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© The Rockefeller University Press,
0021-9525/1999//389 $5.00
The Journal of Cell Biology, Volume 147, Number 2,
, 1999 389-400
Original Article |
Integrin-Associated Protein Stimulates 
2β1-Dependent Chemotaxis via GI-Mediated Inhibition of Adenylate Cyclase and Extracellular-Regulated Kinases
frazier{at}biochem.wustl.edu
Integrin-associated protein (IAP/CD47) augments the function of
2β1 integrin in smooth muscle cells (SMC), resulting in enhanced chemotaxis toward soluble collagen (Wang, X-Q., and W.A. Frazier. 1998. Mol. Biol. Cell. 9:865). IAP-deficient SMC derived from IAP–/– animals did not migrate in response to 4N1K (KRFYVVMWKK), a peptide agonist of IAP derived from the COOH-terminal domain of thrombospondin-1 (TSP1). When normal SMC were preincubated with 4N1K or an anti-2β1 function-stimulating antibody, cell migration to soluble collagen was significantly enhanced. 4N1K-induced chemotaxis was blocked by treatment of SMC with pertussis toxin indicating that IAP acts through Gi. In agreement with this, 4N1K evoked a rapid decrease in cAMP levels which was intensified in the presence of collagen, and forskolin and 8-Br-cAMP both inhibited SMC migration stimulated via IAP. 4N1K strongly inhibited extracellular regulated kinase (ERK) activation in SMC attaching to collagen and reduced basal ERK activity in suspended SMC. Pertussis toxin treatment of SMC significantly activated ERK, suggesting that an inhibitory input was alleviated. Inhibition of ERK activity by (a) the MAP kinase kinase (MEK) inhibitor, PD98059, (b) antisense oligonucleotide depletion of ERK, and (c) expression of mitogen-activated protein (MAP) kinase phosphatase-1 in SMC all led to increased migration to collagen, 4N1K, or 4N1K plus collagen. Thus, IAP stimulates 2β1 integrin-mediated SMC migration via Gi-mediated inhibition of ERK activity and suppression of cyclic AMP levels. Both of these signaling pathways could directly modulate the state of the integrin as well as impact downstream components of the cell motility apparatus.
Key Words: integrin-associated protein • chemotaxis • MAP kinase • heterotrimeric G-proteins • cyclic AMP
© 1999 The Rockefeller University Press
1.used in this paper: 4N1K, KRFYVVMWKK; 4NGG, KRFYGGMWKK; cAMP, 3'-5' cyclic adenosine monophosphate; ECM, extracellular matrix; ERK, extracellular regulated kinase (MAP kinase p42/p44); FGF-2, fibroblast growth factor-2; IAP, integrin-associated protein or CD47; MAP, mitogen-activated protein; MEK, MAP kinase kinase; MKP-1, MAP kinase phosphatase 1; PDGF, platelet-derived growth factor; SMC, smooth muscle cells; TSP, thrombospondins (TSP1, platelet thrombospondin)
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