title: CD44v10 interaction with Rho-kinase (ROK) activates inositol 1,4,5-triphosphate (IP3) receptor-mediated Ca2+ signaling during hyaluronan (HA)-induced endothelial cell migration.
abstract: Aortic endothelial cells (GM7372A) express a major cell adhesion molecule, CD44v10, which binds the extracellular matrix component, hyaluronan (HA), at its external domain and interacts with various signaling molecules at its cytoplasmic domain. In this study, we have determined that CD44v10 and Rho-Kinase (ROK) are physically associated as a complex in vivo. Using a recombinant fragment of ROK (in particular, the pleckstrin homology [PH] domain) and in vitro binding assays, we have detected a specific binding interaction between the PH domain of ROK and the cytoplasmic domain of CD44. Scatchard plot analysis indicates that there is a single high-affinity CD44 binding site in the PH domain of ROK with an apparent dissociation constant (Kd) of 1.76 nM, which is comparable to CD44 binding (Kd approximately 1.56 nM) to intact ROK. These findings suggest that the PH domain is the primary ROK binding region for CD44. Furthermore, HA binding to GM7372A cells promotes RhoA-mediated ROK activity, which, in turn, increases phosphorylation of three different inositol 1, 4, 5-trisphosphate receptors (IP(3)Rs) [in particular, subtype 1 (IP(3)R1), and to a lesser extent subtype 2 (IP(3)R2) and subtype 3 (IP(3)R3)] all known as IP(3)-gated Ca(2+) channels. The phosphorylated IP(3)R1 (but not IP(3)R2 or IP(3)R3) is enhanced in its binding to IP(3) which subsequently stimulates IP(3)-mediated Ca(2+) flux. Transfection of the endothelial cells with ROK's PH cDNA significantly reduces ROK association with CD44v10, and effectively inhibits ROK-mediated phosphorylation of IP(3)Rs and IP(3)R-mediated Ca(2+) flux in vitro. The PH domain of ROK also functions as a dominant-negative mutant in vivo to block HA-dependent, CD44v10-specific intracellular Ca(2+) mobilization and endothelial cell migration. Taken together, we believe that CD44v10 interaction with ROK plays a pivotal role in IP(3)R-mediated Ca(2+) signaling during HA-mediated endothelial cell migration.
authors.affiliation: Department of Medicine, University of California San Francisco, Endocrine Unit (111N), San Francisco VA Medical Center, 94121, USA.
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Singleton
authors.forename: Lilly Y W
authors.initials: LY
authors.lastname: Bourguignon
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000187:drug effects / Q000235:genetics; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000235:genetics*; D002417:Cattle; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology*; D002465:Cell Movement / Q000187:drug effects / Q000235:genetics*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D018960:Hyaluronan Receptors / Q000378:metabolism*; D006820:Hyaluronic Acid / Q000378:metabolism / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D047908:Intracellular Signaling Peptides and Proteins; D010766:Phosphorylation; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D054460:rho-Associated Kinases
chemical_list: C117722:CD44v10 antigen; D015220:Calcium Channels; D018960:Hyaluronan Receptors; D053496:Inositol 1,4,5-Trisphosphate Receptors; D047908:Intracellular Signaling Peptides and Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D006820:Hyaluronic Acid; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases