title: Phosphatidylinositol-4,5 bisphosphate produced by PIP5KIgamma regulates gelsolin, actin assembly, and adhesion strength of N-cadherin junctions.
abstract: Phosphoinositides regulate several actin-binding proteins but their role at intercellular adhesions has not been defined. We found that phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) was generated at sites of N-cadherin-mediated intercellular adhesion and was a critical regulator of intercellular adhesion strength. Immunostaining for PI(4,5)P2 or transfection with GFP-PH-PLCdelta showed that PI(4,5)P2 was enriched at sites of N-cadherin adhesions and this enrichment required activated Rac1. Isoform-specific immunostaining for type I phosphatidylinositol 4-phosphate 5 kinase (PIP5KI) showed that PIP5KIgamma was spatially associated with N-cadherin-Fc beads. Association of PIP5KIgamma with N-cadherin adhesions was in part dependent on the activation of RhoA. Transfection with catalytically inactive PIP5KIgamma blocked the enrichment of PI(4,5)P2 around beads. Catalytically inactive PIP5KIgamma or a cell-permeant peptide that mimics and competes for the PI(4,5)P2-binding region of the actin-binding protein gelsolin inhibited incorporation of actin monomers in response to N-cadherin ligation and reduced intercellular adhesion strength by more than twofold. Gelsolin null fibroblasts transfected with a gelsolin severing mutant containing an intact PI(4,5)P2 binding region, demonstrated intercellular adhesion strength similar to wild-type transfected controls. We conclude that PIP5KIgamma-mediated generation of PI(4,5)P2 at sites of N-cadherin contacts regulates intercellular adhesion strength, an effect due in part to PI(4,5)P2-mediated regulation of gelsolin.
authors.affiliation: Canadian Institutes of Health Research Group in Matrix Dynamics, University of Toronto, Toronto, Ontario, Canada M5S 3E2. t.elsayegh@utoronto.ca
authors.forename: T Y
authors.initials: TY
authors.lastname: El Sayegh
authors.forename: P D
authors.initials: PD
authors.lastname: Arora
authors.forename: K
authors.initials: K
authors.lastname: Ling
authors.forename: C
authors.initials: C
authors.lastname: Laschinger
authors.forename: P A
authors.initials: PA
authors.lastname: Janmey
authors.forename: R A
authors.initials: RA
authors.lastname: Anderson
authors.forename: C A
authors.initials: CA
authors.lastname: McCulloch
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D015820:Cadherins / Q000378:metabolism*; D002448:Cell Adhesion; D002645:Chickens; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000648:ultrastructure; D018260:Gelsolin / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D010455:Peptides / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D015398:Signal Transduction; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000199:Actins; D015820:Cadherins; D018260:Gelsolin; D007527:Isoenzymes; D010455:Peptides; D019269:Phosphatidylinositol 4,5-Diphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C501303:PIP5KI protein, rat; D020741:rho GTP-Binding Proteins