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Zhang Y, Dong J. Cell polarity: compassing cell division and differentiation in plants. CURRENT OPINION IN PLANT BIOLOGY 2018; 45:127-135. [PMID: 29957569 PMCID: PMC7183757 DOI: 10.1016/j.pbi.2018.06.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Revised: 06/05/2018] [Accepted: 06/12/2018] [Indexed: 05/18/2023]
Abstract
Protein polarization underlies directional cell growth, cell morphogenesis, cell division, fate specification and differentiation in plant development. Analysis of in vivo protein dynamics reveals differential mobility of polarized proteins in plant cells, which may arise from lateral diffusion, local protein-protein interactions, and is restricted by protein-membrane-cell wall connections. The asymmetric protein dynamics may provide a mechanism for the regulation of asymmetric cell division and cell differentiation. In light of recent evidence for preprophase band (PPB)-independent mechanisms for orienting division planes, polarity proteins and their dynamics might provide regulation on the PPB at the cell cortex to directly influence phragmoplast positioning or alternatively, impinge on cytoplasmic microtubule-organizing centers (MTOCs) for spindle alignment. Differentiation of specialized cell types is often associated with the spatial regulation of cell wall architecture. Here we discuss the mechanisms of polarized signaling underlying regional cell wall biosynthesis, degradation, and modification during the differentiation of root endodermal cells and leaf epidermal guard cells.
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Affiliation(s)
- Ying Zhang
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
| | - Juan Dong
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA; Department of Plant Biology, Rutgers, The State University of New Jersey, Piscataway, NJ 08901, USA.
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2
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Ghosh A, Ramagopal UA, Bonanno JB, Brenowitz M, Almo SC. Structures of the L27 Domain of Disc Large Homologue 1 Protein Illustrate a Self-Assembly Module. Biochemistry 2018; 57:1293-1305. [PMID: 29261291 DOI: 10.1021/acs.biochem.7b01074] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Disc large 1 (Dlg1) proteins, members of the MAGUK protein family, are linked to cell polarity via their participation in multiprotein assemblies. At their N-termini, Dlg1 proteins contain a L27 domain. Typically, the L27 domains participate in the formation of obligate hetero-oligomers with the L27 domains from their cognate partners. Among the MAGUKs, Dlg1 proteins exist as homo-oligomers, and the oligomerization is solely dependent on the L27 domain. Here we provide biochemical and structural evidence of homodimerization via the L27 domain of Dlg1 from Drosophila melanogaster. The structure reveals that the core of the dimer is formed by a distinctive six-helix assembly, involving all three conserved helices from each subunit (monomer). The homodimer interface is extended by the C-terminal tail of the L27 domain of Dlg1, which forms a two-stranded antiparallel β-sheet. The structure reconciles and provides a structural context for a large body of available mutational data. From our analyses, we conclude that the observed L27 homodimerization is most likely a feature unique to the Dlg1 orthologs within the MAGUK family.
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Affiliation(s)
- Agnidipta Ghosh
- Department of Biochemistry, Albert Einstein College of Medicine , Bronx, New York 10461, United States
| | - Udupi A Ramagopal
- Biological Sciences Division, Poornaprajna Institute of Scientific Research , Sadashivanagar, Bangalore 560080, India
| | - Jeffrey B Bonanno
- Department of Biochemistry, Albert Einstein College of Medicine , Bronx, New York 10461, United States
| | - Michael Brenowitz
- Department of Biochemistry, Albert Einstein College of Medicine , Bronx, New York 10461, United States
| | - Steven C Almo
- Department of Biochemistry, Albert Einstein College of Medicine , Bronx, New York 10461, United States
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Issaad N, Ait-Lounis A, Laraba-Djebari F. Cytotoxicity and actin cytoskeleton damage induced in human alveolar epithelial cells by Androctonus australis hector venom. TOXIN REV 2017. [DOI: 10.1080/15569543.2017.1320806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Nesrine Issaad
- USTHB, Faculty of Biological Sciences, Laboratory of Cellular and Molecular Biology, Bab Ezzouar, Algiers, Algeria
| | - Aouatef Ait-Lounis
- USTHB, Faculty of Biological Sciences, Laboratory of Cellular and Molecular Biology, Bab Ezzouar, Algiers, Algeria
| | - Fatima Laraba-Djebari
- USTHB, Faculty of Biological Sciences, Laboratory of Cellular and Molecular Biology, Bab Ezzouar, Algiers, Algeria
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Chung WY, Song M, Park J, Namkung W, Lee J, Kim H, Lee MG, Kim JY. Generation of ΔF508-CFTR T84 cell lines by CRISPR/Cas9-mediated genome editing. Biotechnol Lett 2016; 38:2023-2034. [DOI: 10.1007/s10529-016-2190-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2016] [Accepted: 08/18/2016] [Indexed: 12/13/2022]
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Philip R, Heiler S, Mu W, Büchler MW, Zöller M, Thuma F. Claudin-7 promotes the epithelial-mesenchymal transition in human colorectal cancer. Oncotarget 2015; 6:2046-63. [PMID: 25514462 PMCID: PMC4385835 DOI: 10.18632/oncotarget.2858] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 12/02/2014] [Indexed: 12/14/2022] Open
Abstract
In colorectal cancer (CoCa) EpCAM is frequently associated with claudin-7. There is evidence that tumor-promoting EpCAM activities are modulated by the association with claudin-7. To support this hypothesis, claudin-7 was knocked-down (kd) in HT29 and SW948 cells. HT29-cld7kd and SW948-cld7kd cells display decreased anchorage-independent growth and the capacity for holoclone-, respectively, sphere-formation is reduced. Tumor growth is delayed and cld7kd cells poorly metastasize. In line with this, migratory and invasive potential of cld7kd clones is strongly impaired, migration being inhibited by anti-CD49c, but not anti-EpCAM, although motility is reduced in EpCAM siRNA-treated cells. This is due to claudin-7 recruiting EpCAM in glycolipid-enriched membrane fractions towards claudin-7-associated TACE and presenilin2, which cleave EpCAM. The cleaved intracellular domain, EpIC, promotes epithelial-mesenchymal transition (EMT)-associated transcription factor expression, which together with fibronectin and vimentin are reduced in claudin-7kd cells. But, uptake of HT29wt and SW948wt exosomes by the claudin-7kd lines sufficed for transcription factor upregulation and for restoring motility. Thus, claudin-7 contributes to motility and invasion and is required for recruiting EpCAM towards TACE/presenilin2. EpIC generation further supports motility by promoting a shift towards EMT. Notably, EMT features of cld7-competent metastatic CoCa cells can be transferred via exosomes to poorly metastatic cells.
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Affiliation(s)
- Rahel Philip
- Department of Tumor Cell Biology, University Hospital of Surgery, Heidelberg
| | - Sarah Heiler
- Department of Tumor Cell Biology, University Hospital of Surgery, Heidelberg
| | - Wei Mu
- Department of Tumor Cell Biology, University Hospital of Surgery, Heidelberg
| | | | - Margot Zöller
- Department of Tumor Cell Biology, University Hospital of Surgery, Heidelberg
| | - Florian Thuma
- Department of Tumor Cell Biology, University Hospital of Surgery, Heidelberg
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Mruk DD, Cheng CY. The Mammalian Blood-Testis Barrier: Its Biology and Regulation. Endocr Rev 2015; 36:564-91. [PMID: 26357922 PMCID: PMC4591527 DOI: 10.1210/er.2014-1101] [Citation(s) in RCA: 358] [Impact Index Per Article: 39.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 09/03/2015] [Indexed: 12/31/2022]
Abstract
Spermatogenesis is the cellular process by which spermatogonia develop into mature spermatids within seminiferous tubules, the functional unit of the mammalian testis, under the structural and nutritional support of Sertoli cells and the precise regulation of endocrine factors. As germ cells develop, they traverse the seminiferous epithelium, a process that involves restructuring of Sertoli-germ cell junctions, as well as Sertoli-Sertoli cell junctions at the blood-testis barrier. The blood-testis barrier, one of the tightest tissue barriers in the mammalian body, divides the seminiferous epithelium into 2 compartments, basal and adluminal. The blood-testis barrier is different from most other tissue barriers in that it is not only comprised of tight junctions. Instead, tight junctions coexist and cofunction with ectoplasmic specializations, desmosomes, and gap junctions to create a unique microenvironment for the completion of meiosis and the subsequent development of spermatids into spermatozoa via spermiogenesis. Studies from the past decade or so have identified the key structural, scaffolding, and signaling proteins of the blood-testis barrier. More recent studies have defined the regulatory mechanisms that underlie blood-testis barrier function. We review here the biology and regulation of the mammalian blood-testis barrier and highlight research areas that should be expanded in future studies.
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Affiliation(s)
- Dolores D Mruk
- Center for Biomedical Research, Population Council, New York, New York 10065
| | - C Yan Cheng
- Center for Biomedical Research, Population Council, New York, New York 10065
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Fukunaga S, Kakehashi A, Sumida K, Kushida M, Asano H, Gi M, Wanibuchi H. Integrative analyses of miRNA and proteomics identify potential biological pathways associated with onset of pulmonary fibrosis in the bleomycin rat model. Toxicol Appl Pharmacol 2015; 286:188-97. [DOI: 10.1016/j.taap.2015.04.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 04/15/2015] [Accepted: 04/22/2015] [Indexed: 02/07/2023]
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Bergmann S, Steinert M. From Single Cells to Engineered and Explanted Tissues: New Perspectives in Bacterial Infection Biology. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 319:1-44. [PMID: 26404465 DOI: 10.1016/bs.ircmb.2015.06.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cell culture techniques are essential for studying host-pathogen interactions. In addition to the broad range of single cell type-based two-dimensional cell culture models, an enormous amount of coculture systems, combining two or more different cell types, has been developed. These systems enable microscopic visualization and molecular analyses of bacterial adherence and internalization mechanisms and also provide a suitable setup for various biochemical, immunological, and pharmacological applications. The implementation of natural or synthetical scaffolds elevated the model complexity to the level of three-dimensional cell culture. Additionally, several transwell-based cell culture techniques are applied to study bacterial interaction with physiological tissue barriers. For keeping highly differentiated phenotype of eukaryotic cells in ex vivo culture conditions, different kinds of microgravity-simulating rotary-wall vessel systems are employed. Furthermore, the implementation of microfluidic pumps enables constant nutrient and gas exchange during cell cultivation and allows the investigation of long-term infection processes. The highest level of cell culture complexity is reached by engineered and explanted tissues which currently pave the way for a more comprehensive view on microbial pathogenicity mechanisms.
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Affiliation(s)
- Simone Bergmann
- Institute of Microbiology, Technische Universität Braunschweig, Braunschweig, Lower Saxony, Germany
| | - Michael Steinert
- Institute of Microbiology, Technische Universität Braunschweig, Braunschweig, Lower Saxony, Germany
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Heiler S, Mu W, Zöller M, Thuma F. The importance of claudin-7 palmitoylation on membrane subdomain localization and metastasis-promoting activities. Cell Commun Signal 2015; 13:29. [PMID: 26054340 PMCID: PMC4459675 DOI: 10.1186/s12964-015-0105-y] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 04/21/2015] [Indexed: 12/14/2022] Open
Abstract
Background Claudin-7 (cld7), a tight junction (TJ) component, is also found basolaterally and in the cytoplasm. Basolaterally located cld7 is enriched in glycolipid-enriched membrane domains (GEM), where it associates with EpCAM (EpC). The conditions driving cld7 out of TJ into GEM, which is associated with a striking change in function, were not defined. Thus, we asked whether cld7 serines or palmitoylation affect cld7 location and protein, particularly EpCAM, associations. Results HEK cells were transfected with EpCAM and wild type cld7 or cld7, where serine phopsphorylation or the palmitoylation sites (AA184, AA186) (cld7mPalm) were mutated. Exchange of individual serine phosphorylation sites did not significantly affect the GEM localization and the EpCAM association. Instead, cld7mPalm was poorly recruited into GEM. This has consequences on migration and invasiveness as palmitoylated cld7 facilitates integrin and EpCAM recruitment, associates with cytoskeletal linker proteins and cooperates with MMP14, CD147 and TACE, which support motility, matrix degradation and EpCAM cleavage. On the other hand, only cld7mPalm associates with TJ proteins. Conclusion Cld7 palmitoylation prohibits TJ integration and fosters GEM recruitment. Via associated molecules, palmitoylated cld7 supports motility and invasion. Electronic supplementary material The online version of this article (doi:10.1186/s12964-015-0105-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sarah Heiler
- Department of Tumor Cell Biology, University Hospital of Surgery, Im Neuenheimer Feld 365, 69120, Heidelberg, Germany.
| | - Wei Mu
- Department of Tumor Cell Biology, University Hospital of Surgery, Im Neuenheimer Feld 365, 69120, Heidelberg, Germany.
| | - Margot Zöller
- Department of Tumor Cell Biology, University Hospital of Surgery, Im Neuenheimer Feld 365, 69120, Heidelberg, Germany.
| | - Florian Thuma
- Department of Tumor Cell Biology, University Hospital of Surgery, Im Neuenheimer Feld 365, 69120, Heidelberg, Germany.
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Frisch SM, Schaller M, Cieply B. Mechanisms that link the oncogenic epithelial-mesenchymal transition to suppression of anoikis. J Cell Sci 2013; 126:21-9. [PMID: 23516327 DOI: 10.1242/jcs.120907] [Citation(s) in RCA: 208] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The oncogenic epithelial-mesenchymal transition (EMT) contributes to tumor progression in various context-dependent ways, including increased metastatic potential, expansion of cancer stem cell subpopulations, chemo-resistance and disease recurrence. One of the hallmarks of EMT is resistance of tumor cells to anoikis. This resistance contributes to metastasis and is a defining property not only of EMT but also of cancer stem cells. Here, we review the mechanistic coupling between EMT and resistance to anoikis. The discussion focuses on several key aspects. First, we provide an update on new pathways that lead from the loss of E-cadherin to anoikis resistance. We then discuss the relevance of transcription factors that are crucial in wound healing in the context of oncogenic EMT. Next, we explore the consequences of the breakdown of cell-polarity complexes upon anoikis sensitivity, through the Hippo, Wnt and transforming growth factor β (TGF-β) pathways, emphasizing points of crossregulation. Finally, we summarize the direct regulation of cell survival genes through EMT-inducing transcription factors, and the roles of the tyrosine kinases focal adhesion kinase (FAK) and TrkB neurotrophin receptor in EMT-related regulation of anoikis. Emerging from these studies are unifying principles that will lead to improvements in cancer therapy by reprogramming sensitivity of anoikis.
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Affiliation(s)
- Steven M Frisch
- Department of Biochemistry, West Virginia University, Morgantown, WV 26506, USA.
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Thuma F, Zöller M. EpCAM-associated claudin-7 supports lymphatic spread and drug resistance in rat pancreatic cancer. Int J Cancer 2013; 133:855-66. [PMID: 23390083 DOI: 10.1002/ijc.28085] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 01/21/2013] [Indexed: 12/14/2022]
Abstract
Pancreatic cancer has a dismal prognosis because of early metastatic spread, a suggested feature of cancer-initiating cells (CIC). To control for a functional contribution of the pancreatic CIC-marker EpCAM, we explored metastasis formation by a stable EpCAM-knockdown (ASML-EpC(kd)) of the rat pancreatic adenocarcinoma line BSp73ASML (ASML(wt)). As EpCAM associates with claudin-7, an ASML-claudin-7-knockdown (ASML-cld7(kd)) was included to differentiate between EpC- and EpC-cld7-mediated effects. The metastatic capacity of ASML-EpC(kd) and more pronounced ASML-cld7(kd) cells is strikingly reduced. EpC-associated cld7 interferes with EpC-mediated cell-cell adhesion and supports migration. This requires cld7 phosphorylation and formation of an EpC-cld7-tetraspanin-alpha6beta4 complex in glycolipid-enriched membrane domains (GEM), where cld7 associates via the tetraspanin-alpha6beta4 complex with phosphorylated ezrin. The association of cld7 with alpha6beta4 and cytoskeleton strongly stimulates tumor cell migration. However, EpC does not actively contribute. Instead, GEM-located cld7 associates with presenilin-2, which facilitates EpC cleavage and thereby tumor cell proliferation. Finally, the EpC-cld7 complex promotes drug resistance. Both EpC and cld7 support MAPK and JNK activation, such that in ASML-EpC(kd) and ASML-cld7(kd) cells an undue expansion of proapoptotic molecules is observed. Only cld7 promotes activation of the PI3K/Akt pathway by a strong downregulation of Pten. Accordingly, cisplatin treatment prolongs the survival time of ASML-cld7(kd)-bearing rats. Taken together, cld7 supports tumorigenic features of EpC by provoking EpC cleavage and thereby its cotranscription factor activity. On the other hand, only cld7 is directly engaged in motility and apoptosis resistance. Thus, at least in concern of migrating CIC, it is cld7 that acts as a CIC biomarker.
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Affiliation(s)
- Florian Thuma
- Department of Tumor Cell Biology, University Hospital of Surgery, Heidelberg, Germany
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Kanasaki K, Taduri G, Koya D. Diabetic nephropathy: the role of inflammation in fibroblast activation and kidney fibrosis. Front Endocrinol (Lausanne) 2013; 4:7. [PMID: 23390421 PMCID: PMC3565176 DOI: 10.3389/fendo.2013.00007] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 01/16/2013] [Indexed: 12/13/2022] Open
Abstract
Kidney disease associated with diabetes mellitus is a major health problem worldwide. Although established therapeutic strategies, such as appropriate blood glucose control, blood pressure control with renin-angiotensin system blockade, and lipid lowering with statins, are used to treat diabetes, the contribution of diabetic end-stage kidney disease to the total number of cases requiring hemodialysis has increased tremendously in the past two decades. Once renal function starts declining, it can result in a higher frequency of renal and extra-renal events, including cardiovascular events. Therefore, slowing renal function decline is one of the main areas of focus in diabetic nephropathy research, and novel strategies are urgently needed to prevent diabetic kidney disease progression. Regardless of the type of injury and etiology, kidney fibrosis is the commonly the final outcome of progressive kidney diseases, and it results in significant destruction of normal kidney structure and accompanying functional deterioration. Kidney fibrosis is caused by prolonged injury and dysregulation of the normal wound-healing process in association with excess extracellular matrix deposition. Kidney fibroblasts play an important role in the fibrotic process, but the origin of the fibroblasts remains elusive. In addition to the activation of residential fibroblasts, other important sources of fibroblasts have been proposed, such as pericytes, fibrocytes, and fibroblasts originating from epithelial-to-mesenchymal and endothelial-to-mesenchymal transition. Inflammatory cells and cytokines play a vital role In the process of fibroblast activation. In this review, we will analyze the contribution of inflammation to the process of tissue fibrosis, the type of fibroblast activation and the therapeutic strategies targeting the inflammatory pathways in an effort to slow the progression of diabetic kidney disease.
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Affiliation(s)
- Keizo Kanasaki
- Division of Diabetology and Endocrinology, Kanazawa Medical UniversityKahoku, Japan
- *Correspondence: Keizo Kanasaki and Daisuke Koya, Division of Diabetology and Endocrinology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Kahoku Ishikawa 920-0293, Japan. e-mail: ; ; Gangadhar Taduri, Department of Nephrology, Nizam’s Institute of Medical Sciences, Punjagutta, Hyderabad 500082, Andhra Pradesh, India. e-mail:
| | - Gangadhar Taduri
- Department of Nephrology, Nizam’s Institute of Medical SciencesHyderabad, India
- *Correspondence: Keizo Kanasaki and Daisuke Koya, Division of Diabetology and Endocrinology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Kahoku Ishikawa 920-0293, Japan. e-mail: ; ; Gangadhar Taduri, Department of Nephrology, Nizam’s Institute of Medical Sciences, Punjagutta, Hyderabad 500082, Andhra Pradesh, India. e-mail:
| | - Daisuke Koya
- Division of Diabetology and Endocrinology, Kanazawa Medical UniversityKahoku, Japan
- *Correspondence: Keizo Kanasaki and Daisuke Koya, Division of Diabetology and Endocrinology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Kahoku Ishikawa 920-0293, Japan. e-mail: ; ; Gangadhar Taduri, Department of Nephrology, Nizam’s Institute of Medical Sciences, Punjagutta, Hyderabad 500082, Andhra Pradesh, India. e-mail:
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Lee K, Nelson CM. New insights into the regulation of epithelial-mesenchymal transition and tissue fibrosis. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 294:171-221. [PMID: 22364874 DOI: 10.1016/b978-0-12-394305-7.00004-5] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Tissue fibrosis often presents as the final outcome of chronic disease and is a significant cause of morbidity and mortality worldwide. Fibrosis is driven by continuous expansion of fibroblasts and myofibroblasts. Epithelial-mesenchymal transition (EMT) is a form of cell plasticity in which epithelia acquire mesenchymal phenotypes and is increasingly recognized as an integral aspect of tissue fibrogenesis. In this review, we describe recent insight into the molecular and cellular factors that regulate EMT and its underlying signaling pathways. We also consider how mechanical cues from the microenvironment affect the regulation of EMT. Finally, we discuss the role of EMT in fibrotic diseases and propose approaches for detecting and treating fibrogenesis by targeting EMT.
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Affiliation(s)
- KangAe Lee
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey, USA
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Zöller M, Jung T. The Colorectal Cancer Initiating Cell: Markers and Their Role in Liver Metastasis. ACTA ACUST UNITED AC 2011. [DOI: 10.1007/978-94-007-0292-9_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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15
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Gao N, Kaestner KH. Cdx2 regulates endo-lysosomal function and epithelial cell polarity. Genes Dev 2010; 24:1295-305. [PMID: 20551175 DOI: 10.1101/gad.1921510] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In contrast to our significant understanding of signaling cascades that determine cell polarity in lower eukaryotic or immortalized cells, little is known about the transcriptional program that governs mammalian epithelial polarization in vivo. Here we show, using conditional gene ablation and three-dimensional tissue culture, that the homeobox transcription factor Cdx2 controls apical-basolateral polarity in mouse enterocytes and human colonic epithelial cells. Cdx2 regulates a comprehensive gene network involved in endo-lysosomal maturation and protein transport. In the absence of Cdx2, defective protein trafficking impairs apical-basal transport and induces ectopic lumen formation. These defects are partially recapitulated by suppression of key apical transport components, Rab11a and Kif3b, which are regulated by Cdx2. Furthermore, Cdx2 deficiency affects components that control the organization of microvillus actin cytoskeleton, leading to severe microvillus atrophy. These results demonstrate that Cdx2 regulates epithelial cell polarity and morphogenesis through control of apical protein transport and endo-lysosomal function.
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Affiliation(s)
- Nan Gao
- Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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Ding X, Deng H, Wang D, Zhou J, Huang Y, Zhao X, Yu X, Wang M, Wang F, Ward T, Aikhionbare F, Yao X. Phospho-regulated ACAP4-Ezrin interaction is essential for histamine-stimulated parietal cell secretion. J Biol Chem 2010; 285:18769-80. [PMID: 20360010 DOI: 10.1074/jbc.m110.129007] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ezrin-radixin-moesin proteins provide a regulated linkage between membrane proteins and the cortical cytoskeleton and also participate in signal transduction pathways. Ezrin is localized to the apical membrane of parietal cells and couples the protein kinase A activation cascade to the regulated HCl secretion. Our recent proteomic study revealed a protein complex of ezrin-ACAP4-ARF6 essential for volatile membrane remodeling (Fang, Z., Miao, Y., Ding, X., Deng, H., Liu, S., Wang, F., Zhou, R., Watson, C., Fu, C., Hu, Q., Lillard, J. W., Jr., Powell, M., Chen, Y., Forte, J. G., and Yao, X. (2006) Mol. Cell Proteomics 5, 1437-1449). However, knowledge of whether ACAP4 physically interacts with ezrin and how their interaction is integrated into membrane-cytoskeletal remodeling has remained elusive. Here we provide the first evidence that ezrin interacts with ACAP4 in a protein kinase A-mediated phosphorylation-dependent manner through the N-terminal 400 amino acids of ACAP4. ACAP4 locates in the cytoplasmic membrane in resting parietal cells but translocates to the apical plasma membrane upon histamine stimulation. ACAP4 was precipitated with ezrin from secreting but not resting parietal cell lysates, suggesting a phospho-regulated interaction. Indeed, this interaction is abolished by phosphatase treatment and validated by an in vitro reconstitution assay using phospho-mimicking ezrin(S66D). Importantly, ezrin specifies the apical distribution of ACAP4 in secreting parietal cells because either suppression of ezrin or overexpression of non-phosphorylatable ezrin prevents the apical localization of ACAP4. In addition, overexpressing GTPase-activating protein-deficient ACAP4 results in an inhibition of apical membrane-cytoskeletal remodeling and gastric acid secretion. Taken together, these results define a novel molecular mechanism linking ACAP4-ezrin interaction to polarized epithelial secretion.
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Affiliation(s)
- Xia Ding
- Anhui Key Laboratory of Cellular Dynamics and Chemical Biology, University of Science and Technology of China, Hefei 230027, China
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Kalluri R. EMT: when epithelial cells decide to become mesenchymal-like cells. J Clin Invest 2009; 119:1417-9. [PMID: 19487817 DOI: 10.1172/jci39675] [Citation(s) in RCA: 697] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Epithelial-mesenchymal transition (EMT) is critical for appropriate embryonic development, and this process is re-engaged in adults during wound healing, tissue regeneration, organ fibrosis, and cancer progression. Inflammation is a crucial conspirator in the emergence of EMT in adults but is absent during embryonic development. As highlighted in this Review series, EMT is now a recognized mechanism for dispersing cells in embryos, forming fibroblasts/mesenchymal cells in injured tissues, and initiating metastasis of epithelial cancer cells. Also discussed are proposals to classify EMT into three subtypes, each of which has different functional consequences.
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Affiliation(s)
- Raghu Kalluri
- Division of Matrix Biology, Beth Israel Deaconess Medical Center, and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02215, USA.
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Abstract
The neoplastic tumour suppressors, Scribble, Dlg and Lgl, originally discovered in the vinegar fly Drosophila melanogaster, are currently being actively studied for their potential role in mammalian tumourigenesis. In Drosophila, these tumour suppressors function in a common genetic pathway to regulate apicobasal cell polarity and also play important roles in the control of cell proliferation, survival, differentiation and in cell migration/invasion. The precise mechanism by which Scribble, Dlg and Lgl function is not clear; however, they have been implicated in the regulation of signalling pathways, vesicle trafficking and in the Myosin II-actin cytoskeleton. We review the evidence for the involvement of Scribble, Dlg, and Lgl in cancer, and how the various functions ascribed to these tumour suppressors in Drosophila and mammalian systems may impact on the process of tumourigenesis.
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19
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Biber J, Hernando N, Forster I, Murer H. Regulation of phosphate transport in proximal tubules. Pflugers Arch 2008; 458:39-52. [PMID: 18758808 DOI: 10.1007/s00424-008-0580-8] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Accepted: 08/13/2008] [Indexed: 12/13/2022]
Abstract
Homeostasis of inorganic phosphate (P(i)) is primarily an affair of the kidneys. Reabsorption of the bulk of filtered P(i) occurs along the renal proximal tubule and is initiated by apically localized Na(+)-dependent P(i) cotransporters. Tubular P(i) reabsorption and therefore renal excretion of P(i) is controlled by a number of hormones, including phosphatonins, and metabolic factors. In most cases, regulation of P(i) reabsorption is achieved by changing the apical abundance of Na(+)/Pi cotransporters. The regulatory mechanisms involve various signaling pathways and a number of proteins that interact with Na(+)/P(i) cotransporters.
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Affiliation(s)
- J Biber
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Switzerland.
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20
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Desclozeaux M, Venturato J, Wylie FG, Kay JG, Joseph SR, Le HT, Stow JL. Active Rab11 and functional recycling endosome are required for E-cadherin trafficking and lumen formation during epithelial morphogenesis. Am J Physiol Cell Physiol 2008; 295:C545-56. [PMID: 18579802 DOI: 10.1152/ajpcell.00097.2008] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The correct targeting and trafficking of the adherens junction protein epithelial cadherin (E-cadherin) is a major determinant for the acquisition of epithelial cell polarity and for the maintenance of epithelial integrity. The compartments and trafficking components required to sort and transport E-cadherin to the basolateral cell surface remain to be fully defined. On the basis of previous data, we know that E-cadherin is trafficked via the recycling endosome (RE) in nonpolarized and newly polarized cells. Here we explore the role of the RE throughout epithelial morphogenesis in MDCK monolayers and cysts. Time-lapse microscopy in live cells, altering RE function biochemically, and expressing a dominant-negative form of Rab11 (DN-Rab11), each showed that the RE is always requisite for E-cadherin sorting and trafficking. The RE remained important for E-cadherin trafficking in MDCK cells from a nonpolarized state through to fully formed, polarized epithelial monolayers. During the development of epithelial cysts, DN-Rab11 disrupted E-cadherin targeting and trafficking, the subapical localization of pERM and actin, and cyst lumen formation. This final effect demonstrated an early and critical interdependence of Rab11 and the RE for E-cadherin targeting, apical membrane formation, and cell polarity in cysts.
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Affiliation(s)
- Marion Desclozeaux
- Institute for Molecular Bioscience, University of Queensland, Brisbane 4072 Queensland, Australia
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21
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Halbleib JM, Sääf AM, Brown PO, Nelson WJ. Transcriptional modulation of genes encoding structural characteristics of differentiating enterocytes during development of a polarized epithelium in vitro. Mol Biol Cell 2007; 18:4261-78. [PMID: 17699590 PMCID: PMC2043570 DOI: 10.1091/mbc.e07-04-0308] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Although there is considerable evidence implicating posttranslational mechanisms in the development of epithelial cell polarity, little is known about the patterns of gene expression and transcriptional regulation during this process. We characterized the temporal program of gene expression during cell-cell adhesion-initiated polarization of human Caco-2 cells in tissue culture, which develop structural and functional polarity similar to that of enterocytes in vivo. A distinctive switch in gene expression patterns occurred upon formation of cell-cell contacts between neighboring cells. Expression of genes involved in cell proliferation was down-regulated concomitant with induction of genes necessary for functional specialization of polarized epithelial cells. Transcriptional up-regulation of these latter genes correlated with formation of important structural and functional features in enterocyte differentiation and establishment of structural and functional cell polarity; components of the apical microvilli were induced as the brush border formed during polarization; as barrier function was established, expression of tight junction transmembrane proteins peaked; transcripts encoding components of the apical, but not the basal-lateral trafficking machinery were increased during polarization. Coordinated expression of genes encoding components of functional cell structures were often observed indicating temporal control of expression and assembly of multiprotein complexes.
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Affiliation(s)
| | | | - Patrick O. Brown
- Biochemistry, and
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305
| | - W. James Nelson
- Departments of *Molecular and Cellular Physiology
- Biological Sciences and
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22
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Abstract
Tight junctions restrict the flow of ions and aqueous molecules between cells by forming a selective barrier to the paracellular pathway. Permeability of the tight junction barrier is determined by a class of transmembrane proteins known as claudins. The relationship between claudins and paracellular permeability is complex and determined not only by the profile of claudin expression but also by the arrangement of claudins and other proteins into tight junction strands. This review summarizes progress in understanding how claudins are assembled into tight junctions and how they interact with other tight junction proteins.
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Affiliation(s)
- Michael Koval
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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23
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Jin C, Ge L, Ding X, Chen Y, Zhu H, Ward T, Wu F, Cao X, Wang Q, Yao X. PKA-mediated protein phosphorylation regulates ezrin–WWOX interaction. Biochem Biophys Res Commun 2006; 341:784-91. [PMID: 16438931 DOI: 10.1016/j.bbrc.2006.01.023] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2005] [Accepted: 01/03/2006] [Indexed: 10/25/2022]
Abstract
The ezrin-radixin-moesin proteins provide a regulated linkage between membrane proteins and the cortical cytoskeleton, and also participate in signal-transduction pathways. Ezrin is localized to the apical membrane of parietal cells and couples the cAMP-dependent protein kinase activation cascade to the regulated HCl secretion in gastric parietal cells. Our recent studies have mapped the PKA-mediated phosphorylation site to Ser(66) and established its functional role in parietal cell activation [R. Zhou et al., Characterization of protein kinase A-mediated phosphorylation of ezrin in gastric parietal cell activation, J. Biol. Chem. 278 (2003) 35651-35659], but the underlying basis for this regulation is not known. Here, we provide the first evidence that PKA-mediated phosphorylation of Ser(66)regulates the interaction of ezrin with WWOX, a WW domain-containing protein. Our biochemical study reveals that ezrin directly binds to the first WW domain of WWOX via its C-terminal tyrosine-containing polyproline sequence (470)PPPPPPVY(477). Mutational analyses further demonstrate that tyrosine(477) is essential for the ezrin-WWOX interaction. In addition, our study shows that PKA-mediated phosphorylation of ezrin is essential and sufficient for the apical localization of WWOX protein as disruption of ezrin-WWOX interaction eliminated the apical localization of WWOX. Finally, our study demonstrates the essential role of ezrin-WWOX interaction in the apical membrane remodeling associated with H,K-ATPase recruitment. Taken together, these results define a novel molecular mechanism underlying phospho-regulation of ezrin function by PKA in parietal cell activation.
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Affiliation(s)
- Changjiang Jin
- Laboratory of Cellular Dynamics, University of Science and Technology of China, Heifei National Laboratory for Physical Sciences at the Microscale, Hefei 230027, China
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24
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Affiliation(s)
- Derek C Radisky
- Mayo Clinic Cancer Center, Griffin Cancer Research Building, 4500 San Pablo Road, Jacksonville, FL 32224, USA.
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25
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Mruk DD, Lau ASN, Conway AM. Crosstalk between Rab GTPases and cell junctions. Contraception 2006; 72:280-90. [PMID: 16181972 DOI: 10.1016/j.contraception.2005.03.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2005] [Revised: 02/28/2005] [Accepted: 03/26/2005] [Indexed: 11/26/2022]
Abstract
For the past several years, studies from other laboratories, as well as ours, have begun to unravel the mechanism of germ cell movement in the testis by using several in vitro and in vivo models of tight and adherens junction assembly and disassembly, two cellular phenomena that confer cell movement. However, for cell movement to be fully appreciated, the importance of "intracellular" cell movements, such as those involving actin and microtubule filaments, must be better understood. Recent research on Rab GTPases has shown that members of this superfamily function in the trafficking of vesicles containing cargo to distinct subcellular sites such as the plasma membrane while utilizing actin and microtubule filaments as tracks. In this mini-review, we provide an overview of Rab GTPase structure, function, and regulation, while placing added emphasis on the role of Rabs in cell junction dynamics in the testis.
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Affiliation(s)
- Dolores D Mruk
- Population Council, Center for Biomedical Research 1230 York Ave., New York, NY 10021, USA.
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26
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Deora AA, Philp N, Hu J, Bok D, Rodriguez-Boulan E. Mechanisms regulating tissue-specific polarity of monocarboxylate transporters and their chaperone CD147 in kidney and retinal epithelia. Proc Natl Acad Sci U S A 2005; 102:16245-50. [PMID: 16260747 PMCID: PMC1283422 DOI: 10.1073/pnas.0504419102] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Proton-coupled monocarboxylate transporters (MCT) MCT1, MCT3, and MCT4 form heterodimeric complexes with the cell surface glycoprotein CD147 and exhibit tissue-specific polarized distributions that are essential for maintaining lactate and pH homeostasis. In the parenchymal epithelia of kidney, thyroid, and liver, MCT/CD147 heterocomplexes are localized in the basolateral membrane where they transport lactate out of or into the cell depending on metabolic conditions. A unique distribution of lactate transporters is found in the retinal pigment epithelium (RPE), which regulates lactate levels of the outer retina. In RPE, MCT1/CD147 is polarized to the apical membrane and MCT3/CD147 to the basolateral membrane. The mechanisms responsible for tissue-specific polarized distribution of MCTs are unknown. Here, we demonstrate that CD147 carries sorting information for polarized targeting of the MCT1/CD147 hetero-complexes in kidney and RPE cells. In contrast, MCT3 and MCT4 harbor dominant sorting information that cotargets CD147 to the basolateral membrane in both epithelia. RNA interference experiments show that MCT1 promotes CD147 maturation. Our results open a unique paradigm to study the molecular basis of tissue-specific polarity.
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Affiliation(s)
- Ami A Deora
- Margaret M. Dyson Vision Research Institute, Weill Medical College of Cornell University, New York, NY 10021, USA
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27
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Wang H, Guo Z, Wu F, Long F, Cao X, Liu B, Zhu Z, Yao X. PKA-mediated protein phosphorylation protects ezrin from calpain I cleavage. Biochem Biophys Res Commun 2005; 333:496-501. [PMID: 15950939 DOI: 10.1016/j.bbrc.2005.05.143] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2005] [Accepted: 05/19/2005] [Indexed: 10/25/2022]
Abstract
Ezrin is localized to the apical membrane of parietal cells and couples the cAMP-dependent protein kinase (PKA) activation cascade to the regulated HCl secretion in gastric parietal cells. Our recent studies demonstrate the functional relevance of PKA-mediated phosphorylation of ezrin in parietal cell secretion [R. Zhou, X. Cao, C. Watson, Y. Miao, Z. Guo, J.G. Forte, X. Yao, Characterization of protein kinase A-mediated phosphorylation of ezrin in gastric parietal cell activation, J. Biol. Chem. 278 (2003) 35651]. Here we show that activation of PKA protects ezrin from calpain I-mediated proteolysis without alteration of calpain I activation and fodrin breakdown. To determine whether phosphorylation of Ser66 by PKA affects the insensitivity to the calpain I-mediated cleavage, recombinant proteins of ezrin, both wild type and S66A/D mutants, were incubated with the purified calpain I. Indeed, phosphorylation-like S66D mutant ezrin is resistant to calpain I-mediated proteolysis while wild type and S66A mutant were sensitive. In fact, expression of phosphorylation-like S66D, but not S66A, mutant in parietal cells confers its resistance to calpain I-mediated proteolysis. Taken together, these results indicate that phosphorylation of ezrin by PKA modulates its sensitivity to calpain I cleavage.
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Affiliation(s)
- Hongmei Wang
- Laboratory of Cell Dynamics, University of Science and Technology of China, Hefei 230027, China
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28
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Adell T, Gamulin V, Perović-Ottstadt S, Wiens M, Korzhev M, Müller IM, Müller WEG. Evolution of metazoan cell junction proteins: the scaffold protein MAGI and the transmembrane receptor tetraspanin in the demosponge Suberites domuncula. J Mol Evol 2005; 59:41-50. [PMID: 15383906 DOI: 10.1007/s00239-004-2602-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2003] [Accepted: 01/12/2004] [Indexed: 11/26/2022]
Abstract
Until recently the positioning of the sponges (phylum Porifera) within the metazoan systematics was hampered by the lack of molecular evidence for the existence of junctional structures in the surface cell layers. In this study two genes related to the tight junctions are characterized from the demosponge Suberites domuncula: tetraspanin (SDTM4SF), a cell surface receptor, and MAGI (SDMAGI), a MAGUK (membrane-associated guanylate kinase homologue) protein. Especially the MAGI protein is known in other metazoan animal phyla to exist exclusively in tight junctions. The characteristic domains of MAGI proteins (six PDZ domains, two WW domains, and a truncated guanylate kinase motif) are conserved in the sponge protein. The functional analysis of SDMAGI done by in situ hybridization shows its expression in the surface epithelial layers (exopinacoderm and endopinacoderm). Northern blot studies reveal that expression of SDMAGI and SDTM4SF increases after formation of the pinacoderm layer in the animals as well as in primmorphs. These results support earlier notions that sponges contain junctional structures. We conclude that sponges contain epithelia whose cells are organized by cell junctions.
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Affiliation(s)
- Teresa Adell
- Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universität, Duesbergweg 6, D-55099, Mainz, Germany
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29
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Cao X, Ding X, Guo Z, Zhou R, Wang F, Long F, Wu F, Bi F, Wang Q, Fan D, Forte JG, Teng M, Yao X. PALS1 specifies the localization of ezrin to the apical membrane of gastric parietal cells. J Biol Chem 2005; 280:13584-92. [PMID: 15677456 DOI: 10.1074/jbc.m411941200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The ERM (ezrin/radixin/moesin) proteins provide a regulated linkage between membrane proteins and the cortical cytoskeleton and also participate in signal transduction pathways. Ezrin is localized to the apical membrane of parietal cells and couples the protein kinase A activation cascade to regulated HCl secretion in gastric parietal cells. Here, we show that the integrity of ezrin is essential for parietal cell activation and provide the first evidence that ezrin interacts with PALS1, an evolutionarily conserved PDZ and SH3 domain-containing protein. Our biochemical study verifies that ezrin binds to PALS1 via its N terminus and is co-localized with PALS1 to the apical membrane of gastric parietal cells. Furthermore, our study shows that PALS1 is essential for the apical localization of ezrin, as either suppression of PALS1 protein accumulation or deletion of the PALS1-binding domain of ezrin eliminated the apical localization of ezrin. Finally, our study demonstrates the essential role of ezrin-PALS1 interaction in the apical membrane remodeling associated with parietal cell secretion. Taken together, these results define a novel molecular mechanism linking ezrin to the conserved apical polarity complexes and their roles in polarized epithelial secretion of gastric parietal cells.
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Affiliation(s)
- Xinwang Cao
- School of Life Science, University of Science and Technology of China, Hefei 230027, Peoples Republic of China
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30
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Meder D, Shevchenko A, Simons K, Füllekrug J. Gp135/podocalyxin and NHERF-2 participate in the formation of a preapical domain during polarization of MDCK cells. ACTA ACUST UNITED AC 2005; 168:303-13. [PMID: 15642748 PMCID: PMC2171597 DOI: 10.1083/jcb.200407072] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Epithelial polarization involves the segregation of apical and basolateral membrane domains, which are stabilized and maintained by tight junctions and membrane traffic. We report that unlike most apical and basolateral proteins in MDCK cells, which separate only after junctions have formed, the apical marker gp135 signifies an early level of polarized membrane organization established already in single cells. We identified gp135 as the dog orthologue of podocalyxin. With a series of domain mutants we show that the COOH-terminal PSD-95/Dlg/ZO-1 (PDZ)-binding motif is targeting podocalyxin to the free surface of single cells as well as to a subdomain of the terminally polarized apical membrane. This special localization of podocalyxin is shared by the cytoplasmic PDZ-protein Na+/H+ exchanger regulatory factor (NHERF)-2. Depleting podocalyxin by RNA interference caused defects in epithelial polarization. Together, our data suggest that podocalyxin and NHERF-2 function in epithelial polarization by contributing to an early apical scaffold based on PDZ domain-mediated interactions.
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Affiliation(s)
- Doris Meder
- Max Planck Institute of Molecular Cell Biology and Genetics, D-01307 Dresden, Germany
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31
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Mruk DD, Cheng CY. Sertoli-Sertoli and Sertoli-germ cell interactions and their significance in germ cell movement in the seminiferous epithelium during spermatogenesis. Endocr Rev 2004; 25:747-806. [PMID: 15466940 DOI: 10.1210/er.2003-0022] [Citation(s) in RCA: 596] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Spermatogenesis is the process by which a single spermatogonium develops into 256 spermatozoa, one of which will fertilize the ovum. Since the 1950s when the stages of the epithelial cycle were first described, reproductive biologists have been in pursuit of one question: How can a spermatogonium traverse the epithelium, while at the same time differentiating into elongate spermatids that remain attached to the Sertoli cell throughout their development? Although it was generally agreed upon that junction restructuring was involved, at that time the types of junctions present in the testis were not even discerned. Today, it is known that tight, anchoring, and gap junctions are found in the testis. The testis also has two unique anchoring junction types, the ectoplasmic specialization and tubulobulbar complex. However, attention has recently shifted on identifying the regulatory molecules that "open" and "close" junctions, because this information will be useful in elucidating the mechanism of germ cell movement. For instance, cytokines have been shown to induce Sertoli cell tight junction disassembly by shutting down the production of tight junction proteins. Other factors such as proteases, protease inhibitors, GTPases, kinases, and phosphatases also come into play. In this review, we focus on this cellular phenomenon, recapping recent developments in the field.
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Affiliation(s)
- Dolores D Mruk
- Population Council, Center for Biomedical Research, New York, New York 10021, USA.
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32
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Boitano S, Safdar Z, Welsh DG, Bhattacharya J, Koval M. Cell-cell interactions in regulating lung function. Am J Physiol Lung Cell Mol Physiol 2004; 287:L455-9. [PMID: 15308493 DOI: 10.1152/ajplung.00172.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Tight junction barrier formation and gap junctional communication are two functions directly attributable to cell-cell contact sites. Epithelial and endothelial tight junctions are critical elements of the permeability barrier required to maintain discrete compartments in the lung. On the other hand, gap junctions enable a tissue to act as a cohesive unit by permitting metabolic coupling and enabling the direct transmission of small cytosolic signaling molecules from one cell to another. These components do not act in isolation since other junctional elements, such as adherens junctions, help regulate barrier function and gap junctional communication. Some fundamental elements related to regulation of pulmonary barrier function and gap junctional communication were presented in a Featured Topic session at the 2004 Experimental Biology Conference in Washington, DC, and are reviewed in this summary.
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Affiliation(s)
- Scott Boitano
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona 85724, USA
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33
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Kalluri R, Neilson EG. Epithelial-mesenchymal transition and its implications for fibrosis. J Clin Invest 2004. [PMID: 14679171 DOI: 10.1172/jci200320530] [Citation(s) in RCA: 1754] [Impact Index Per Article: 87.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Epithelial to mesenchymal transition (EMT) is a central mechanism for diversifying the cells found in complex tissues. This dynamic process helps organize the formation of the body plan, and while EMT is well studied in the context of embryonic development, it also plays a role in the genesis of fibroblasts during organ fibrosis in adult tissues. Emerging evidence from studies of renal fibrosis suggests that more than a third of all disease-related fibroblasts originate from tubular epithelia at the site of injury. This review highlights recent advances in the process of EMT signaling in health and disease and how it may be attenuated or reversed by selective cytokines and growth factors.
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Affiliation(s)
- Raghu Kalluri
- Center for Matrix Biology, Beth Israel Deaconess Medical Center, 330 Brookline Ave. (DANA 514), Boston, Massachusetts 02215, USA.
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34
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Kalluri R, Neilson EG. Epithelial-mesenchymal transition and its implications for fibrosis. J Clin Invest 2004; 112:1776-84. [PMID: 14679171 PMCID: PMC297008 DOI: 10.1172/jci20530] [Citation(s) in RCA: 1017] [Impact Index Per Article: 50.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Epithelial to mesenchymal transition (EMT) is a central mechanism for diversifying the cells found in complex tissues. This dynamic process helps organize the formation of the body plan, and while EMT is well studied in the context of embryonic development, it also plays a role in the genesis of fibroblasts during organ fibrosis in adult tissues. Emerging evidence from studies of renal fibrosis suggests that more than a third of all disease-related fibroblasts originate from tubular epithelia at the site of injury. This review highlights recent advances in the process of EMT signaling in health and disease and how it may be attenuated or reversed by selective cytokines and growth factors.
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Affiliation(s)
- Raghu Kalluri
- Center for Matrix Biology, Beth Israel Deaconess Medical Center, 330 Brookline Ave. (DANA 514), Boston, Massachusetts 02215, USA.
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35
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Lemmers C, Michel D, Lane-Guermonprez L, Delgrossi MH, Médina E, Arsanto JP, Le Bivic A. CRB3 binds directly to Par6 and regulates the morphogenesis of the tight junctions in mammalian epithelial cells. Mol Biol Cell 2004; 15:1324-33. [PMID: 14718572 PMCID: PMC363137 DOI: 10.1091/mbc.e03-04-0235] [Citation(s) in RCA: 231] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Crumbs is an apical transmembrane protein crucial for epithelial morphogenesis in Drosophila melanogaster embryos. A protein with all the characteristics for a Crumbs homologue has been identified from patients suffering from retinitis pigmentosa group 12, but this protein (CRB1) is only expressed in retina and some parts of the brain, both in human and mouse. Here, we describe CRB3, another Crumbs homologue that is preferentially expressed in epithelial tissues and skeletal muscles in human. CRB3 shares the conserved cytoplasmic domain with other Crumbs but exhibits a very short extracellular domain without the EGF- and laminin A-like G repeats present in the other Crumbs. CRB3 is localized to the apical and subapical area of epithelial cells from the mouse and human intestine, suggesting that it could play a role in epithelial morphogenesis. Indeed, expression of CRB3 or of a chimera containing the extracellular domain of the neurotrophin receptor p75NTR and the transmembrane and cytoplasmic domains of CRB3 led to a slower development of functional tight junctions in Madin-Darby canine kidney cells. This phenotype relied on the presence of CRB3 four last amino acids (ERLI) that are involved in a direct interaction with Par6, a regulator of epithelial polarity and tight junction formation. Thus, CRB3, through its cytoplasmic domain and its interactors, plays a role in apical membrane morphogenesis and tight junction regulation.
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Affiliation(s)
- Céline Lemmers
- Laboratoire de Neurogenèse et Morphogenèse au cours du Développement et chez l'Adulte, Unité Mixte Recherche 6156 Centre National de la Recherche Scientifique, Université de la Méditerranée, Marseille, France
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36
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Müller WEG, Wiens M, Adell T, Gamulin V, Schröder HC, Müller IM. Bauplan of Urmetazoa: Basis for Genetic Complexity of Metazoa. INTERNATIONAL REVIEW OF CYTOLOGY 2004; 235:53-92. [PMID: 15219781 DOI: 10.1016/s0074-7696(04)35002-3] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Sponges were first grouped to the animal-plants or plant-animals then to the Zoophyta or Mesozoa and finally to the Parazoa. Only after the application of molecular biological techniques was it possible to place the Porifera monophyletically with the other metazoan phyla, justifying a unification of all multicellular animals to only one kingdom, the Metazoa. The first strong support came from the discovery that cell-cell and cell-matrix adhesion molecules that were cloned from sponges and were subsequently expressed share a high DNA sequence and protein function similarity with the corresponding molecules of other metazoans. Besides these evolutionary novelties for Metazoa, sponges also have morphogens and transcription factors in common with other metazoan phyla. Surprisingly, even those elements exist in Porifera, which are characteristic for pattern and axis formation. Recent studies showed that epithelial layers of sponges are sealed against the extracellular milieu through tight-junction proteins. The cell culture system from sponges, the primmorphs, was suitable for understanding morphogenetic events. Finally, stem cell marker genes were isolated, which underscored that sponge cells have the capacity to differentiate. In the relatively short period of time, approximately 200 million years, the basic pathways had to be established that allowed the transition for multicellular organisms to a colonial system through the formation of adhesion molecules; based on the development of a complex immune system and the apoptotic machinery of an integrated system, the Urmetazoa, which evolved approximately 800 million years ago, could be reached. Hence, the Bauplan of the hypothetical Urmetazoa can now be constructed according to genomic regulatory systems similar to those found in higher Metazoa. These data caused a paradigmatic change; the Porifera are complex and simple but by far not primitive.
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Affiliation(s)
- Werner E G Müller
- Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universität, D-55099 Mainz, Germany
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37
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Abstract
During embryonic development, polarized epithelial cells are either formed during cleavage or formed from mesenchymal cells. Because the formation of epithelia during embryogenesis has to occur with high fidelity to ensure proper development, embryos allow a functional approach to study epithelial cell polarization in vivo. In particular, genetic model organisms have greatly advanced our understanding of the generation and maintenance of epithelial cell polarity. Many novel and important polarity genes have been identified and characterized in invertebrate systems, like Drosophila melanogaster and Caenorhabditis elegans. With the rapid identification of mammalian homologues of these invertebrate polarity genes, it has become clear that many important protein domains, single proteins and even entire protein complexes are evolutionarily conserved. It is to be expected that the field of epithelial cell polarity is just experiencing the 'top of the iceberg' of a large protein network that is fundamental for the specific adhesive, cell signalling and transport functions of epithelial cells.
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Affiliation(s)
- H-Arno J Müller
- Institut für Genetik, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, Düsseldorf D-40225, Germany.
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38
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Berryman MA, Goldenring JR. CLIC4 is enriched at cell-cell junctions and colocalizes with AKAP350 at the centrosome and midbody of cultured mammalian cells. ACTA ACUST UNITED AC 2003; 56:159-72. [PMID: 14569596 DOI: 10.1002/cm.10141] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
CLIC4 is a member of the chloride intracellular channel (CLIC) protein family whose principal cellular functions are poorly understood. Recently, we demonstrated that several CLIC proteins, including CLIC4, interact with AKAP350. AKAP350 is concentrated at the Golgi apparatus, centrosome, and midbody and acts as a scaffolding protein for several protein kinases and phosphatases. In this report, we show that endogenous CLIC4 and AKAP350 colocalize at the centrosome and midbody of cultured cells by immunofluorescence microscopy. Unlike AKAP350, CLIC4 is not enriched in the Golgi apparatus but is enriched in mitochondria, actin-based structures at the cell cortex, and the nuclear matrix, indicating that CLIC4-AKAP350 interactions are regulated at specific subcellular sites in vivo. In addition to the centrosome and midbody, CLIC4 colocalizes with AKAP350 and the tight junction protein ZO-1 in the apical region of polarized epithelial cells, suggesting that CLIC4 may play a role in maintaining apical-basolateral membrane polarity during mitosis and cytokinesis. Biochemical studies show that CLIC4 behaves mainly as a soluble cytosolic protein and can associate with proteins of the microtubule cytoskeleton. The localization of CLIC4 to the cortical actin cytoskeleton and its association with AKAP350 at the centrosome and midbody suggests that CLIC4 may be important for regulating cytoskeletal organization during the cell cycle. These findings lead to the conclusion that CLIC4 and possibly other CLIC proteins have alternate cellular functions that are distinct from their proposed roles as chloride channels.
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Affiliation(s)
- Mark A Berryman
- Department of Biomedical Sciences, Molecular and Cellular Biology Program, Ohio University College of Osteopathic Medicine, Athens, OH 45701, USA.
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39
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Li L, Backer J, Wong ASK, Schwanke EL, Stewart BG, Pasdar M. Bcl-2 expression decreases cadherin-mediated cell-cell adhesion. J Cell Sci 2003; 116:3687-700. [PMID: 12890751 DOI: 10.1242/jcs.00644] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Bcl-2, a member of the apoptosis-regulating family of proteins confers a survival advantage on cells by inhibiting apoptosis. Bcl-2 expression is estrogen-responsive and high in various tumors. Overexpression of Bcl-2 has been associated with the loss of contact inhibition, unregulated growth and foci formation in culture. In this study, we have examined the effects of bcl-2 overexpression and expression on cell-cell adhesion in MCF-7 and MDCK epithelial cell lines respectively. Overexpression of Bcl-2 in estrogen receptor-positive MCF-7 mammary carcinoma cells led to decreased cell surface E-cadherin and the disruption of junctional complexes concurrent with intracellular redistribution of their components. Particularly noticeable, was the partial nuclear localization of the tight junction-associated protein ZO-1 which coincided with upregulation of ErbB2. The expression of this EGF co-receptor is regulated by the ZO-1-associated transcription factor ZONAB. Growth in estrogen-depleted media led to downregulation of Bcl-2 expression and upregulation and membrane localization of all junctional proteins. Similar disruption in junctions, accompanied by decreased transepithelial resistance, was observed when Bcl-2 was expressed in MDCK cells. These results strongly suggest that Bcl-2 expression decreases the level of functional E-cadherin thereby interfering with junction formation. The inhibition of junction formation decreases cell-cell adhesion leading to the loss of contact inhibition, which, in vivo, can lead to unregulated growth and tumorigenesis.
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Affiliation(s)
- Laiji Li
- Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G2H7, Canada
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40
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Roh MH, Fan S, Liu CJ, Margolis B. The Crumbs3-Pals1 complex participates in the establishment of polarity in mammalian epithelial cells. J Cell Sci 2003; 116:2895-906. [PMID: 12771187 DOI: 10.1242/jcs.00500] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
In Drosophila, the Crumbs-Stardust-Discs-lost complex is required during the establishment of polarized epithelia. Embryos that lack a component of this complex or overexpress Crumbs exhibit defects in epithelial morphogenesis. We recently cloned a novel mammalian epithelial Crumbs isoform, Crumbs3 (CRB3). CRB3 exists in a complex at tight junctions (TJs) with Pals1 and PATJ, the mammalian homologues of Stardust and Discs lost, respectively. Here, we observe that overexpression of CRB3 leads to delayed TJ formation in MDCK epithelial cell monolayers and disruption of polarity in MDCK cysts cultured in collagen. Both phenomena require the last four residues of CRB3. Next, we expressed, in MDCK cells, a dominant-negative Myc-Lin-2-Pals1 chimeric protein, where the PDZ domain of Lin-2 was replaced with that of Pals1. TJ and apical polarity defects were also observed in these cells. Collectively, this suggests that the CRB-Pals1 interaction is important for formation of TJs and polarized epithelia. These results provide insight into the function of the mammalian Crumbs complex during TJ formation and epithelial polarization.
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Affiliation(s)
- Michael H Roh
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor 48109-0650, USA
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41
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Abstract
The kidney can be thought of as the pairing of two tubes: an epithelial tube (the nephron), carrying filtered blood and engaged in ion and water transport; and endothelial tubes (the blood vessels), delivering blood and carrying away recovered solute. The development of the nephron presents several interesting questions. How does an epithelial tube form and how is it patterned into functionally distinct components and segments? What guides the interaction between the vasculature and kidney epithelia? How are epithelial cell shape and lumen diameter maintained, and what goes wrong when kidney tubules balloon into cysts? Here, I outline the progress that has been made in answering these questions using the zebrafish pronephros as a simple, accessible model of nephron development.
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Affiliation(s)
- Iain Drummond
- Department of Medicine, Harvard Medical School and Renal Unit, Massachusetts General Hospital, 149 13th Street, Charlestown, MA 02129, USA.
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42
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Plant PJ, Fawcett JP, Lin DCC, Holdorf AD, Binns K, Kulkarni S, Pawson T. A polarity complex of mPar-6 and atypical PKC binds, phosphorylates and regulates mammalian Lgl. Nat Cell Biol 2003; 5:301-8. [PMID: 12629547 DOI: 10.1038/ncb948] [Citation(s) in RCA: 304] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2002] [Revised: 01/13/2003] [Accepted: 02/06/2003] [Indexed: 12/27/2022]
Abstract
The evolutionarily conserved proteins Par-6, atypical protein kinase C (aPKC), Cdc42 and Par-3 associate to regulate cell polarity and asymmetric cell division, but the downstream targets of this complex are largely unknown. Here we identify direct physiological interactions between mammalian aPKC, murine Par-6C (mPar-6C) and Mlgl, the mammalian orthologue of the Drosophila melanogaster tumour suppressor Lethal (2) giant larvae. In cultured cell lines and in mouse brain, aPKC, mPar-6C and Mlgl form a multiprotein complex in which Mlgl is targeted for phosphorylation on conserved serine residues. These phosphorylation sites are important for embryonic fibroblasts to polarize correctly in response to wounding and may regulate the ability of Mlgl to direct protein trafficking. Our data provide a direct physical and regulatory link between proteins of distinct polarity complexes, identify Mlgl as a functional substrate for aPKC in cell polarization and indicate that aPKC is directed to cell polarity substrates through a network of protein-protein interactions.
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Affiliation(s)
- Pamela J Plant
- Programme in Molecular Biology and Cancer, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto M5G 1X5 Canada
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43
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Takekuni K, Ikeda W, Fujito T, Morimoto K, Takeuchi M, Monden M, Takai Y. Direct binding of cell polarity protein PAR-3 to cell-cell adhesion molecule nectin at neuroepithelial cells of developing mouse. J Biol Chem 2003; 278:5497-500. [PMID: 12515806 DOI: 10.1074/jbc.c200707200] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PAR-3 is a cell polarity protein that localizes at tight junctions (TJs) by direct binding to an immunoglobulin (Ig)-like cell-cell adhesion molecule JAM-1 in mammalian epithelial cells. Another Ig-like cell-cell adhesion molecule nectin plays a role in the localization of JAM-1 at TJs in epithelial cells. Nectin furthermore plays a role in the organization of adherens junctions (AJs) and TJs. Nectin comprises a family of four members, nectin-1, -2, -3, and -4. Nectins are associated with the actin cytoskeleton through afadin, of which the PDZ domain binds to nectins through their C-terminal four amino acids. We show here that PAR-3 binds to nectin-1 and -3 in neuroepithelial cells of the embryonic telencephalon, which are equipped with AJs, but not with typical TJs. Nectin-1, -2, -3, and afadin, but not JAM-1, were concentrated at AJs in neuroepithelial cells of the embryonic telencephalon at E13.5 and PAR-3 co-localized with nectins. PAR-3 was co-immunoprecipitated with nectin-1 and -3, but not with nectin-2 or JAM-1, from the mouse whole brain at E13.5. Recombinant PAR-3 stoichiometrically bound to recombinant nectin-1 and -3. The first one of the three PDZ domains of PAR-3 bound to the C-terminal four amino acids of nectin-1 and -3. The affinities of PAR-3 and afadin for nectin-1 and -3 were similar. Cadherin-deficient L cells expressing nectin-1 and -3 formed nectin-1- and -3-based cell-cell junctions, respectively, where PAR-3 as well as afadin was recruited. These results indicate that nectin-1 and -3 are involved in the localization of PAR-3 at AJs in the neuroepithelial cells of the embryonic telencephalon.
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Affiliation(s)
- Kyoji Takekuni
- Department of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine/Faculty of Medicine, Suita 565-0871, Japan
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44
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Figueroa Y, Wald FA, Salas PJI. p34cdc2-mediated phosphorylation mobilizes microtubule-organizing centers from the apical intermediate filament scaffold in CACO-2 epithelial cells. J Biol Chem 2002; 277:37848-54. [PMID: 12151413 DOI: 10.1074/jbc.m207037200] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have shown previously that centrosomes and other microtubule-organizing centers (MTOCs) attach to the apical intermediate filament (IF) network in CACO-2 cells. In this cell line, intermediate filaments do not disorganize during mitosis. Therefore, we speculated that the trigger of the G(2)-M boundary may also detach MTOCs from their IF anchor. If that was the case, at least one of the proteins involved in the attachment must be phosphorylated by p34(cdc2) (cdk1). Using confocal microscopy and standard biochemical analysis, we found that p34(cdc2)-mediated phosphorylation indeed released MTOCs from IFs in permeabilized cells. In isolated, immunoprecipitated multiprotein complexes containing both gamma-tubulin and cytokeratin 19, p34(cdc2) phosphorylated only one protein, and phosphorylation released cytokeratin 19 from the complexes. We conclude that this as yet unidentified protein is a part of the molecular mechanism that attaches MTOCs to IFs in interphase.
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Affiliation(s)
- Yolanda Figueroa
- Department of Cell Biology and Anatomy, University of Miami School of Medicine, Miami, Florida 33101, USA
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45
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Abstract
N-type calcium (Ca2+) channels play a critical role in synaptic function, but the mechanisms responsible for their targeting in neurons are poorly understood. N-type channels are formed by an alpha(1B) (Ca(V)2.2) pore-forming subunit associated with beta and alpha2delta auxiliary subunits. By expressing epitope-tagged recombinant alpha1B subunits in rat hippocampal neuronal cultures, we demonstrate here that synaptic targeting of N-type channels depends on neuronal contacts and synapse formation. We also establish that the C-terminal 163 aa (2177-2339) of the alpha1B-1 (Ca(V)2.2a) splice variant contain sequences that are both necessary and sufficient for synaptic targeting. By site-directed mutagenesis, we demonstrate that postsynaptic density-95/discs large/zona occludens-1 and Src homology 3 domain-binding motifs located within this region of the alpha1B subunit (Maximov et al., 1999) act as synergistic synaptic targeting signals. We also show that the recombinant modular adaptor proteins Mint1 and CASK colocalize with N-type channels in synapses. We found that the alpha1B-2 (Ca(V)2.2b) splice variant is restricted to soma and dendrites and postulated that somatodendritic and axonal/presynaptic isoforms of N-type channels are generated via alternative splicing of alpha1B C termini. These data lead us to propose that during synaptogenesis, the alpha1B-1 (Ca(V)2.2a) splice variant of the N-type Ca2+ channel pore-forming subunit is recruited to presynaptic locations by means of interactions with modular adaptor proteins Mint1 and CASK. Our results provide a novel insight into the molecular mechanisms responsible for targeting of Ca2+ channels and other synaptic proteins in neurons.
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46
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Ozaita A, Martone ME, Ellisman MH, Rudy B. Differential subcellular localization of the two alternatively spliced isoforms of the Kv3.1 potassium channel subunit in brain. J Neurophysiol 2002; 88:394-408. [PMID: 12091563 DOI: 10.1152/jn.2002.88.1.394] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Voltage-gated K(+) channels containing pore-forming subunits of the Kv3 subfamily have specific roles in the fast repolarization of action potentials and enable neurons to fire repetitively at high frequencies. Each of the four known Kv3 genes encode multiple products by alternative splicing of 3' ends resulting in the expression of K(+) channel subunits differing only in their C-terminal sequence. The alternative splicing does not affect the electrophysiological properties of the channels, and its physiological role is unknown. It has been proposed that one of the functions of the alternative splicing of Kv3 genes is to produce subunit isoforms with differential subcellular membrane localizations in neurons and differential modulation by signaling pathways. We investigated the role of the alternative splicing of Kv3 subunits in subcellular localization by examining the brain distribution of the two alternatively spliced versions of the Kv3.1 gene (Kv3.1a and Kv3.1b) with antibodies specific for the alternative spliced C-termini. Kv3.1b proteins were prominently expressed in the somatic and proximal dendritic membrane of specific neuronal populations in the mouse brain. The axons of most of these neurons also expressed Kv3.1b protein. In contrast, Kv3.1a proteins were prominently expressed in the axons of some of the same neuronal populations, but there was little to no Kv3.1a protein expression in somatodendritic membrane. Exceptions to this pattern were seen in two neuronal populations with unusual targeting of axonal proteins, mitral cells of the olfactory bulb, and mesencephalic trigeminal neurons, which expressed Kv3.1a protein in dendritic and somatic membrane, respectively. The results support the hypothesis that the alternative spliced C-termini of Kv3 subunits regulate their subcellular targeting in neurons.
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Affiliation(s)
- A Ozaita
- Department of Physiology and Neuroscience and Department of Biochemistry, New York University School of Medicine, New York, New York 10016, USA
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47
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Marceau N, Loranger A, Gilbert S, Daigle N, Champetier S. Keratin-mediated resistance to stress and apoptosis in simple epithelial cells in relation to health and disease. Biochem Cell Biol 2002. [PMID: 11716296 DOI: 10.1139/o01-138] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Epithelial cells such as hepatocytes exhibit highly polarized properties as a result of the asymmetric distribution of subsets of receptors at unique portions of the surface membrane. While the proper targeting of these surface receptors and maintenance of the resulting polarity depend on microtubules (MTs), the Golgi sorting compartment, and different actin-filament networks, the contribution of keratin intermediate filaments (IFs) has been unclear. Recent data show that the latter cytoskeletal network plays a predominant role in providing resistance to various forms of stress and to apoptosis targeted to the surface membrane. In this context, we first summarize our knowledge of the domain- or assembly-related features of IF proteins and the dynamic properties of IF networks that may explain how the same keratin pair K8/K18 can exert multiple resistance-related functions in simple epithelial cells. We then examine the contribution of linker protein(s) that integrate interactions of keratin IFs with MTs and the actin-cytoskeleton network, polarity-dependent surface receptors and cytoplasmic organelles. We next address likely molecular mechanisms by which K8/K18 can selectively provide resistance to a mechanical or toxic stress, or to Fas-mediated apoptosis. Finally, these issues on keratin structure-function are examined within a context of pathological anomalies emerging in tissue architecture as a result of natural or targeted mutations, or posttranslational modifications at specific amino acid residues. Clearly. the data accumulated in recent years provide new and significant insights on the role of K8/K18, particularly under conditions where polarized cells resist to stressful or apoptotic insults.
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Affiliation(s)
- N Marceau
- Centre de recherche en cancérologie et Departement de médecine, Université Laval, Quebec, QC, Canada.
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48
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Abstract
Recently, two papers have revealed a new function for the fruit fly epithelial apical membrane protein Crumbs and its mammalian homolog CRB1 in photoreceptor cell morphogenesis. This supports the previous observation that disruption of CRB1 function can cause retinal degeneration in humans.
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Affiliation(s)
- Andrew P Kowalczyk
- Department of Dermatology, Emory University School of Medicine, Atlanta, GA 30322, USA
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49
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Jaulin-Bastard F, Arsanto JP, Le Bivic A, Navarro C, Vély F, Saito H, Marchetto S, Hatzfeld M, Santoni MJ, Birnbaum D, Borg JP. Interaction between Erbin and a Catenin-related protein in epithelial cells. J Biol Chem 2002; 277:2869-75. [PMID: 11711544 DOI: 10.1074/jbc.m109652200] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Integrity of epithelial tissues relies on the proper apical-basolateral polarity of epithelial cells. Members of the LAP (LRR and PDZ) protein family such as LET-413 and Scribble are involved in maintaining epithelial cell polarity in Caenorhabditis elegans and Drosophila melanogaster, respectively. We previously described Erbin as a mammalian LET-413 homologue interacting with ERBB2/HER2, an epidermal growth factor receptor family member. Erbin and ERBB2/HER2 are located in the basolateral membranes of epithelial cells. We show here that Erbin interacts with p0071 (also called plakophilin-4), an armadillo repeat protein linked to the cytoskeleton. Erbin binds to p0071 in vitro and in vivo in a PDZ domain-dependent manner, and both proteins colocalized in desmosomes of epithelial cells. Using a dominant negative approach, we found that integrity of epithelial cell monolayer is impaired when interaction between Erbin and p0071 is disrupted. We propose that Erbin is connected by p0071 to cytoskeletal networks in an interaction crucial for epithelial homeostasis.
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Affiliation(s)
- Fanny Jaulin-Bastard
- U119 INSERM, Molecular Oncology, Institut Paoli-Calmettes, Molecular Pharmacology, 27 boulevard Lei Roure 13009 Marseille, France
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50
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Ebnet K, Suzuki A, Horikoshi Y, Hirose T, Meyer zu Brickwedde MK, Ohno S, Vestweber D. The cell polarity protein ASIP/PAR-3 directly associates with junctional adhesion molecule (JAM). EMBO J 2001; 20:3738-48. [PMID: 11447115 PMCID: PMC125258 DOI: 10.1093/emboj/20.14.3738] [Citation(s) in RCA: 309] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The establishment and maintenance of cellular polarity are critical for the development of multicellular organisms. PAR (partitioning-defective) proteins were identified in Caenorhabditis elegans as determinants of asymmetric cell division and polarized cell growth. Recently, vertebrate orthologues of two of these proteins, ASIP/PAR-3 and PAR-6, were found to form a signalling complex with the small GTPases Cdc42/Rac1 and with atypical protein kinase C (PKC). Here we show that ASIP/PAR-3 associates with the tight-junction-associated protein junctional adhesion molecule (JAM) in vitro and in vivo. No binding was observed with claudin-1, -4 or -5. In fibroblasts and CHO cells overexpressing JAM, endogenous ASIP is recruited to JAM at sites of cell-cell contact. Over expression of truncated JAM lacking the extracellular part disrupts ASIP/PAR-3 localization at intercellular junctions and delays ASIP/PAR-3 recruitment to newly formed cell junctions. During junction formation, JAM appears early in primordial forms of junctions. Our data suggest that the ASIP/PAR-3-aPKC complex is tethered to tight junctions via its association with JAM, indicating a potential role for JAM in the generation of cell polarity in epithelial cells.
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Affiliation(s)
- Klaus Ebnet
- Institute of Cell Biology, ZMBE, University of Muenster, D-48149 Muenster, Max-Planck-Institute of Physiological and Clinical Research, D-61231 Bad Nauheim, Germany and Department of Molecular Biology, Yokohama City University School of Medicine, 3-9, Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan Corresponding authors e-mail: or K.Ebnet and A.Suzuki contributed equally to this work
| | - Atsushi Suzuki
- Institute of Cell Biology, ZMBE, University of Muenster, D-48149 Muenster, Max-Planck-Institute of Physiological and Clinical Research, D-61231 Bad Nauheim, Germany and Department of Molecular Biology, Yokohama City University School of Medicine, 3-9, Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan Corresponding authors e-mail: or K.Ebnet and A.Suzuki contributed equally to this work
| | - Yosuke Horikoshi
- Institute of Cell Biology, ZMBE, University of Muenster, D-48149 Muenster, Max-Planck-Institute of Physiological and Clinical Research, D-61231 Bad Nauheim, Germany and Department of Molecular Biology, Yokohama City University School of Medicine, 3-9, Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan Corresponding authors e-mail: or K.Ebnet and A.Suzuki contributed equally to this work
| | - Tomonori Hirose
- Institute of Cell Biology, ZMBE, University of Muenster, D-48149 Muenster, Max-Planck-Institute of Physiological and Clinical Research, D-61231 Bad Nauheim, Germany and Department of Molecular Biology, Yokohama City University School of Medicine, 3-9, Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan Corresponding authors e-mail: or K.Ebnet and A.Suzuki contributed equally to this work
| | - Maria-Katharina Meyer zu Brickwedde
- Institute of Cell Biology, ZMBE, University of Muenster, D-48149 Muenster, Max-Planck-Institute of Physiological and Clinical Research, D-61231 Bad Nauheim, Germany and Department of Molecular Biology, Yokohama City University School of Medicine, 3-9, Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan Corresponding authors e-mail: or K.Ebnet and A.Suzuki contributed equally to this work
| | - Shigeo Ohno
- Institute of Cell Biology, ZMBE, University of Muenster, D-48149 Muenster, Max-Planck-Institute of Physiological and Clinical Research, D-61231 Bad Nauheim, Germany and Department of Molecular Biology, Yokohama City University School of Medicine, 3-9, Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan Corresponding authors e-mail: or K.Ebnet and A.Suzuki contributed equally to this work
| | - Dietmar Vestweber
- Institute of Cell Biology, ZMBE, University of Muenster, D-48149 Muenster, Max-Planck-Institute of Physiological and Clinical Research, D-61231 Bad Nauheim, Germany and Department of Molecular Biology, Yokohama City University School of Medicine, 3-9, Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan Corresponding authors e-mail: or K.Ebnet and A.Suzuki contributed equally to this work
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