Cell volume-dependent phosphorylation of proteins of the cortical cytoskeleton and cell-cell contact sites. The role of Fyn and FER kinases.
Cell volume affects diverse functions including cytoskeletal organization, but the underlying signaling pathways remained undefined. We have shown previously that shrinkage induces Fyn-dependent tyrosine phosphorylation of the cortical actin-binding protein, cortactin. Because FER kinase was implicated in the direct phosphorylation of cortactin, we investigated the osmotic responsiveness of FER and its relationship to Fyn and cortactin. Shrinkage increased FER activity and tyrosine phosphorylation. These effects were abolished by the Src family inhibitor PP2 and strongly mitigated in Fyn-deficient but not in Src-deficient cells. FER overexpression caused cortactin phosphorylation that was further enhanced by hypertonicity. Exchange of tyrosine residues 421, 466, and 482 for phenylalanine prevented cortactin phosphorylation by hypertonicity and strongly decreased it upon FER overexpression, suggesting that FER targets primarily the same osmo-sensitive tyrosines. Because constituents of the cell-cell contacts are substrates of Fyn and FER, we investigated the effect of shrinkage on the adherens junctions. Hypertonicity provoked Fyn-dependent tyrosine phosphorylation in beta-catenin, alpha-catenin, and p120(Cas) and caused the dissociation of beta-catenin from the contacts. This process was delayed in Fyn-deficient or PP2-treated cells. Thus, FER is a volume-sensitive kinase downstream from Fyn, and the Fyn/FER pathway may contribute to the cell size-dependent reorganization of the cytoskeleton and the cell-cell contacts.
Department of Surgery, The Toronto General Hospital and University of Toronto, Toronto, Ontario M5G 1L7, Canada. akapus@transplantunit.org
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Di Ciano
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Rotstein
D022005:Adherens Junctions / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D000818:Animals; D051177:Catenins; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002460:Cell Line; D048429:Cell Size; D051356:Cortactin; D006224:Cricetinae; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism*; D004789:Enzyme Activation; D006982:Hypertonic Solutions; D007365:Intercellular Junctions / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism*; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009994:Osmolar Concentration; D009997:Osmotic Pressure; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051076:Proto-Oncogene Proteins c-fyn; D015398:Signal Transduction; D015534:Trans-Activators; D014162:Transfection; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism; D051178:alpha Catenin; D051176:beta Catenin; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D000095002:Delta Catenin
C495267:CTNNB1 protein, mouse; D051177:Catenins; D015815:Cell Adhesion Molecules; D051356:Cortactin; C495272:Ctnna1 protein, mouse; C495869:Cttn protein, mouse; D003598:Cytoskeletal Proteins; D006982:Hypertonic Solutions; D008840:Microfilament Proteins; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D051178:alpha Catenin; D051176:beta Catenin; C052602:proto-oncogene protein c-fes-fps; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; C494960:Fyn protein, mouse; D051076:Proto-Oncogene Proteins c-fyn; D019061:src-Family Kinases; D000095002:Delta Catenin