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Hall AE, Klompstra D, Nance J. C. elegans Afadin is required for epidermal morphogenesis and functionally interfaces with the cadherin-catenin complex and RhoGAP PAC-1/ARHGAP21. Dev Biol 2024; 511:12-25. [PMID: 38556137 PMCID: PMC11088504 DOI: 10.1016/j.ydbio.2024.03.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 03/07/2024] [Accepted: 03/25/2024] [Indexed: 04/02/2024]
Abstract
During epithelial morphogenesis, the apical junctions connecting cells must remodel as cells change shape and make new connections with their neighbors. In the C. elegans embryo, new apical junctions form when epidermal cells migrate and seal with one another to encase the embryo in skin ('ventral enclosure'), and junctions remodel when epidermal cells change shape to squeeze the embryo into a worm shape ('elongation'). The junctional cadherin-catenin complex (CCC), which links epithelial cells to each other and to cortical actomyosin, is essential for C. elegans epidermal morphogenesis. RNAi genetic enhancement screens have identified several genes encoding proteins that interact with the CCC to promote epidermal morphogenesis, including the scaffolding protein Afadin (AFD-1), whose depletion alone results in only minor morphogenesis defects. Here, by creating a null mutation in afd-1, we show that afd-1 provides a significant contribution to ventral enclosure and elongation on its own. Unexpectedly, we find that afd-1 mutant phenotypes are strongly modified by diet, revealing a previously unappreciated parental nutritional input to morphogenesis. We identify functional interactions between AFD-1 and the CCC by demonstrating that E-cadherin is required for the polarized distribution of AFD-1 to cell contact sites in early embryos. Finally, we show that afd-1 promotes the enrichment of polarity regulator, and CCC-interacting protein, PAC-1/ARHGAP21 to cell contact sites, and we identify genetic interactions suggesting that afd-1 and pac-1 regulate epidermal morphogenesis at least in part through parallel mechanisms. Our findings reveal that C. elegans AFD-1 makes a significant contribution to epidermal morphogenesis and functionally interfaces with core and associated CCC proteins.
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Affiliation(s)
- Allison E Hall
- Department of Cell Biology, NYU School of Medicine, New York, NY, 10016, USA; Skirball Institute of Biomolecular Medicine, NYU School of Medicine, New York, NY, 10016, USA; Regis University, Biology Department, Denver, CO, 80221, USA.
| | - Diana Klompstra
- Department of Cell Biology, NYU School of Medicine, New York, NY, 10016, USA; Skirball Institute of Biomolecular Medicine, NYU School of Medicine, New York, NY, 10016, USA
| | - Jeremy Nance
- Department of Cell Biology, NYU School of Medicine, New York, NY, 10016, USA; Skirball Institute of Biomolecular Medicine, NYU School of Medicine, New York, NY, 10016, USA; University of Wisconsin - Madison, Department of Cell and Regenerative Biology and Center for Quantitative Cell Imaging, Madison, WI, 53706, USA.
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2
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Hall AE, Klompstra D, Nance J. C. elegans Afadin is required for epidermal morphogenesis and functionally interfaces with the cadherin-catenin complex and RhoGAP PAC-1/ARHGAP21. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.28.551013. [PMID: 37546884 PMCID: PMC10402129 DOI: 10.1101/2023.07.28.551013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
During epithelial morphogenesis, the apical junctions connecting cells must remodel as cells change shape and make new connections with their neighbors. In the C. elegans embryo, new apical junctions form when epidermal cells migrate and seal with one another to encase the embryo in skin ('ventral enclosure'), and junctions remodel when epidermal cells change shape to squeeze the embryo into a worm shape ('elongation'). The junctional cadherin-catenin complex (CCC), which links epithelial cells to each other and to cortical actomyosin, is essential for C. elegans epidermal morphogenesis. RNAi genetic enhancement screens have identified several proteins that interact with the CCC to promote epidermal morphogenesis, including the scaffolding protein Afadin (AFD-1), whose depletion alone results in only minor morphogenesis defects. Here, by creating a null mutation in afd-1 , we show that afd-1 provides a significant contribution to ventral enclosure and elongation on its own. Unexpectedly, we find that afd-1 mutant phenotypes are strongly modified by diet, revealing a previously unappreciated maternal nutritional input to morphogenesis. We identify functional interactions between AFD-1 and the CCC by demonstrating that E-cadherin is required for the polarized distribution of AFD-1 to cell contact sites in early embryos. Finally, we show that afd-1 promotes the enrichment of polarity regulator and CCC-interacting protein PAC-1/ARHGAP21 to cell contact sites, and identify genetic interactions suggesting that afd-1 and pac-1 regulate epidermal morphogenesis at least in part through parallel mechanisms. Our findings reveal that C. elegans AFD-1 makes a significant contribution to epidermal morphogenesis and functionally interfaces with core and associated CCC proteins.
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3
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Serre JM, Slabodnick MM, Goldstein B, Hardin J. SRGP-1/srGAP and AFD-1/afadin stabilize HMP-1/⍺-catenin at rosettes to seal internalization sites following gastrulation in C. elegans. PLoS Genet 2023; 19:e1010507. [PMID: 36867663 PMCID: PMC10016700 DOI: 10.1371/journal.pgen.1010507] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 03/15/2023] [Accepted: 02/13/2023] [Indexed: 03/04/2023] Open
Abstract
A hallmark of gastrulation is the establishment of germ layers by internalization of cells initially on the exterior. In C. elegans the end of gastrulation is marked by the closure of the ventral cleft, a structure formed as cells internalize during gastrulation, and the subsequent rearrangement of adjacent neuroblasts that remain on the surface. We found that a nonsense allele of srgp-1/srGAP leads to 10-15% cleft closure failure. Deletion of the SRGP-1/srGAP C-terminal domain led to a comparable rate of cleft closure failure, whereas deletion of the N-terminal F-BAR region resulted in milder defects. Loss of the SRGP-1/srGAP C-terminus or F-BAR domain results in defects in rosette formation and defective clustering of HMP-1/⍺-catenin in surface cells during cleft closure. A mutant form of HMP-1/⍺-catenin with an open M domain can suppress cleft closure defects in srgp-1 mutant backgrounds, suggesting that this mutation acts as a gain-of-function allele. Since SRGP-1 binding to HMP-1/⍺-catenin is not favored in this case, we sought another HMP-1 interactor that might be recruited when HMP-1/⍺-catenin is constitutively open. A good candidate is AFD-1/afadin, which genetically interacts with cadherin-based adhesion later during embryonic elongation. AFD-1/afadin is prominently expressed at the vertex of neuroblast rosettes in wildtype, and depletion of AFD-1/afadin increases cleft closure defects in srgp-1/srGAP and hmp-1R551/554A/⍺-catenin backgrounds. We propose that SRGP-1/srGAP promotes nascent junction formation in rosettes; as junctions mature and sustain higher levels of tension, the M domain of HMP-1/⍺-catenin opens, allowing maturing junctions to transition from recruitment of SRGP-1/srGAP to AFD-1/afadin. Our work identifies new roles for ⍺-catenin interactors during a process crucial to metazoan development.
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Affiliation(s)
- Joel M. Serre
- Program in Genetics University of Wisconsin-Madison, Wisconsin, United States of America
| | - Mark M. Slabodnick
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Department of Biology, Knox University, Galesburg, Illinois, United States of America
| | - Bob Goldstein
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Jeff Hardin
- Program in Genetics University of Wisconsin-Madison, Wisconsin, United States of America
- Department of Integrative Biology, University of Wisconsin-Madison, Wisconsin, United States of America
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4
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Rangarajan ES, Smith EW, Izard T. The nematode α-catenin ortholog, HMP1, has an extended α-helix when bound to actin filaments. J Biol Chem 2023; 299:102817. [PMID: 36539037 PMCID: PMC9860117 DOI: 10.1016/j.jbc.2022.102817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 12/09/2022] [Accepted: 12/11/2022] [Indexed: 12/23/2022] Open
Abstract
The regulation of cell-cell junctions during epidermal morphogenesis ensures tissue integrity, a process regulated by α-catenin. This cytoskeletal protein connects the cadherin complex to filamentous actin at cell-cell junctions. The cadherin-catenin complex plays key roles in cell physiology, organism development, and disease. While mutagenesis of Caenorhabditis elegans cadherin and catenin shows that these proteins are key for embryonic morphogenesis, we know surprisingly little about their structure and attachment to the cytoskeleton. In contrast to mammalian α-catenin that functions as a dimer or monomer, the α-catenin ortholog from C. elegans, HMP1 for humpback, is a monomer. Our cryogenic electron microscopy (cryoEM) structure of HMP1/α-catenin reveals that the amino- and carboxy-terminal domains of HMP1/α-catenin are disordered and not in contact with the remaining HMP1/α-catenin middle domain. Since the carboxy-terminal HMP1/α-catenin domain is the F-actin-binding domain (FABD), this interdomain constellation suggests that HMP1/α-catenin is constitutively active, which we confirm biochemically. Our perhaps most surprising finding, given the high sequence similarity between the mammalian and nematode proteins, is our cryoEM structure of HMP1/α-catenin bound to F-actin. Unlike the structure of mammalian α-catenin bound to F-actin, binding to F-actin seems to allosterically convert a loop region of the HMP1/α-catenin FABD to extend an HMP1/α-catenin FABD α-helix. We use cryoEM and bundling assays to show for the first time how the FABD of HMP1/α-catenin bundles actin in the absence of force. Collectively, our data advance our understanding of α-catenin regulation of cell-cell contacts and additionally aid our understanding of the evolution of multicellularity in metazoans.
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Affiliation(s)
| | | | - Tina Izard
- Cell Adhesion Laboratory, UF Scripps, Jupiter, Florida, USA; The Skaggs Graduate School, The Scripps Research Institute, Jupiter, Florida, USA.
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5
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Lynch AM, Zhu Y, Lucas BG, Winkelman JD, Bai K, Martin SCT, Block S, Slabodnick MM, Audhya A, Goldstein B, Pettitt J, Gardel ML, Hardin J. TES-1/Tes and ZYX-1/Zyxin protect junctional actin networks under tension during epidermal morphogenesis in the C. elegans embryo. Curr Biol 2022; 32:5189-5199.e6. [PMID: 36384139 PMCID: PMC9729467 DOI: 10.1016/j.cub.2022.10.045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 09/12/2022] [Accepted: 10/19/2022] [Indexed: 11/17/2022]
Abstract
LIM-domain-containing repeat (LCR) proteins are recruited to strained actin filaments within stress fibers in cultured cells,1,2,3 but their roles at cell-cell junctions in living organisms have not been extensively studied. Here, we show that the Caenorhabditis elegans LCR proteins TES-1/Tes and ZYX-1/Zyxin are recruited to apical junctions during embryonic elongation when junctions are under tension. In genetic backgrounds in which embryonic elongation fails, junctional recruitment is severely compromised. The two proteins display complementary patterns of expression: TES-1 is expressed in lateral (seam) epidermal cells, whereas ZYX-1 is expressed in dorsal and ventral epidermal cells. tes-1 and zyx-1 mutant embryos display junctional F-actin defects. The loss of either protein strongly enhances morphogenetic defects in hypomorphic mutant backgrounds for cadherin/catenin complex (CCC) components. The LCR regions of TES-1 and ZYX-1 are recruited to stress fiber strain sites (SFSSs) in cultured vertebrate cells. Together, these data establish TES-1 and ZYX-1 as components of a multicellular, tension-sensitive system that stabilizes the junctional actin cytoskeleton during embryonic morphogenesis.
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Affiliation(s)
- Allison M Lynch
- Program in Genetics, University of Wisconsin, Madison, WI 53706, USA
| | - Yuyun Zhu
- Program in Genetics, University of Wisconsin, Madison, WI 53706, USA
| | - Bethany G Lucas
- Department of Biology, Regis University, 3333 Regis Boulevard, Denver, CO 80221, USA
| | - Jonathan D Winkelman
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA
| | - Keliya Bai
- University of Aberdeen, Institute of Medical Sciences, Aberdeen AB25 2ZD, UK
| | | | - Samuel Block
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Mark M Slabodnick
- Department of Biology, Knox University, Galesburg, IL 61401, USA; Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Anjon Audhya
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Bob Goldstein
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jonathan Pettitt
- University of Aberdeen, Institute of Medical Sciences, Aberdeen AB25 2ZD, UK
| | - Margaret L Gardel
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA; Department of Physics, James Franck Institute and Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
| | - Jeff Hardin
- Program in Genetics, University of Wisconsin, Madison, WI 53706, USA; Biophysics Program, University of Wisconsin, Madison, WI 53706, USA; Department of Integrative Biology, University of Wisconsin, Madison, WI 53706, USA.
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6
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Serre JM, Lucas B, Martin SCT, Heier JA, Shao X, Hardin J. C. elegans srGAP is an α-catenin M domain-binding protein that strengthens cadherin-dependent adhesion during morphogenesis. Development 2022; 149:dev200775. [PMID: 36125129 PMCID: PMC10655919 DOI: 10.1242/dev.200775] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 08/23/2022] [Indexed: 11/20/2022]
Abstract
The cadherin-catenin complex (CCC) is central to embryonic development and tissue repair, yet how CCC binding partners function alongside core CCC components remains poorly understood. Here, we establish a previously unappreciated role for an evolutionarily conserved protein, the slit-robo GTPase-activating protein SRGP-1/srGAP, in cadherin-dependent morphogenetic processes in the Caenorhabditis elegans embryo. SRGP-1 binds to the M domain of the core CCC component, HMP-1/α-catenin, via its C terminus. The SRGP-1 C terminus is sufficient to target it to adherens junctions, but only during later embryonic morphogenesis, when junctional tension is known to increase. Surprisingly, mutations that disrupt stabilizing salt bridges in the M domain block this recruitment. Loss of SRGP-1 leads to an increase in mobility and decrease of junctional HMP-1. In sensitized genetic backgrounds with weakened adherens junctions, loss of SRGP-1 leads to late embryonic failure. Rescue of these phenotypes requires the C terminus of SRGP-1 but also other domains of the protein. Taken together, these data establish a role for an srGAP in stabilizing and organizing the CCC during epithelial morphogenesis by binding to a partially closed conformation of α-catenin at junctions.
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Affiliation(s)
- Joel M. Serre
- Program in Genetics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Bethany Lucas
- Department of Biology, Regis University, 3333 Regis Blvd., Denver, CO 80221, USA
| | - Sterling C. T. Martin
- Biophysics Graduate Program, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jonathon A. Heier
- Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Xiangqiang Shao
- Wisconsin State Laboratory of Hygiene, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jeff Hardin
- Program in Genetics, University of Wisconsin-Madison, Madison, WI 53706, USA
- Biophysics Graduate Program, University of Wisconsin-Madison, Madison, WI 53706, USA
- Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA
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7
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Beacham GM, Wei DT, Beyrent E, Zhang Y, Zheng J, Camacho MMK, Florens L, Hollopeter G. The Caenorhabditis elegans ASPP homolog APE-1 is a junctional protein phosphatase 1 modulator. Genetics 2022; 222:iyac102. [PMID: 35792852 PMCID: PMC9434228 DOI: 10.1093/genetics/iyac102] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 06/28/2022] [Indexed: 08/19/2023] Open
Abstract
How serine/threonine phosphatases are spatially and temporally tuned by regulatory subunits is a fundamental question in cell biology. Ankyrin repeat, SH3 domain, proline-rich-region-containing proteins are protein phosphatase 1 catalytic subunit binding partners associated with cardiocutaneous diseases. Ankyrin repeat, SH3 domain, proline-rich-region-containing proteins localize protein phosphatase 1 catalytic subunit to cell-cell junctions, but how ankyrin repeat, SH3 domain, proline-rich-region-containing proteins localize and whether they regulate protein phosphatase 1 catalytic subunit activity in vivo is unclear. Through a Caenorhabditis elegans genetic screen, we find that loss of the ankyrin repeat, SH3 domain, proline-rich-region-containing protein homolog, APE-1, suppresses a pathology called "jowls," providing us with an in vivo assay for APE-1 activity. Using immunoprecipitations and mass spectrometry, we find that APE-1 binds the protein phosphatase 1 catalytic subunit called GSP-2. Through structure-function analysis, we discover that APE-1's N-terminal half directs the APE-1-GSP-2 complex to intercellular junctions. Additionally, we isolated mutations in highly conserved residues of APE-1's ankyrin repeats that suppress jowls yet do not preclude GSP-2 binding, implying APE-1 does more than simply localize GSP-2. Indeed, in vivo reconstitution of APE-1 suggests the ankyrin repeats modulate phosphatase output, a function we find to be conserved among vertebrate homologs.
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Affiliation(s)
| | - Derek T Wei
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Erika Beyrent
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Ying Zhang
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Jian Zheng
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Mari M K Camacho
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Laurence Florens
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Gunther Hollopeter
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
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8
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Shao X, Lucas B, Strauch J, Hardin J. The adhesion modulation domain of Caenorhabditis elegans α-catenin regulates actin binding during morphogenesis. Mol Biol Cell 2019; 30:2115-2123. [PMID: 31188702 PMCID: PMC6743470 DOI: 10.1091/mbc.e19-01-0018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Maintaining tissue integrity during epidermal morphogenesis depends on α-catenin, which connects the cadherin complex to F-actin. We show that the adhesion modulation domain (AMD) of Caenorhabditis elegans HMP-1/α-catenin regulates its F-actin–binding activity and organization of junctional–proximal actin in vivo. Deleting the AMD increases F-actin binding in vitro and leads to excess actin recruitment to adherens junctions in vivo. Reducing actin binding through a compensatory mutation in the C-terminus leads to improved function. Based on the effects of phosphomimetic and nonphosphorylatable mutations, phosphorylation of S509, within the AMD, may regulate F-actin binding. Taken together, these data establish a novel role for the AMD in regulating the actin-binding ability of an α-catenin and its proper function during epithelial morphogenesis.
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Affiliation(s)
- Xiangqiang Shao
- Program in Genetics, University of Wisconsin-Madison, Madison, WI 53706
| | - Bethany Lucas
- Department of Biology, Regis University, Denver, CO 80221
| | - Jared Strauch
- Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI 53706
| | - Jeff Hardin
- Program in Genetics, University of Wisconsin-Madison, Madison, WI 53706.,Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI 53706
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9
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Shao X, Kang H, Loveless T, Lee GR, Seok C, Weis WI, Choi HJ, Hardin J. Cell-cell adhesion in metazoans relies on evolutionarily conserved features of the α-catenin·β-catenin-binding interface. J Biol Chem 2017; 292:16477-16490. [PMID: 28842483 DOI: 10.1074/jbc.m117.795567] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 07/31/2017] [Indexed: 01/26/2023] Open
Abstract
Stable tissue integrity during embryonic development relies on the function of the cadherin·catenin complex (CCC). The Caenorhabditis elegans CCC is a useful paradigm for analyzing in vivo requirements for specific interactions among the core components of the CCC, and it provides a unique opportunity to examine evolutionarily conserved mechanisms that govern the interaction between α- and β-catenin. HMP-1, unlike its mammalian homolog α-catenin, is constitutively monomeric, and its binding affinity for HMP-2/β-catenin is higher than that of α-catenin for β-catenin. A crystal structure shows that the HMP-1·HMP-2 complex forms a five-helical bundle structure distinct from the structure of the mammalian α-catenin·β-catenin complex. Deletion analysis based on the crystal structure shows that the first helix of HMP-1 is necessary for binding HMP-2 avidly in vitro and for efficient recruitment of HMP-1 to adherens junctions in embryos. HMP-2 Ser-47 and Tyr-69 flank its binding interface with HMP-1, and we show that phosphomimetic mutations at these two sites decrease binding affinity of HMP-1 to HMP-2 by 40-100-fold in vitro. In vivo experiments using HMP-2 S47E and Y69E mutants showed that they are unable to rescue hmp-2(zu364) mutants, suggesting that phosphorylation of HMP-2 on Ser-47 and Tyr-69 could be important for regulating CCC formation in C. elegans Our data provide novel insights into how cadherin-dependent cell-cell adhesion is modulated in metazoans by conserved elements as well as features unique to specific organisms.
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Affiliation(s)
| | | | - Timothy Loveless
- Department of Zoology, and.,Program in Cellular and Molecular Biology, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Gyu Rie Lee
- Chemistry, Seoul National University, Seoul 08826, South Korea, and
| | - Chaok Seok
- Chemistry, Seoul National University, Seoul 08826, South Korea, and
| | - William I Weis
- the Departments of Structural Biology and Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305
| | | | - Jeff Hardin
- From the Program in Genetics, .,Department of Zoology, and.,Program in Cellular and Molecular Biology, University of Wisconsin-Madison, Madison, Wisconsin 53706
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10
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Kang H, Bang I, Jin KS, Lee B, Lee J, Shao X, Heier JA, Kwiatkowski AV, Nelson WJ, Hardin J, Weis WI, Choi HJ. Structural and functional characterization of Caenorhabditis elegans α-catenin reveals constitutive binding to β-catenin and F-actin. J Biol Chem 2017; 292:7077-7086. [PMID: 28298447 PMCID: PMC5409474 DOI: 10.1074/jbc.m116.769778] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 03/08/2017] [Indexed: 11/06/2022] Open
Abstract
Intercellular epithelial junctions formed by classical cadherins, β-catenin, and the actin-binding protein α-catenin link the actin cytoskeletons of adjacent cells into a structural continuum. These assemblies transmit forces through the tissue and respond to intracellular and extracellular signals. However, the mechanisms of junctional assembly and regulation are poorly understood. Studies of cadherin-catenin assembly in a number of metazoans have revealed both similarities and unexpected differences in the biochemical properties of the cadherin·catenin complex that likely reflect the developmental and environmental requirements of different tissues and organisms. Here, we report the structural and biochemical characterization of HMP-1, the Caenorhabditis elegans α-catenin homolog, and compare it with mammalian α-catenin. HMP-1 shares overall similarity in structure and actin-binding properties, but displayed differences in conformational flexibility and allosteric regulation from mammalian α-catenin. HMP-1 bound filamentous actin with an affinity in the single micromolar range, even when complexed with the β-catenin homolog HMP-2 or when present in a complex of HMP-2 and the cadherin homolog HMR-1, indicating that HMP-1 binding to F-actin is not allosterically regulated by the HMP-2·HMR-1 complex. The middle (i.e. M) domain of HMP-1 appeared to be less conformationally flexible than mammalian α-catenin, which may underlie the dampened effect of HMP-2 binding on HMP-1 actin-binding activity compared with that of the mammalian homolog. In conclusion, our data indicate that HMP-1 constitutively binds β-catenin and F-actin, and although the overall structure and function of HMP-1 and related α-catenins are similar, the vertebrate proteins appear to be under more complex conformational regulation.
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Affiliation(s)
- Hyunook Kang
- From the School of Biological Sciences, Seoul National University, Seoul 08826, South Korea
| | - Injin Bang
- From the School of Biological Sciences, Seoul National University, Seoul 08826, South Korea
| | - Kyeong Sik Jin
- the Pohang Accelerator Laboratory, Pohang, Gyeongbuk 37673, South Korea
| | - Boyun Lee
- the Department of Biophysics and Chemical Biology and
| | - Junho Lee
- From the School of Biological Sciences, Seoul National University, Seoul 08826, South Korea
- the Department of Biophysics and Chemical Biology and
- the Institute of Molecular Biology and Genetics, Seoul National University, Seoul 08826, South Korea
| | - Xiangqiang Shao
- the Department of Zoology and Program in Genetics, University of Wisconsin, Madison, Wisconsin 53706
| | - Jonathon A Heier
- the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, and
| | - Adam V Kwiatkowski
- the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, and
| | - W James Nelson
- the Departments of Biology
- Molecular and Cellular Physiology, and
| | - Jeff Hardin
- the Department of Zoology and Program in Genetics, University of Wisconsin, Madison, Wisconsin 53706
| | - William I Weis
- Molecular and Cellular Physiology, and
- Structural Biology, Stanford University School of Medicine, Stanford, California 94305
| | - Hee-Jung Choi
- From the School of Biological Sciences, Seoul National University, Seoul 08826, South Korea,
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11
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12
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Abstract
The classic cadherin-catenin complex (CCC) mediates cell-cell adhesion in metazoans. Although substantial insights have been gained by studying the CCC in vertebrate tissue culture, analyzing requirements for and regulation of the CCC in vertebrates remains challenging.
Caenorhabditis elegans is a powerful system for connecting the molecular details of CCC function with functional requirements in a living organism. Recent data, using an “angstroms to embryos” approach, have elucidated functions for key residues, conserved across all metazoans, that mediate cadherin/β-catenin binding. Other recent work reveals a novel, potentially ancestral, role for the
C. elegans p120ctn homologue in regulating polarization of blastomeres in the early embryo via Cdc42 and the partitioning-defective (PAR)/atypical protein kinase C (aPKC) complex. Finally, recent work suggests that the CCC is trafficked to the cell surface via the clathrin adaptor protein complex 1 (AP-1) in surprising ways. These studies continue to underscore the value of
C. elegans as a model system for identifying conserved molecular mechanisms involving the CCC.
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Affiliation(s)
- Jeff Hardin
- Department of Zoology, University of Wisconsin-Madison, Madison, WI, USA
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