1
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Huang L, Thiex NW, Lou J, Ahmad G, An W, Low-Nam ST, Kerkvliet JG, Band H, Hoppe AD. The ubiquitin ligases Cbl and Cbl-b regulate macrophage growth by controlling CSF-1R import into macropinosomes. Mol Biol Cell 2024; 35:ar38. [PMID: 38170572 PMCID: PMC10916879 DOI: 10.1091/mbc.e23-09-0345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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] [Received: 09/05/2023] [Revised: 12/11/2023] [Accepted: 12/18/2023] [Indexed: 01/05/2024] Open
Abstract
The ubiquitination of transmembrane receptors regulates endocytosis, intracellular traffic, and signal transduction. Bone marrow-derived macrophages from myeloid Cbl-/- and Cbl-b-/- double knockout (DKO) mice display sustained proliferation mirroring the myeloproliferative disease that these mice succumb to. Here, we found that the ubiquitin ligases Cbl and Cbl-b have overlapping functions for controlling the endocytosis and intracellular traffic of the CSF-1R. DKO macrophages displayed complete loss of ubiquitination of the CSF-1R whereas partial ubiquitination was observed for either single Cbl-/- or Cbl-b-/- macrophages. Unlike wild type, DKO macrophages were immortal and displayed slower CSF-1R internalization, elevated AKT signaling, and a failure to transport the CSF-1R into the lumen of nascent macropinosomes, leaving its cytoplasmic region available for signaling. CSF-1R degradation depended upon lysosomal vATPase activity in both WT and DKO macrophages, with this degradation confined to macropinosomes in WT but occurring in distributed/tubular lysosomes in DKO cells. RNA-sequencing comparison of Cbl-/-, Cbl-b-/- and DKO macrophages indicated that while the overall macrophage transcriptional program remained intact, DKO macrophages had alterations in gene expression associated with growth factor signaling, cell cycle, inflammation and senescence. Cbl-b-/- had minimal effect on the transcriptional program whereas Cbl-/- led to more alternations but only DKO macrophages demonstrated substantial changes in the transcriptome, suggesting overlapping but unique functions for the two Cbl-family members. Thus, Cbl/Cbl-b-mediated ubiquitination of CSF-1R regulates its endocytic fate, constrains inflammatory gene expression, and regulates signaling for macrophage proliferation.
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Affiliation(s)
- Lu Huang
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD 57007
- BioSNTR, Brookings, SD 57007
| | - Natalie W. Thiex
- Department of Biology and Microbiology, South Dakota State University, Brookings, SD 57007
- BioSNTR, Brookings, SD 57007
| | - Jieqiong Lou
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD 57007
| | - Gulzar Ahmad
- Eppley Institute for Research in Cancer and Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198
| | - Wei An
- Eppley Institute for Research in Cancer and Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198
| | - Shalini T. Low-Nam
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD 57007
| | - Jason G. Kerkvliet
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD 57007
- BioSNTR, Brookings, SD 57007
| | - Hamid Band
- Eppley Institute for Research in Cancer and Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198
| | - Adam D. Hoppe
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD 57007
- BioSNTR, Brookings, SD 57007
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2
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McAffee DB, O’Dair MK, Lin JJ, Low-Nam ST, Wilhelm KB, Kim S, Morita S, Groves JT. Discrete LAT condensates encode antigen information from single pMHC:TCR binding events. Nat Commun 2022; 13:7446. [PMID: 36460640 PMCID: PMC9718779 DOI: 10.1038/s41467-022-35093-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Accepted: 11/17/2022] [Indexed: 12/05/2022] Open
Abstract
LAT assembly into a two-dimensional protein condensate is a prominent feature of antigen discrimination by T cells. Here, we use single-molecule imaging techniques to resolve the spatial position and temporal duration of each pMHC:TCR molecular binding event while simultaneously monitoring LAT condensation at the membrane. An individual binding event is sufficient to trigger a LAT condensate, which is self-limiting, and neither its size nor lifetime is correlated with the duration of the originating pMHC:TCR binding event. Only the probability of the LAT condensate forming is related to the pMHC:TCR binding dwell time. LAT condenses abruptly, but after an extended delay from the originating binding event. A LAT mutation that facilitates phosphorylation at the PLC-γ1 recruitment site shortens the delay time to LAT condensation and alters T cell antigen specificity. These results identify a function for the LAT protein condensation phase transition in setting antigen discrimination thresholds in T cells.
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Affiliation(s)
- Darren B. McAffee
- grid.47840.3f0000 0001 2181 7878Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720 USA
| | - Mark K. O’Dair
- grid.47840.3f0000 0001 2181 7878Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720 USA
| | - Jenny J. Lin
- grid.47840.3f0000 0001 2181 7878Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720 USA
| | - Shalini T. Low-Nam
- grid.47840.3f0000 0001 2181 7878Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720 USA
| | - Kiera B. Wilhelm
- grid.47840.3f0000 0001 2181 7878Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720 USA
| | - Sungi Kim
- grid.47840.3f0000 0001 2181 7878Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720 USA
| | - Shumpei Morita
- grid.47840.3f0000 0001 2181 7878Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720 USA
| | - Jay T. Groves
- grid.47840.3f0000 0001 2181 7878Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720 USA ,grid.59025.3b0000 0001 2224 0361Institute for Digital Molecular Analytics and Science, Nanyang Technological University, 59 Nanyang Drive, Singapore, 636921 Singapore
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3
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Curtis RW, Scrudders KL, Ulcickas JRW, Simpson GJ, Low-Nam ST, Chmielewski J. Supramolecular Assembly of His-Tagged Fluorescent Protein Guests within Coiled-Coil Peptide Crystal Hosts: Three-Dimensional Ordering and Protein Thermal Stability. ACS Biomater Sci Eng 2022; 8:1860-1866. [PMID: 35377599 PMCID: PMC9840175 DOI: 10.1021/acsbiomaterials.2c00155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The use of biomaterials for the inclusion and stabilization of biopolymers is an ongoing challenge. Herein, we disclose three-dimensional (3D) coiled-coil peptide crystals with metal ions that include and overgrow His-tagged fluorescent proteins within the crystal. The protein guests are found within two symmetry-related growth sectors of the crystalline host that are associated with faces of the growing crystal that display ligands for metal ions. The fluorescent proteins are included within this "hourglass" region of the crystals at a notably high level, display order within the crystal hosts, and demonstrate sufficiently tight packing to enable energy transfer between a donor-acceptor pair. His-tagged fluorescent proteins display remarkable thermal stability to denaturation over extended periods of time (days) at high temperatures when within the crystals. Ultimately, this strategy may prove useful for the prolonged storage of thermally sensitive biopolymer guests within a 3D crystalline matrix.
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Affiliation(s)
- Ryan W. Curtis
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, United States
| | - Kevin L. Scrudders
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, United States
| | - James R. W. Ulcickas
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, United States
| | - Garth J. Simpson
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, United States
| | - Shalini T. Low-Nam
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, United States
| | - Jean Chmielewski
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, United States
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4
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Lin JJ, O'Donoghue GP, Wilhelm KB, Coyle MP, Low-Nam ST, Fay NC, Alfieri KN, Groves JT. Membrane Association Transforms an Inert Anti-TCRβ Fab' Ligand into a Potent T Cell Receptor Agonist. Biophys J 2020; 118:2879-2893. [PMID: 32407684 DOI: 10.1016/j.bpj.2020.04.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 03/09/2020] [Accepted: 04/13/2020] [Indexed: 12/27/2022] Open
Abstract
The natural peptide-major histocompatibility complex (pMHC) ligand for T cell receptors (TCRs) is inactive from solution yet capable of activating T cells at single-molecule levels when membrane-associated. This distinctive feature stems from the mechanism of TCR activation, which is thought to involve steric phosphatase exclusion as well as direct mechanical forces. It is possible to defeat this mechanism and activate T cells with solution ligands by cross-linking pMHC or using multivalent antibodies to TCR. However, these widely used strategies activate TCRs through a nonphysiological mechanism and can produce different activation profiles than natural, monovalent, membrane-associated pMHC. Here, we introduce a strictly monovalent anti-TCRβ H57 Fab' ligand that, when coupled to a supported lipid bilayer via DNA complementation, triggers TCRs and activates nuclear translocation of the transcription factor nuclear factor of activated T cells (NFAT) with a similar potency to pMHC in primary murine T cells. Importantly, like monovalent pMHC and unlike bivalent antibodies, monovalent Fab'-DNA triggers TCRs only when physically coupled to the membrane, and only around 100 individual Fab':TCR interactions are necessary to stimulate early T cell activation.
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Affiliation(s)
- Jenny J Lin
- Department of Chemistry, University of California, Berkeley, Berkeley, California
| | - Geoff P O'Donoghue
- Department of Chemistry, University of California, Berkeley, Berkeley, California.
| | - Kiera B Wilhelm
- Department of Chemistry, University of California, Berkeley, Berkeley, California
| | - Michael P Coyle
- Department of Chemistry, University of California, Berkeley, Berkeley, California.
| | - Shalini T Low-Nam
- Department of Chemistry, University of California, Berkeley, Berkeley, California
| | - Nicole C Fay
- Department of Molecular and Cellular Biology, University of California, Berkeley, Berkeley, California
| | - Katherine N Alfieri
- Department of Chemistry, University of California, Berkeley, Berkeley, California
| | - Jay T Groves
- Department of Chemistry, University of California, Berkeley, Berkeley, California.
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5
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McAffee DB, Low-Nam ST, Lin JJY, Alvarez SA, Hansen SD, Groves JT. Single pMHC:TCR Binding Events Precipitate LAT Assemblies Capable of Spatially Decoupling from the Originating Ligand. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.2858] [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: 10/27/2022] Open
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6
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Low-Nam ST, Lin JJY, McAffee DB, Alvarez SA, Hansen SD, Roybal KT, Groves JT. Beyond the TCR, Antigen Discrimination in T Cells Continues in the LAT:GRB2:SOS Protein Condensate. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.2856] [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: 11/24/2022] Open
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7
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Wilhelm KB, Coyle MP, O'Donoghue GP, Lin JJY, Low-Nam ST, Groves JT. A Membrane-Activated, Universal T-Cell Receptor Agonist. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.2857] [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: 11/24/2022] Open
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8
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Lin JJY, Low-Nam ST, Alfieri KN, McAffee DB, Fay NC, Groves JT. Mapping the stochastic sequence of individual ligand-receptor binding events to cellular activation: T cells act on the rare events. Sci Signal 2019; 12:12/564/eaat8715. [PMID: 30647147 DOI: 10.1126/scisignal.aat8715] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
T cell receptor (TCR) binding to agonist peptide major histocompatibility complex (pMHC) triggers signaling events that initiate T cell responses. This system is remarkably sensitive, requiring only a few binding events to successfully activate a cellular response. On average, activating pMHC ligands exhibit mean dwell times of at least a few seconds when bound to the TCR. However, a T cell accumulates pMHC-TCR interactions as a stochastic series of discrete, single-molecule binding events whose individual dwell times are broadly distributed. With activation occurring in response to only a handful of such binding events, individual cells are unlikely to experience the average binding time. Here, we mapped the ensemble of pMHC-TCR binding events in space and time while simultaneously monitoring cellular activation. Our findings revealed that T cell activation hinges on rare, long-dwell time binding events that are an order of magnitude longer than the average agonist pMHC-TCR dwell time. Furthermore, we observed that short pMHC-TCR binding events that were spatially correlated and temporally sequential led to cellular activation. These observations indicate that T cell antigen discrimination likely occurs by sensing the tail end of the pMHC-TCR binding dwell time distribution rather than its average properties.
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Affiliation(s)
- Jenny J Y Lin
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Shalini T Low-Nam
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Katherine N Alfieri
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Darren B McAffee
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Nicole C Fay
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Jay T Groves
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA.
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9
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Thakar D, Low-Nam ST, Groves JT, Weaver VM. Abstract 5912: Tumor micoenvironment modulates RTK signaling. Cancer Res 2017. [DOI: 10.1158/1538-7445.am2017-5912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Receptor tyrosine kinases (RTKs) and their associated signaling molecules are mutated or dysregulated in many aggressive cancers such as non-small cell lung carcinoma (NSCLC), breast cancer, and colorectal cancer. Despite therapeutic interventions such as tyrosine kinase inhibitors (TKI) that target RTKs, majority of patients develop resistance even after initial tumor regression. Although clinical studies suggest sequential treatments with TKI, chemotherapy, and radiation can eliminate most cancer cells, resistance inevitably emerges (Sequist, et al., Sci Trans Med, 2011). We demonstrated that alterations in the extracellular matrix (ECM) correlate with cancer progression and that RTK signaling is subject to spatiotemporal regulation (Paszek, et al., Cancer Cell, 2005.; Salaita, et al., Science, 2010). Thus, geometric and mechanical properties of the ECM may directly modulate RTK signaling. Here, we use silicone gel substrates that exhibit tunable stiffness in the physiological range (100s Pa - 100s kPa) to measure RTK-adaptor protein interactions in mammary epithelial cells (MECs; MCF10A) (Ou, et al. Integ. Biol., 2016). These gels are compatible with total internal reflection fluorescence (TIRF) imaging and enable single molecule detection of activated RTK phosphotyrosine residues via recruitment of Grb2 tagged with the fluorescent protein mEos3.2. We demonstrate a spectrum of Grb2 behaviors that are determined by the stiffness of the substrate. This indicates that the same receptor is capable of different signaling activities that are dictated by material properties. These new insights create opportunities to target the tumor microenvironment to address RTK inhibitor resistance and metastasis in cancer patients and to develop effective therapeutic strategies for better prognosis and prolonged patient survival.
Citation Format: Dhruv Thakar, Shalini T. Low-Nam, Jay T. Groves, Valerie M. Weaver. Tumor micoenvironment modulates RTK signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5912. doi:10.1158/1538-7445.AM2017-5912
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Affiliation(s)
- Dhruv Thakar
- 1University of California San Francisco, San Francisco, CA
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10
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Lou J, Low-Nam ST, Kerkvliet JG, Hoppe AD. Delivery of CSF-1R to the lumen of macropinosomes promotes its destruction in macrophages. J Cell Sci 2014; 127:5228-39. [PMID: 25335894 DOI: 10.1242/jcs.154393] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Activation of the macrophage colony stimulating factor-1 receptor (CSF-1R) by CSF-1 stimulates pronounced macropinocytosis and drives proliferation of macrophages. Although the role of macropinocytosis in CSF-1R signaling remains unknown, we show here that, despite internalizing large quantities of plasma membrane, macropinosomes contribute little to the internalization of the CSF-1-CSF-1R complex. Rather, internalization of the CSF-1R in small endocytic vesicles that are sensitive to clathrin disruption, outcompetes macropinosomes for CSF-1R endocytosis. Following internalization, small vesicles carrying the CSF-1R underwent homotypic fusion and then trafficked to newly formed macropinosomes bearing Rab5. As these macropinosomes matured, acquiring Rab7, the CSF-1R was transported into their lumen and degraded. Inhibition of macropinocytosis delayed receptor degradation despite no disruption to CSF-1R endocytosis. These data indicate that CSF-1-stimulated macropinosomes are sites of multivesicular body formation and accelerate CSF-1R degradation. Furthermore, we demonstrate that macropinocytosis and cell growth have a matching dose dependence on CSF-1, suggesting that macropinosomes might be a central mechanism coupling CSF-1R signaling and macrophage growth.
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Affiliation(s)
- Jieqiong Lou
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, 57007 SD, USA
| | - Shalini T Low-Nam
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, 57007 SD, USA
| | - Jason G Kerkvliet
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, 57007 SD, USA
| | - Adam D Hoppe
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, 57007 SD, USA
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11
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Pryor MM, Low-Nam ST, Halász AM, Lidke DS, Wilson BS, Edwards JS. Dynamic transition states of ErbB1 phosphorylation predicted by spatial stochastic modeling. Biophys J 2014; 105:1533-43. [PMID: 24048005 DOI: 10.1016/j.bpj.2013.07.056] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 07/08/2013] [Accepted: 07/29/2013] [Indexed: 11/25/2022] Open
Abstract
ErbB1 overexpression is strongly linked to carcinogenesis, motivating better understanding of erbB1 dimerization and activation. Recent single-particle-tracking data have provided improved measures of dimer lifetimes and strong evidence that transient receptor coconfinement promotes repeated interactions between erbB1 monomers. Here, spatial stochastic simulations explore the potential impact of these parameters on erbB1 phosphorylation kinetics. This rule-based mathematical model incorporates structural evidence for conformational flux of the erbB1 extracellular domains, as well as asymmetrical orientation of erbB1 cytoplasmic kinase domains during dimerization. The asymmetric dimer model considers the theoretical consequences of restricted transactivation of erbB1 receptors within a dimer, where the N-lobe of one monomer docks with the C-lobe of the second monomer and triggers its catalytic activity. The dynamic nature of the erbB1 phosphorylation state is shown by monitoring activation states of individual monomers as they diffuse, bind, and rebind after ligand addition. The model reveals the complex interplay between interacting liganded and nonliganded species and the influence of their distribution and abundance within features of the membrane landscape.
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Affiliation(s)
- Meghan McCabe Pryor
- Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico
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12
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Valley CC, Low-Nam ST, Steinkamp MP, Wilson BS, Lidke KA, Lidke DS. Single Molecule Imaging Reveals that Activating Kinase Domain Mutations Reduce EGFR Mobility and Enhance Dimerization. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.633] [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: 11/17/2022] Open
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13
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Low-Nam ST, Kerkvliet JG, Cheng AT, Drubin DG, Hoppe AD. Polarized-Tirf-Based Monitoring of Sub-Resolution Membrane Curvature Dynamics during Clathrin-Mediated Endocytosis. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.3424] [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: 10/27/2022] Open
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14
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Low-Nam ST, Lidke KA, Cutler PJ, Roovers RC, van Bergen en Henegouwen PMP, Wilson BS, Lidke DS. ErbB1 dimerization is promoted by domain co-confinement and stabilized by ligand binding. Nat Struct Mol Biol 2011; 18:1244-9. [PMID: 22020299 PMCID: PMC3210321 DOI: 10.1038/nsmb.2135] [Citation(s) in RCA: 197] [Impact Index Per Article: 15.2] [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: 01/18/2011] [Accepted: 08/09/2011] [Indexed: 12/11/2022]
Abstract
The extent to which ligand occupancy and dimerization contribute to erbB1 signaling is controversial. To examine this, we utilized two-color Quantum Dot tracking for visualization of erbB1 homodimerization and quantification of the dimer off rate (koff) on living cells. Kinetic parameters were extracted using a 3-state Hidden Markov Model to identify transition rates between free, co-confined, and dimerized states. We report that dimers composed of 2 ligand-bound receptors are long-lived and their koff is independent of kinase activity. By comparison, unliganded dimers have >4-fold faster koff. Transient co-confinement of receptors promotes repeated encounters and enhances dimer formation. Mobility decreases >6-fold when ligand-bound receptors dimerize. Blockade of erbB1 kinase activity or disruption of actin networks results in faster diffusion of receptor dimers. These results implicate both signal propagation and the cortical cytoskeleton in reduced mobility of signaling-competent erbB1 dimers.
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Affiliation(s)
- Shalini T Low-Nam
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, New Mexico, USA
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15
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Low-Nam ST, Lidke KA, Cutler PJ, Roovers RC, van Bergen PM, Henegouwen E, Wilson BS, Lidke DS. Single Quantum Dot Tracking Coupled to a Three-State HMM Provides New Mechanistic Insight Into erbB1 Homodimerization. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.1595] [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: 11/28/2022] Open
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16
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Low-Nam ST, Lidke KA, Cutler PJ, Roovers RC, van Bergen en Henegouwen PM, Wilson BS, Lidke DS. Determination of Single Molecule erbB1 Homodimer Lifetimes Using Single Quantum Dot Tracking and a Diffusive Hidden Markov Model. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.2710] [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: 10/19/2022] Open
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17
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Hilioti Z, Gallagher DA, Low-Nam ST, Ramaswamy P, Gajer P, Kingsbury TJ, Birchwood CJ, Levchenko A, Cunningham KW. GSK-3 kinases enhance calcineurin signaling by phosphorylation of RCNs. Genes Dev 2004; 18:35-47. [PMID: 14701880 PMCID: PMC314273 DOI: 10.1101/gad.1159204] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.7] [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: 10/07/2003] [Accepted: 11/18/2003] [Indexed: 11/25/2022]
Abstract
The conserved RCN family of proteins can bind and directly regulate calcineurin, a Ca(2+)-activated protein phosphatase involved in immunity, heart growth, muscle development, learning, and other processes. Whereas high levels of RCNs can inhibit calcineurin signaling in fungal and animal cells, RCNs can also stimulate calcineurin signaling when expressed at endogenous levels. Here we show that the stimulatory effect of yeast Rcn1 involves phosphorylation of a conserved serine residue by Mck1, a member of the GSK-3 family of protein kinases. Mutations at the GSK-3 consensus site of Rcn1 and human DSCR1/MCIP1 abolish the stimulatory effects on calcineurin signaling. RCNs may therefore oscillate between stimulatory and inhibitory forms in vivo in a manner similar to the Inhibitor-2 regulators of type 1 protein phosphatase. Computational modeling indicates a biphasic response of calcineurin to increasing RCN concentration such that protein phosphatase activity is stimulated by low concentrations of phospho-RCN and inhibited by high concentrations of phospho- or dephospho-RCN. This prediction was verified experimentally in yeast cells expressing Rcn1 or DSCR1/MCIP1 at different concentrations. Through the phosphorylation of RCNs, GSK-3 kinases can potentially contribute to a positive feedback loop involving calcineurin-dependent up-regulation of RCN expression. Such feedback may help explain the large induction of DSCR1/MCIP1 observed in brain of Down syndrome individuals.
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Affiliation(s)
- Zoe Hilioti
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA
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