Ectopic expression of human and feline CD9 in a human B cell line confers beta 1 integrin-dependent motility on fibronectin and laminin substrates and enhanced tyrosine phosphorylation.
Few molecules have been shown to confer cell motility. Although the motility-arresting properties of anti-CD9 monoclonal antibody (mAb) suggest the transmembrane 4 superfamily (TM4SF) member CD9 can induce a motorgenic signal, gene transfection studies have failed to confirm this hypothesis. We report here that ectopic expression of human CD9 (CD9h) and feline CD9 (CD9f) in the CD9-negative, poorly motile, human B cell line Raji dramatically enhances migration across fibronectin- and laminin-coated polycarbonate filters. Migration of Raji/CD9h and Raji/CD9f on either substrate was inhibited by the anti-CD9 mAb 50H.19 and by the anti-beta 1 integrin mAb AP-138. Migration of Raji/CD9h on laminin was potently inhibited by the anti-VLA-6 integrin mAb GoH3 and by the anti-VLA-4 integrin mAb 44H6, whereas migration of Raji/CD9h on fibronectin was inhibited only by mAb 44H6. Since CD9h-transfected Raji cells adhered to fibronectin as effectively as mock transfectants, expression of CD9 enhanced motility, but not adhesion. CD9-enhanced migration was inhibited by the protein tyrosine kinase inhibitor herbimycin A suggesting that tyrosine phosphorylation played a role in the generation of a motorgenic signal. Raji/CD9h transfectants adherent to fibronectin expressed 6-fold higher levels of phosphotyrosine than Raji. Raji/CD9f transfectants also phosphorylated proteins on tyrosine more effectively than Raji including a protein of 110 kDa which was phosphorylated on the motility-inducing substrates laminin and fibronectin, but not on bovine serum albumin. Our results support a role for CD9 in the amplification of a motorgenic signal in B cells involving beta 1 integrins and the activation of protein tyrosine kinases.
Shaw
A R
AR
Department of Oncology, University of Alberta, Edmonton, Canada.
Domanska
A
A
Mak
A
A
Gilchrist
A
A
Dobler
K
K
Visser
L
L
Poppema
S
S
Fliegel
L
L
Letarte
M
M
Willett
B J
BJ
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015703:Antigens, CD / Q000096:biosynthesis / Q000502:physiology*; D001402:B-Lymphocytes / Q000276:immunology*; D016227:Benzoquinones; D002415:Cats; D002417:Cattle; D002460:Cell Line; D002465:Cell Movement; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005353:Fibronectins; D005434:Flow Cytometry; D015870:Gene Expression; D006801:Humans; D019012:Integrin beta1 / Q000502:physiology; D047029:Lactams, Macrocyclic; D007797:Laminin; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000502:physiology; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011809:Quinones / Q000494:pharmacology; D011994:Recombinant Proteins; D017828:Rifabutin / Q000031:analogs & derivatives; D012710:Serum Albumin, Bovine; D015398:Signal Transduction; D060245:Tetraspanin 29; D014162:Transfection
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D016227:Benzoquinones; C554869:CD9 protein, human; D004791:Enzyme Inhibitors; D005353:Fibronectins; D019012:Integrin beta1; D047029:Lactams, Macrocyclic; D007797:Laminin; D008562:Membrane Glycoproteins; D011809:Quinones; D011994:Recombinant Proteins; D060245:Tetraspanin 29; D017828:Rifabutin; D019000:Phosphotyrosine; D012710:Serum Albumin, Bovine; C020754:herbimycin; D011505:Protein-Tyrosine Kinases