Tetraspanin CD9 regulates beta 1 integrin activation and enhances cell motility to fibronectin via a PI-3 kinase-dependent pathway.
Tetraspanin CD9 regulates cell motility and other adhesive processes in a variety of tissue types. Using transfected Chinese Hamster Ovary cells as our model system, we examined the cellular pathways critical for CD9 promoted cell migration. alpha 5 beta 1 integrin was directly involved as CD9 enhanced migration was abolished by the alpha 5 beta 1 blocking antibody PB1. Furthermore, the ligand mimetic peptide RGDS, significantly upregulated the expression of a beta1 ligand induced binding site (LIBS) demonstrating for the first time that CD9 expression potentiates beta1 integrin high affinity conformation states. CD9 promoted cell motility was significantly blocked by phosphatidylinositol-3 kinase (PI-3K) inhibitors, wortmannin and LY294002, whereas inhibitors targeting protein kinase C or mitogen-activated protein kinase had no effect. PI-3K dominant/negative cDNA transfections confirmed that PI-3K was an essential component. CD9 enhanced the phosphorylation of the PI-3K substrate, Akt, in response to cell adhesion on FN. CD9 expression also upregulated p130Cas phosphorylation and total protein levels; however, p130Cas siRNA knockdown did not alter the motile phenotype. CD9 enhanced migration was also unaffected by serum deprivation suggesting that growth factors were not critical. Our studies demonstrate that CD9 upregulates beta1 LIBS, and in concert with alpha 5 beta 1, enhances cell motility to FN via a PI-3K dependent mechanism.
Kotha
Jayaprakash
J
Vascular Biology Center of Excellence and the Department of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38163, USA.
Longhurst
Celia
C
Appling
Whitney
W
Jennings
Lisa K
LK
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D016466:CHO Cells; D002448:Cell Adhesion; D002465:Cell Movement; D006224:Cricetinae; D003412:Cricetulus; D050719:Crk-Associated Substrate Protein / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005353:Fibronectins / Q000378:metabolism*; D039081:Integrin alpha5beta1 / Q000378:metabolism; D019012:Integrin beta1 / Q000737:chemistry / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology; D020935:MAP Kinase Signaling System; D008562:Membrane Glycoproteins / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D060245:Tetraspanin 29
D015703:Antigens, CD; D050719:Crk-Associated Substrate Protein; D004791:Enzyme Inhibitors; D005353:Fibronectins; D039081:Integrin alpha5beta1; D019012:Integrin beta1; D036341:Intercellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D060245:Tetraspanin 29