis YI, Nienhaus GU, Gierschik P. Rac-mediated Stimulation of Phospholipase Cγ2 Amplifies B Cell Receptor-induced Calcium Signaling. J Biol Chem 2015; 290:17056-72. [PMID: 25903139 DOI: 10.1074/jbc.m115.645739] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Indexed: 12/21/2022] Open
Abstract
The Rho GTPase Rac is crucially involved in controlling multiple B cell functions, including those regulated by the B cell receptor (BCR) through increased cytosolic Ca(2+). The underlying molecular mechanisms and their relevance to the functions of intact B cells have thus far remained unknown. We have previously shown that the activity of phospholipase Cγ2 (PLCγ2), a key constituent of the BCR signalosome, is stimulated by activated Rac through direct protein-protein interaction. Here, we use a Rac-resistant mutant of PLCγ2 to functionally reconstitute cultured PLCγ2-deficient DT40 B cells and to examine the effects of the Rac-PLCγ2 interaction on BCR-mediated changes of intracellular Ca(2+) and regulation of Ca(2+)-regulated and nuclear-factor-of-activated-T-cell-regulated gene transcription at the level of single, intact B cells. The results show that the functional Rac-PLCγ2 interaction causes marked increases in the following: (i) sensitivity of B cells to BCR ligation; (ii) BCR-mediated Ca(2+) release from intracellular stores; (iii) Ca(2+) entry from the extracellular compartment; and (iv) nuclear translocation of the Ca(2+)-regulated nuclear factor of activated T cells. Hence, Rac-mediated stimulation of PLCγ2 activity serves to amplify B cell receptor-induced Ca(2+) signaling.
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Affiliation(s)
- Claudia Walliser
- From the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany
| | - Kyrylo Tron
- the Institute of Biophysics, University of Ulm, 89069 Ulm, Germany
| | - Karen Clauss
- the Institute of Biophysics, University of Ulm, 89069 Ulm, Germany
| | - Orit Gutman
- the Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Andrei Yu Kobitski
- the Institute of Applied Physics and Center for Functional Nanostructures, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Michael Retlich
- From the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany
| | - Anja Schade
- From the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany
| | - Carlheinz Röcker
- the Institute of Biophysics, University of Ulm, 89069 Ulm, Germany
| | - Yoav I Henis
- the Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - G Ulrich Nienhaus
- the Institute of Applied Physics and Center for Functional Nanostructures, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany, the Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany, and the Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Peter Gierschik
- From the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany,
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Abstract
The epidermal growth factor receptor (EGFR) undergoes a conformational change in response to ligand binding. The ligand-induced changes in cell surface aggregation and mobility have a profound effect on the function of all the family members. Ligand also activates the EGFR intracellular kinase, stimulating proliferation and cell survival. The EGFR family are often activated, overexpressed or mutated in cancer cells and therapeutic drugs (including antibodies) can slow the progress of some cancers. This article provides a brief, annotated summary of the presentations and discussion which occurred at the Epidermal Growth Factor Receptor - Future Directions Conference held in Jerusalem in November 2013.
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Affiliation(s)
- Antony W Burgess
- The Walter & Eliza Hall Institute of Medical Research, Burgess Lab Structural Biology , Parkville , Australia
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23
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Abstract
TGF-β signals through Smad-dependent and non-Smad pathways, depending on cell context. In ovarian cancer cells, the clathrin adaptor Dab2 enhances internalization of the type I TGF-β receptor, restricts its lateral mobility, and inhibits TGF-β–mediated, cholesterol-dependent JNK activation. Transforming growth factor-β (TGF-β) ligands activate Smad-mediated and noncanonical signaling pathways in a cell context–dependent manner. Localization of signaling receptors to distinct membrane domains is a potential source of signaling output diversity. The tumor suppressor/endocytic adaptor protein disabled-2 (Dab2) was proposed as a modulator of TGF-β signaling. However, the molecular mechanism(s) involved in the regulation of TGF-β signaling by Dab2 were not known. Here we investigate these issues by combining biophysical studies of the lateral mobility and endocytosis of the type I TGF-β receptor (TβRI) with TGF-β phosphoprotein signaling assays. Our findings demonstrate that Dab2 interacts with TβRI to restrict its lateral diffusion at the plasma membrane and enhance its clathrin-mediated endocytosis. Small interfering RNA–mediated knockdown of Dab2 or Dab2 overexpression shows that Dab2 negatively regulates TGF-β–induced c-Jun N-terminal kinase (JNK) activation, whereas activation of the Smad pathway is unaffected. Moreover, activation of JNK by TGF-β in the absence of Dab2 is disrupted by cholesterol depletion. These data support a model in which Dab2 regulates the domain localization of TβRI in the membrane, balancing TGF-β signaling via the Smad and JNK pathways.
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Affiliation(s)
- Keren E Shapira
- Department of Neurobiology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Tal Hirschhorn
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Lior Barzilay
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Nechama I Smorodinsky
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Yoav I Henis
- Department of Neurobiology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Marcelo Ehrlich
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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Gottlieb-Abraham E, Shvartsman DE, Donaldson JC, Ehrlich M, Gutman O, Martin GS, Henis YI. Src-mediated caveolin-1 phosphorylation affects the targeting of active Src to specific membrane sites. Mol Biol Cell 2013; 24:3881-95. [PMID: 24131997 PMCID: PMC3861084 DOI: 10.1091/mbc.e13-03-0163] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 10/07/2013] [Accepted: 10/08/2013] [Indexed: 01/29/2023] Open
Abstract
Src interactions with the plasma membrane are an important determinant of its activity. In turn, Src activity modulates its association with the membrane through binding of activated Src to phosphotyrosylated proteins. Caveolin-1 (Cav-1), a major component of caveolae, is a known Src phosphorylation target, and both were reported to regulate cell transformation. However, the nature of Src-Cav-1 interactions, a potential mechanism of their coregulation, remained unclear. Here we used fluorescence recovery after photobleaching beam-size analysis, coimmunoprecipitation, quantitative imaging, and far-Western studies with cells expressing wild type, as well as structural and activity mutants of Src-green fluorescent protein and Cav-1-monomeric red fluorescent protein, to measure their interactions with the membrane and with each other. We show dynamic Src-plasma membrane interactions, which are augmented and stabilized by Cav-1. The mechanism involves phosphorylation of Cav-1 at Tyr-14 by Src and subsequent binding of the Src SH2 domain to phospho-Cav-1, leading to accumulation of activated Src in focal adhesions. This novel Cav-1 function potentially modulates focal adhesion dynamics.
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Affiliation(s)
- Efrat Gottlieb-Abraham
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Dmitry E. Shvartsman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - John C. Donaldson
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Marcelo Ehrlich
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Orit Gutman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - G. Steven Martin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Yoav I. Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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25
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Lavelin I, Wolfenson H, Patla I, Henis YI, Medalia O, Volberg T, Livne A, Kam Z, Geiger B. Differential effect of actomyosin relaxation on the dynamic properties of focal adhesion proteins. PLoS One 2013; 8:e73549. [PMID: 24039980 PMCID: PMC3767655 DOI: 10.1371/journal.pone.0073549] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 07/22/2013] [Indexed: 12/21/2022] Open
Abstract
Treatment of cultured cells with inhibitors of actomyosin contractility induces rapid deterioration of stress fibers, and disassembly of the associated focal adhesions (FAs). In this study, we show that treatment with the Rho kinase inhibitor Y-27632, which blocks actomyosin contractility, induces disarray in the FA-associated actin bundles, followed by the differential dissociation of eight FA components from the adhesion sites. Live-cell microscopy indicated that the drug triggers rapid dissociation of VASP and zyxin from FAs (τ values of 7-8 min), followed by talin, paxillin and ILK (τ ~16 min), and then by FAK, vinculin and kindlin-2 (τ = 25-28 min). Examination of the molecular kinetics of the various FA constituents, using Fluorescence Recovery After Photobleaching (FRAP), in the absence of or following short-term treatment with the drug, revealed major changes in the kon and koff values of the different proteins tested, which are in close agreement with their differential dissociation rates from the adhesion sites. These findings indicate that mechanical, actomyosin-generated forces differentially regulate the molecular kinetics of individual FA-associated molecules, and thereby modulate FA composition and stability.
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Affiliation(s)
- Irena Lavelin
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Haguy Wolfenson
- Department of Neurobiology, Tel Aviv University, Tel Aviv, Israel
| | - Israel Patla
- Department of Life Sciences and the National Institute for Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Be’er-Sheva, Israel
| | - Yoav I. Henis
- Department of Neurobiology, Tel Aviv University, Tel Aviv, Israel
| | - Ohad Medalia
- Department of Life Sciences and the National Institute for Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Be’er-Sheva, Israel
- Department of Biochemistry, University of Zurich, Zürich, Switzerland
| | - Tova Volberg
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Ariel Livne
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Zvi Kam
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Benjamin Geiger
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
- * E-mail:
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26
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Abstract
Constitutive activation or overactivation of Ras signaling pathways contributes to epithelial tumorigenesis in several ways, one of which is cytoplasmic mislocalization of the cyclin-dependent kinase inhibitor p27(Kip1) (p27). We previously showed that such an effect can be mediated by activation of the Ral-GEF pathway by oncogenic N-Ras. However, the mechanism(s) leading to p27 cytoplasmic accumulation downstream of activated Ral remained unknown. Here, we report a dual regulation of p27 cellular localization by Ral downstream pathways, based on opposing effects via the Ral effectors RalBP1 and phospholipase D1 (PLD1). Because RalA and RalB are equally effective in mislocalizing both murine and human p27, we focus on RalA and murine p27, which lacks the Thr-157 phosphorylation site of human p27. In experiments based on specific RalA and p27 mutants, complemented with short hairpin RNA-mediated knockdown of Ral downstream signaling components, we show that activation of RalBP1 induces cytoplasmic accumulation of p27 and that this event requires p27 Ser-10 phosphorylation by protein kinase B/Akt. Of note, activation of PLD1 counteracts this effect in a Ser-10-independent manner. The physiological relevance of the modulation of p27 localization by Ral is demonstrated by the ability of Ral-mediated activation of the RalBP1 pathway to abrogate transforming growth factor-β-mediated growth arrest in epithelial cells.
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Affiliation(s)
- Keren Tazat
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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27
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Henis YI, Marom B, Shapira KE, Knaus P, Ehrlich M. TGF-Beta and Bmp Receptors: Distinct Modes of Oligomeric Interactions and Implications for Signaling. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.3393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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28
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Shapira KE, Gross A, Ehrlich M, Henis YI. Coated pit-mediated endocytosis of the type I transforming growth factor-β (TGF-β) receptor depends on a di-leucine family signal and is not required for signaling. J Biol Chem 2012; 287:26876-89. [PMID: 22707720 DOI: 10.1074/jbc.m112.362848] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The roles of transforming growth factor-β (TGF-β) receptor endocytosis in signaling have been investigated in numerous studies, mainly through the use of endocytosis inhibitory treatments, yielding conflicting results. Two potential sources for these discrepancies were the pleiotropic effects of a general blockade of specific internalization pathways and the scarce information on the regulation of the endocytosis of the signal-transducing type I TGF-β receptor (TβRI). Here, we employed extracellularly tagged myc-TβRI (wild type, truncation mutants, and a series of endocytosis-defective and endocytosis-enhanced mutants) to directly investigate the relationship between TβRI endocytosis and signaling. Our findings indicate that TβRI is targeted for constitutive clathrin-mediated endocytosis via a di-leucine (Leu(180)-Ile(181)) signal and an acidic cluster motif. Using Smad-dependent transcriptional activation assays and following Smad2/3 nuclear translocation in response to TGF-β stimulation, we show that TβRI endocytosis is dispensable for TGF-β signaling and may play a role in signal termination. Alanine replacement of Leu(180)-Ile(181) led to partial constitutive activation of TβRI, resulting in part from its retention at the plasma membrane and in part from potential alterations of TβRI regulatory interactions in the vicinity of the mutated residues.
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Affiliation(s)
- Keren E Shapira
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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29
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Ehrlich M, Gutman O, Knaus P, Henis YI. Oligomeric interactions of TGF-β and BMP receptors. FEBS Lett 2012; 586:1885-96. [PMID: 22293501 DOI: 10.1016/j.febslet.2012.01.040] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Revised: 01/15/2012] [Accepted: 01/19/2012] [Indexed: 10/14/2022]
Abstract
Transforming growth factor-β (TGF-β) and bone morphogenetic protein (BMP) cytokines participate in a multiplicity of ways in the regulation of numerous physiological and pathological processes. Their wide-ranging biological functions are controlled by several mechanisms, including regulation of transcription, complex formation among the signaling receptors (oligomerization) and with co-receptors, binding of the receptors to scaffolding proteins or their targeting to specific membrane domains. Here, we address the generation of TGF-β and BMP receptor homo- and hetero-oligomers and its roles as a mechanism capable of fast regulation of signaling by these crucial cytokines. We examine the available biochemical, biophysical and structural evidence for the ternary structure of these complexes, and the possible roles of homomeric and heteromeric receptor oligomers in signaling.
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Affiliation(s)
- Marcelo Ehrlich
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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30
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Eisenberg S, Wolfenson H, Berkovich R, Prior IA, Ehrlich M, Klafter J, Urbakh M, Henis YI. Quantitative FRAP Analysis Demonstrates that Raft Protein Clustering Alters N-Ras Depalmitoylation, Membrane Interactions and Activation Pattern. Biophys J 2012. [DOI: 10.1016/j.bpj.2011.11.201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022] Open
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31
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Heining E, Bhushan R, Paarmann P, Henis YI, Knaus P. Spatial segregation of BMP/Smad signaling affects osteoblast differentiation in C2C12 cells. PLoS One 2011; 6:e25163. [PMID: 21998639 PMCID: PMC3187766 DOI: 10.1371/journal.pone.0025163] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Accepted: 08/26/2011] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Bone morphogenetic proteins (BMPs) are involved in a plethora of cellular processes in embryonic development and adult tissue homeostasis. Signaling specificity is achieved by dynamic processes involving BMP receptor oligomerization and endocytosis. This allows for spatiotemporal control of Smad dependent and non-Smad pathways. In this study, we investigate the spatiotemporal regulation within the BMP-induced Smad transcriptional pathway. METHODOLOGY/PRINCIPAL FINDINGS Here we discriminate between Smad signaling events that are dynamin-dependent (i.e., require an intact endocytic pathway) and dynamin-independent. Inhibition of dynamin-dependent endocytosis in fluorescence microscopy and fractionation studies revealed a delay in Smad1/5/8 phosphorylation and nuclear translocation after BMP-2 stimulation of C2C12 cells. Using whole genome microarray and qPCR analysis, we identified two classes of BMP-2 induced genes that are differentially affected by inhibition of endocytosis. Thus, BMP-2 induced gene expression of Id1, Id3, Dlx2 and Hey1 is endocytosis-dependent, whereas BMP-2 induced expression of Id2, Dlx3, Zbtb2 and Krt16 is endocytosis-independent. Furthermore, we demonstrate that short term inhibition of endocytosis interferes with osteoblast differentiation as measured by alkaline phosphatase (ALP) production and qPCR analysis of osteoblast marker gene expression. CONCLUSIONS/SIGNIFICANCE Our study demonstrates that dynamin-dependent endocytosis is crucial for the concise spatial activation of the BMP-2 induced signaling cascade. Inhibition of endocytic processes during BMP-2 stimulation leads to altered Smad1/5/8 signaling kinetics and results in differential target gene expression. We show that interfering with the BMP-2 induced transcriptional network by endocytosis inhibition results in an attenuation of osteoblast differentiation. This implies that selective sensitivity of gene expression to endocytosis provides an additional mechanism for the cell to respond to BMP in a context specific manner. Moreover, we suggest a novel Smad dependent signal cascade induced by BMP-2, which does not require endocytosis.
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Affiliation(s)
- Eva Heining
- Institute for Chemistry and Biochemistry, Freie Universitaet Berlin, Berlin, Germany
| | - Raghu Bhushan
- Institute for Chemistry and Biochemistry, Freie Universitaet Berlin, Berlin, Germany
| | - Pia Paarmann
- Institute for Chemistry and Biochemistry, Freie Universitaet Berlin, Berlin, Germany
| | - Yoav I. Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Petra Knaus
- Institute for Chemistry and Biochemistry, Freie Universitaet Berlin, Berlin, Germany
- * E-mail:
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32
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Berkovich R, Wolfenson H, Eisenberg S, Ehrlich M, Weiss M, Klafter J, Henis YI, Urbakh M. Accurate quantification of diffusion and binding kinetics of non-integral membrane proteins by FRAP. Traffic 2011; 12:1648-57. [PMID: 21810156 DOI: 10.1111/j.1600-0854.2011.01264.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Non-integral membrane proteins frequently act as transduction hubs in vital signaling pathways initiated at the plasma membrane (PM). Their biological activity depends on dynamic interactions with the PM, which are governed by their lateral and cytoplasmic diffusion and membrane binding/unbinding kinetics. Accurate quantification of the multiple kinetic parameters characterizing their membrane interaction dynamics has been challenging. Despite a fair number of approximate fitting functions for analyzing fluorescence recovery after photobleaching (FRAP) data, no approach was able to cope with the full diffusion-exchange problem. Here, we present an exact solution and matlab fitting programs for FRAP with a stationary Gaussian laser beam, allowing simultaneous determination of the membrane (un)binding rates and the diffusion coefficients. To reduce the number of fitting parameters, the cytoplasmic diffusion coefficient is determined separately. Notably, our equations include the dependence of the exchange kinetics on the distribution of the measured protein between the PM and the cytoplasm, enabling the derivation of both k(on) and k(off) without prior assumptions. After validating the fitting function by computer simulations, we confirm the applicability of our approach to live-cell data by monitoring the dynamics of GFP-N-Ras mutants under conditions with different contributions of lateral diffusion and exchange to the FRAP kinetics.
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Affiliation(s)
- Ronen Berkovich
- School of Chemistry, Raymond and Beverley Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
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33
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Abstract
Rho of Plants (ROP) small G proteins function at discrete domains of the plasma and possibly endo membranes. ROPs are synthesized as soluble proteins and their attachment to membranes and partitioning in membrane microdomains are facilitated by the posttranslational lipid modifications prenylation and/or S-acylation. Based on their amino acid sequences, ROPs can be classified into two major subgroups: type-I ROPs terminate with a canonical CaaX box motif and are prenylated primarily by geranylgeranyltransferase-I (GGT-I) and to a lesser extent by farnesyltransferase (FT). Type-II ROPs terminate with a plant specific GC-CG box domain and are attached to the plasma membrane by stable S-acylation. In addition, type-I and possibly also type-II ROPs undergo activation dependent transient S-acylation in the G-domain and consequent partitioning into lipid rafts. Surprisingly, although geranylgeranylation is required for the membrane attachment of type-I ROPs and the γ subunits of heterotrimeric G proteins, Arabidopsis mutants lacking GGT-I function have a mild phenotype compared to wild type plants. The mild phenotype of the ggt-I mutants suggested that farnesylation by FT may compensate for the loss of GGT-I function and that possibly the prenylated type-I and S-acylated type-II ROPS have some overlapping functions. In a paper recently published in Plant Physiology we examined the role of the prenyl group type in type-I ROP function and membrane interaction dynamics and the functional redundancy between type-I and type-II ROPs. This study complements a second paper in which we examined the role of G-domain transient S-acylation in the membrane interaction dynamics and signaling by type-I ROPs. Together these two studies provide a framework for realizing the role of prenylation and S-acylation in subcellular targeting, membrane interaction dynamics and signaling by ROP GTPases.
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Affiliation(s)
- Nadav Sorek
- Energy Biosciences Institute; University of California at Berkeley; Berkeley, CA USA
- Department of Plant and Microbial Biology; University of California at Berkeley; Berkeley, CA USA
| | - Yoav I Henis
- Department of Neurobiology; George S. Wise Faculty of Life Sciences; Tel Aviv University; Tel Aviv, Israel
| | - Shaul Yalovsky
- Department of Molecular Biology and Ecology of Plants; George S. Wise Faculty of Life Sciences; Tel Aviv University; Tel Aviv, Israel
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Abstract
Focal adhesions (FAs) have key roles in the interaction of cells with the extracellular matrix (ECM) and in adhesion-mediated signaling. These dynamic, multi-protein structures sense the ECM both chemically and physically, and respond to external and internal forces by changing their size and signaling activity. However, this mechanosensitivity is still poorly understood at the molecular level. Here, we present direct evidence that actomyosin contractility regulates the molecular kinetics of FAs. We show that the molecular turnover of proteins within FAs is primarily regulated by their dissociation rate constant (k(off)), which is sensitive to changes in forces applied to the FA. We measured the early changes in k(off) values for three FA proteins (vinculin, paxillin and zyxin) upon inhibition of actomyosin-generated forces using two methods - high temporal resolution FRAP and direct measurement of FA protein dissociation in permeabilized cells. When myosin II contractility was inhibited, the k(off) values for all three proteins changed rapidly, in a highly protein-specific manner: dissociation of vinculin from FAs was facilitated, whereas dissociation of paxillin and zyxin was attenuated. We hypothesize that these early kinetic changes initiate FA disassembly by affecting the molecular turnover of FAs and altering their composition.
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Affiliation(s)
- Haguy Wolfenson
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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35
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Marom B, Heining E, Knaus P, Henis YI. Formation of stable homomeric and transient heteromeric bone morphogenetic protein (BMP) receptor complexes regulates Smad protein signaling. J Biol Chem 2011; 286:19287-96. [PMID: 21471205 DOI: 10.1074/jbc.m110.210377] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The type I and type II bone morphogenetic protein receptors (BMPRI and BMPRII) are present at the plasma membrane as monomers and homomeric and heteromeric complexes, which are modulated by ligand binding. The complexes of their extracellular domains with ligand were shown to form heterotetramers. However, the dynamics of the oligomeric interactions among the full-length receptors in live cell membranes were not explored, and the roles of BMP receptor homodimerization were unknown. Here, we investigated these issues by combining patching/immobilization of an epitope-tagged BMP receptor at the cell surface with measurements of the lateral diffusion of a co-expressed, differently tagged BMP receptor by fluorescence recovery after photobleaching (FRAP). These studies led to several novel conclusions. (a) All homomeric complexes (without or with BMP-2) were stable on the patch/FRAP time scale (minutes), whereas the heterocomplexes were transient, a difference that may affect signaling. (b) Patch/FRAP between HA- and myc-tagged BMPRII combined with competition by untagged BMPRIb showed that the heterocomplexes form at the expense of homodimers. (c) Stabilization of BMPRII·BMPRIb heterocomplexes (but not homomeric complexes) by IgG binding to same-tag receptors elevated phospho-Smad formation both without and with BMP-2. These findings suggest two mechanisms that may suppress the tendency of preformed BMP receptor hetero-oligomers to signal without ligand: (a) competition between homo- and heterocomplex formation, which reduces the steady-state level of the latter, and (b) the transient nature of the heterocomplexes, which limits the time during which BMPRI can be phosphorylated by BMPRII in the heterocomplex.
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Affiliation(s)
- Barak Marom
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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Sorek N, Gutman O, Bar E, Abu-Abied M, Feng X, Running MP, Lewinsohn E, Ori N, Sadot E, Henis YI, Yalovsky S. Differential effects of prenylation and s-acylation on type I and II ROPS membrane interaction and function. Plant Physiol 2011; 155:706-20. [PMID: 21139084 PMCID: PMC3032461 DOI: 10.1104/pp.110.166850] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Accepted: 11/30/2010] [Indexed: 05/21/2023]
Abstract
Prenylation primarily by geranylgeranylation is required for membrane attachment and function of type I Rho of Plants (ROPs) and Gγ proteins, while type II ROPs are attached to the plasma membrane by S-acylation. Yet, it is not known how prenylation affects ROP membrane interaction dynamics and what are the functional redundancy and specificity of type I and type II ROPs. Here, we have used the expression of ROPs in mammalian cells together with geranylgeranylation and CaaX prenylation-deficient mutants to answer these questions. Our results show that the mechanism of type II ROP S-acylation and membrane attachment is unique to plants and likely responsible for the viability of plants in the absence of CaaX prenylation activity. The prenylation of ROPs determines their steady-state distribution between the plasma membrane and the cytosol but has little effect on membrane interaction dynamics. In addition, the prenyl group type has only minor effects on ROP function. Phenotypic analysis of the CaaX prenylation-deficient pluripetala mutant epidermal cells revealed that type I ROPs affect cell structure primarily on the adaxial side, while type II ROPs are functional and induce a novel cell division phenotype in this genetic background. Taken together, our studies show how prenyl and S-acyl lipid modifications affect ROP subcellular distribution, membrane interaction dynamics, and function.
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Sorek N, Segev O, Gutman O, Bar E, Richter S, Poraty L, Hirsch JA, Henis YI, Lewinsohn E, Jürgens G, Yalovsky S. An S-acylation switch of conserved G domain cysteines is required for polarity signaling by ROP GTPases. Curr Biol 2010; 20:914-20. [PMID: 20451389 DOI: 10.1016/j.cub.2010.03.057] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Revised: 03/11/2010] [Accepted: 03/13/2010] [Indexed: 11/20/2022]
Abstract
Rho GTPases are master regulators of cell polarity. For their function, Rhos must associate with discrete plasma membrane domains. Rho of Plants (ROPs) or RACs comprise a single family. Prenylation and S-acylation of hypervariable domain cysteines of Ras and Rho GTPases are required for their function; however, lipid modifications in the G domain have never been reported. Reversible S-acylation involves the attachment of palmitate (C16:0) or other saturated lipids to cysteines through a thioester linkage and was implicated in the regulation of signaling. Here we show that transient S-acylation of Arabidopsis AtROP6 takes place on two conserved G domain cysteine residues, C21 and C156. C21 is relatively exposed and is accessible for modification, but C156 is not, implying that its S-acylation involves a conformational change. Fluorescence recovery after photobleaching beam-size analysis shows that S-acylation of AtROP6 regulates its membrane-association dynamics, and detergent-solubilization studies indicate that it regulates AtROP6 association with lipid rafts. Site-specific acylation-deficient AtROP6 mutants can bind and hydrolyze GTP but display compromised effects on polar cell growth, endocytic uptake of the tracer dye FM4-64, and distribution of reactive oxygen species. These data reveal an S-acylation switch that regulates Rho signaling.
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Affiliation(s)
- Nadav Sorek
- Department of Molecular Biology and Ecology of Plants, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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Wolfenson H, Henis YI, Geiger B, Bershadsky AD. The heel and toe of the cell's foot: a multifaceted approach for understanding the structure and dynamics of focal adhesions. ACTA ACUST UNITED AC 2010; 66:1017-29. [PMID: 19598236 DOI: 10.1002/cm.20410] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Focal adhesions (FAs) are large clusters of transmembrane receptors of the integrin family and a multitude of associated cytoplasmic "plaque" proteins, which connect the extracellular matrix-bound receptors with the actin cytoskeleton. The formation of nearly stationary FAs defines a boundary between the dense and highly dynamic actin network in lamellipodium and the sparser and more diverse cytoskeletal organization in the lamella proper, creating a template for the organization of the entire actin network. The major "mechanical" and "sensory" functions of FAs; namely, the nucleation and regulation of the contractile, myosin-II-containing stress fibers and the mechanosensing of external surfaces depend, to a major extent, on the dynamics of molecular components within FAs. A central element in FA regulation concerns the positive feedback loop, based on the most intriguing feature of FAs; that is, their dependence on mechanical tension developing by the growing stress fibers. FAs grow in response to such tension, and rapidly disassemble upon its relaxation. In this article, we address the mechanistic relationships between the process of FA development, maturation and dissociation and the dynamic molecular events, which take place in different regions of the FA, primarily in the distal end of this structure (the "toe") and the proximal "heel," and discuss the central role of local mechanical forces in orchestrating the complex interplay between FAs and the actin system.
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Affiliation(s)
- Haguy Wolfenson
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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Gutman O, Walliser C, Piechulek T, Gierschik P, Henis YI. Differential regulation of phospholipase C-beta2 activity and membrane interaction by Galphaq, Gbeta1gamma2, and Rac2. J Biol Chem 2010; 285:3905-3915. [PMID: 20007712 PMCID: PMC2823533 DOI: 10.1074/jbc.m109.085100] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Indexed: 01/15/2023] Open
Abstract
We combined fluorescence recovery after photobleaching (FRAP) beam-size analysis with biochemical assays to investigate the mechanisms of membrane recruitment and activation of phospholipase C-beta(2) (PLCbeta(2)) by G protein alpha(q) and betagamma dimers. We show that activation by alpha(q) and betagamma differ from activation by Rac2 and from each other. Stimulation by alpha(q) enhanced the plasma membrane association of PLCbeta(2), but not of PLCbeta(2)Delta, which lacks the alpha(q)-interacting region. Although alpha(q) resembled Rac2 in increasing the contribution of exchange to the FRAP of PLCbeta(2) and in enhancing its membrane association, the latter effect was weaker than with Rac2. Moreover, the membrane recruitment of PLCbeta(2) by alpha(q) occurred by enhancing PLCbeta(2) association with fast-diffusing (lipid-like) membrane components, whereas stimulation by Rac2 led to interactions with slow diffusing membrane sites. On the other hand, activation by betagamma shifted the FRAP of PLCbeta(2) and PLCbeta(2)Delta to pure lateral diffusion 3- to 5-fold faster than lipids, suggesting surfing-like diffusion along the membrane. We propose that these different modes of PLCbeta(2) membrane recruitment may accommodate contrasting functional needs to hydrolyze phosphatidylinositol 4,5-bisphosphate (PtdInsP(2)) in localized versus dispersed populations. PLCbeta(2) activation by Rac2, which leads to slow lateral diffusion and much faster exchange, recruits PLCbeta(2) to act locally on PtdInsP(2) at specific domains. Activation by alpha(q) leads to lipid-like diffusion of PLCbeta(2) accompanied by exchange, enabling the sampling of larger, yet limited, areas prior to dissociation. Finally, activation by betagamma recruits PLCbeta(2) to the membrane by transient interactions, leading to fast "surfing" diffusion along the membrane, sampling large regions for dispersed PtdInsP(2) populations.
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Affiliation(s)
- Orit Gutman
- From the Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel, and
| | - Claudia Walliser
- the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Thomas Piechulek
- the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Peter Gierschik
- the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
| | - Yoav I Henis
- From the Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel, and.
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40
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Schwappacher R, Weiske J, Heining E, Ezerski V, Marom B, Henis YI, Huber O, Knaus P. Novel crosstalk to BMP signalling: cGMP-dependent kinase I modulates BMP receptor and Smad activity. EMBO J 2009; 28:1537-50. [PMID: 19424179 DOI: 10.1038/emboj.2009.103] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Accepted: 03/20/2009] [Indexed: 01/09/2023] Open
Abstract
Integration of multiple signals into the canonical BMP/Smad pathway poses a big challenge during the course of embryogenesis and tissue homeostasis. Here, we show that cyclic guanosine 3',5'-monophosphate (cGMP)-dependent kinase I (cGKI) modulates BMP receptors and Smads, providing a novel mechanism enhancing BMP signalling. cGKI, a key mediator of vasodilation and hypertension diseases, interacts with and phosphorylates the BMP type II receptor (BMPRII). In response to BMP-2, cGKI then dissociates from the receptors, associates with activated Smads, and undergoes nuclear translocation. In the nucleus, cGKI binds with Smad1 and the general transcription factor TFII-I to promoters of BMP target genes such as Id1 to enhance transcriptional activation. Accordingly, cGKI has a dual function in BMP signalling: (1) it modulates BMP receptor/Smad activity at the plasma membrane and (2) after redistribution to the nucleus, it further regulates transcription as a nuclear co-factor for Smads. Consequently, cellular defects caused by mutations in BMPRII, found in pulmonary arterial hypertension patients, were compensated through cGKI, supporting the positive action of cGKI on BMP-induced Smad signalling downstream of the receptors.
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41
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Wolfenson H, Lubelski A, Regev T, Klafter J, Henis YI, Geiger B. A role for the juxtamembrane cytoplasm in the molecular dynamics of focal adhesions. PLoS One 2009; 4:e4304. [PMID: 19172999 PMCID: PMC2627934 DOI: 10.1371/journal.pone.0004304] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Accepted: 12/12/2008] [Indexed: 01/01/2023] Open
Abstract
Focal adhesions (FAs) are specialized membrane-associated multi-protein complexes that link the cell to the extracellular matrix and play crucial roles in cell-matrix sensing. Considerable information is available on the complex molecular composition of these sites, yet the regulation of FA dynamics is largely unknown. Based on a combination of FRAP studies in live cells, with in silico simulations and mathematical modeling, we show that the FA plaque proteins paxillin and vinculin exist in four dynamic states: an immobile FA-bound fraction, an FA-associated fraction undergoing exchange, a juxtamembrane fraction experiencing attenuated diffusion, and a fast-diffusing cytoplasmic pool. The juxtamembrane region surrounding FAs displays a gradient of FA plaque proteins with respect to both concentration and dynamics. Based on these findings, we propose a new model for the regulation of FA dynamics in which this juxtamembrane domain acts as an intermediary layer, enabling an efficient regulation of FA formation and reorganization.
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Affiliation(s)
- Haguy Wolfenson
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Ariel Lubelski
- School of Chemistry, Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Tamar Regev
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Joseph Klafter
- School of Chemistry, Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel
- Freiburg Institute for Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany
| | - Yoav I. Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
- * E-mail: (YH); (BG)
| | - Benjamin Geiger
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
- * E-mail: (YH); (BG)
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Rechtman MM, Nakaryakov A, Shapira KE, Ehrlich M, Henis YI. Different domains regulate homomeric and heteromeric complex formation among type I and type II transforming growth factor-beta receptors. J Biol Chem 2009; 284:7843-52. [PMID: 19147499 DOI: 10.1074/jbc.m809215200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Transforming growth factor-beta (TGF-beta) binds to and signals via two serine-threonine kinase receptors, type I (TbetaRI) and type II (TbetaRII). The oligomerization of TGF-beta receptors modulates ligand binding and receptor trafficking and may contribute to signal diversification. However, numerous features of the molecular domains that determine the homo- and hetero-oligomerization of full-length receptors at the cell surface and the mode of these interactions remain unclear. Here, we address these questions through computerized immunofluorescence co-patching and patch/fluorescence recovery after photobleaching measurements of different combinations of epitope-tagged receptors and their mutants in live cells. We show that TbetaRI and TbetaRII are present on the plasma membrane both as monomers and homo- and hetero-oligomers. The homodimerization of TbetaRII depends on a cytoplasmic juxtamembrane region (amino acid residues 200-220). In contrast, the cytoplasmic domain of TbetaRI is dispensable for its homodimerization. TbetaRI.TbetaRII hetero-oligomerization depends on the cytoplasmic domain of TbetaRI and on a C-terminal region of TbetaRII (residues 419-565). TGF-beta1 elevates TbetaRII homodimerization to some degree and strongly enhances TbetaRI.TbetaRII heteromeric complex formation. Both ligand-induced effects depend on the region encompassed between residues 200-242 of TbetaRII. Furthermore, the kinase activity of TbetaRI is also necessary for the latter effect. All forms of the homo- and hetero-oligomers, whether constitutively present on the membrane or formed upon TGF-beta1 stimulation, were stable in the time-scale of our patch/FRAP measurements. We suggest that the different forms of receptor oligomerization may serve as a basis for the heterogeneity of TGF-beta signaling responses.
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Affiliation(s)
- Maya Mouler Rechtman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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Abstract
Ras proteins have become paradigms for isoform- and compartment-specific signaling. Recent work has shown that Ras isoforms are differentially distributed within cell surface signaling nanoclusters and on endomembranous compartments. The critical feature regulating Ras protein localization and isoform-specific functions is the C-terminal hypervariable region (HVR). In this review we discuss the differential post-translational modifications and reversible targeting functions of Ras isoform HVR motifs. We describe how compartmentalized Ras signaling has specific functional consequences and how cell surface signaling nanoclusters generate precise signaling outputs.
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Affiliation(s)
- Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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44
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Malka Y, Hornakova T, Royer Y, Knoops L, Renauld JC, Constantinescu SN, Henis YI. Ligand-independent homomeric and heteromeric complexes between interleukin-2 or -9 receptor subunits and the gamma chain. J Biol Chem 2008; 283:33569-77. [PMID: 18829468 DOI: 10.1074/jbc.m803125200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Signaling via interleukin-2 (IL-2) and interleukin-9 receptors (IL-2R and IL-9R) involves heteromeric interactions between specific interleukin receptor subunits, which bind Janus kinase 1 (JAK1) and the JAK3 binding common gamma chain (gamma c). The potential existence and roles of homomeric and heteromeric complexes before ligand binding and their modulation by ligand and JAK3 are unclear. Using computerized antibody-mediated immunofluorescence co-patching of epitope-tagged receptors at the surface of live cells, we demonstrate that IL-2Rbeta, IL-9Ralpha, and gamma c each display a significant fraction of ligand-independent homomeric complexes (24-28% co-patching), whereas control co-patching levels with unrelated receptors are very low (7%). Heteromeric complex formation of IL2-Rbeta or IL-9Ralpha with gamma c is also observed in the absence of ligand (15-30%). Ligand binding increases this hetero-oligomerization 2-fold but does not affect homo-oligomerization. Co-expression of IL-2Ralpha does not affect the hetero-oligomerization of IL-2Rbeta and gamma c. Recruitment of gamma c into heterocomplexes is partly at the expense of its homo-oligomerization, suggesting that a functional role of the latter may be to keep the receptors inactive in the absence of ligand. At the same time, the preformed complexes between gamma c and IL-2Rbeta or IL-9Ralpha promote signaling by the JAK3 A572V mutant without ligand, supporting a pathophysiological role for the constitutive oligomerization in triggering ligand-independent activation of JAK3 (and perhaps other JAK mutants) mutants identified in several human cancers.
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Affiliation(s)
- Yaniv Malka
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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45
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Eisenberg S, Giehl K, Henis YI, Ehrlich M. Differential interference of chlorpromazine with the membrane interactions of oncogenic K-Ras and its effects on cell growth. J Biol Chem 2008; 283:27279-88. [PMID: 18693247 DOI: 10.1074/jbc.m804589200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Membrane anchorage of Ras proteins is important for their signaling and oncogenic potential. K-Ras4B (K-Ras), the Ras isoform most often mutated in human cancers, is the only Ras isoform where a polybasic motif contributes essential electrostatic interactions with the negatively charged cytoplasmic leaflet. Here we studied the effects of the cationic amphiphilic drug chlorpromazine (CPZ) on the membrane association of oncogenic K-Ras(G12V), cell proliferation, and apoptosis. Combining live cell microscopy, FRAP beam size analysis, and cell fractionation studies, we show that CPZ reduces the association of GFP-K-Ras(G12V) with the plasma membrane and increases its exchange between plasma membrane and cytoplasmic pools. These effects appear to depend on electrostatic interactions because the membrane association of another related protein that has a membrane-interacting polybasic cluster (Rac1(G12V)) was also affected, whereas that of H-Ras was not. The weakened association with the plasma membrane led to a higher fraction of GFP-K-Ras(G12V) in the cytoplasm and in internal membranes, accompanied by either cell cycle arrest (PANC-1 cells) or apoptosis (Rat-1 fibroblasts), the latter being in correlation with the targeting of K-Ras(G12V) to mitochondria. In accord with these results, CPZ compromised the transformed phenotype of PANC-1 cells, as indicated by inhibition of cell migration and growth in soft agar.
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Affiliation(s)
- Sharon Eisenberg
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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Shvartsman DE, Donaldson JC, Diaz B, Gutman O, Martin GS, Henis YI. Src kinase activity and SH2 domain regulate the dynamics of Src association with lipid and protein targets. ACTA ACUST UNITED AC 2007; 178:675-86. [PMID: 17698610 PMCID: PMC2064473 DOI: 10.1083/jcb.200701133] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Src functions depend on its association with the plasma membrane and with specific membrane-associated assemblies. Many aspects of these interactions are unclear. We investigated the functions of kinase, SH2, and SH3 domains in Src membrane interactions. We used FRAP beam-size analysis in live cells expressing a series of c-Src–GFP proteins with targeted mutations in specific domains together with biochemical experiments to determine whether the mutants can generate and bind to phosphotyrosyl proteins. Wild-type Src displays lipid-like membrane association, whereas constitutively active Src-Y527F interacts transiently with slower-diffusing membrane-associated proteins. These interactions require Src kinase activity and SH2 binding, but not SH3 binding. Furthermore, overexpression of paxillin, an Src substrate with a high cytoplasmic population, competes with membrane phosphotyrosyl protein targets for binding to activated Src. Our observations indicate that the interactions of Src with lipid and protein targets are dynamic and that the kinase and SH2 domain cooperate in the membrane targeting of Src.
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Affiliation(s)
- Dmitry E Shvartsman
- Department of Neurobiochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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47
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Kalo E, Buganim Y, Shapira KE, Besserglick H, Goldfinger N, Weisz L, Stambolsky P, Henis YI, Rotter V. Mutant p53 attenuates the SMAD-dependent transforming growth factor beta1 (TGF-beta1) signaling pathway by repressing the expression of TGF-beta receptor type II. Mol Cell Biol 2007; 27:8228-42. [PMID: 17875924 PMCID: PMC2169171 DOI: 10.1128/mcb.00374-07] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Both transforming growth factor beta (TGF-beta) and p53 have been shown to control normal cell growth. Acquired mutations either in the TGF-beta signaling pathway or in the p53 protein were shown to induce malignant transformation. Recently, cross talk between wild-type p53 and the TGF-beta pathway was observed. The notion that mutant p53 interferes with the wild-type p53-induced pathway and acts by a "gain-of-function" mechanism prompted us to investigate the effect of mutant p53 on the TGF-beta-induced pathway. In this study, we show that cells expressing mutant p53 lost their sensitivity to TGF-beta1, as observed by less cell migration and a reduction in wound healing. We found that mutant p53 attenuates TGF-beta1 signaling. This was exhibited by a reduction in SMAD2/3 phosphorylation and an inhibition of both the formation of SMAD2/SMAD4 complexes and the translocation of SMAD4 to the cell nucleus. Furthermore, we found that mutant p53 attenuates the TGF-beta1-induced transcription activity of SMAD2/3 proteins. In searching for the mechanism that underlies this attenuation, we found that mutant p53 reduces the expression of TGF-beta receptor type II. These data provide important insights into the molecular mechanisms that underlie mutant p53 "gain of function" pertaining to the TGF-beta signaling pathway.
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Affiliation(s)
- Eyal Kalo
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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48
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Abstract
The complex dynamic structure of the plasma membrane plays critical roles in cellular signaling; interactions with the membrane lipid milieu, spatial segregation within and between cellular membranes and/or targeting to specific membrane-associated scaffolds are intimately involved in many signal transduction pathways. In this review, we focus on the membrane interactions of Ras proteins. These small GTPases play central roles in the regulation of cell growth and proliferation, and their excessive activation is commonly encountered in human tumors. Ras proteins associate with the membrane continuously via C-terminal lipidation and additional interactions in both their inactive and active forms; this association, as well as the targeting of specific Ras isoforms to plasma membrane microdomains and to intracellular organelles, have recently been implicated in Ras signaling and oncogenic potential. We discuss biochemical and biophysical evidence for the roles of specific domains of Ras proteins in mediating their association with the plasma membrane, and consider the potential effects of lateral segregation and interactions with membrane-associated protein assemblies on the signaling outcomes.
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Affiliation(s)
- Sharon Eisenberg
- Department of Neurobiochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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49
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Murphy SJ, Shapira KE, Henis YI, Leof EB. A unique element in the cytoplasmic tail of the type II transforming growth factor-beta receptor controls basolateral delivery. Mol Biol Cell 2007; 18:3788-99. [PMID: 17634290 PMCID: PMC1995729 DOI: 10.1091/mbc.e06-10-0930] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Transforming growth factor (TGF)-beta receptors stimulate diverse signaling processes that control a wide range of biological responses. In polarized epithelia, the TGFbeta type II receptor (T2R) is localized at the basolateral membranes. Sequential cytoplasmic truncations resulted in receptor missorting to apical surfaces, and they indicated an essential targeting element(s) near the receptor's C terminus. Point mutations in the full-length receptor confirmed this prediction, and a unique basolateral-targeting region was elucidated between residues 529 and 538 (LTAxxVAxxR) that was distinct, but colocalized within a clinically significant signaling domain essential for TGFbeta-dependent activation of the Smad2/3 cascade. Transfer of a terminal 84 amino-acid fragment, containing the LTAxxVAxxR element, to the apically sorted influenza hemagglutinin (HA) protein was dominant and directed basolateral HA expression. Although delivery to the basolateral surfaces was direct and independent of any detectable transient apical localization, fluorescence recovery after photobleaching demonstrated similar mobility for the wild-type receptor and a missorted mutant lacking the targeting motif. This latter finding excludes the possibility that the domain acts as a cell membrane retention signal, and it supports the hypothesis that T2R sorting occurs from an intracellular compartment.
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Affiliation(s)
- Stephen J. Murphy
- *Thoracic Diseases Research Unit, Department of Biochemistry and Molecular Biology and Mayo Clinic Cancer Center, Mayo Clinic College of Medicine, Rochester, MN 55905; and
| | - Keren E. Shapira
- Department of Neurobiochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Yoav I. Henis
- Department of Neurobiochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Edward B. Leof
- *Thoracic Diseases Research Unit, Department of Biochemistry and Molecular Biology and Mayo Clinic Cancer Center, Mayo Clinic College of Medicine, Rochester, MN 55905; and
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50
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Henis YI, Rotblat B, Kloog Y. FRAP beam-size analysis to measure palmitoylation-dependent membrane association dynamics and microdomain partitioning of Ras proteins. Methods 2006; 40:183-90. [PMID: 17012031 DOI: 10.1016/j.ymeth.2006.02.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2006] [Accepted: 02/24/2006] [Indexed: 10/24/2022] Open
Abstract
Motions of membrane-associated proteins within and between membranes are essential for many cellular functions. We describe the application of fluorescence recovery after photobleaching (FRAP) beam-size analysis to investigate the role of palmitoylation in the membrane targeting and membrane association dynamics of H-Ras. The method described distinguishes between FRAP by lateral diffusion and by cytoplasmic exchange, and enables to obtain an estimate of the membrane affinity in live cells. These studies show distinct roles for the two palmitoylation sites (Cys181 and Cys184) on H-Ras, with different effects on membrane affinity and microlocalization.
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Affiliation(s)
- Yoav I Henis
- Department of Neurobiochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
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