Phenotypic modulation of arterial smooth muscle cells is associated with prolonged activation of ERK1/2.
Arterial smooth muscle cells grown in primary culture on a substrate of fibronectin in serum-free medium are converted from a contractile to a synthetic phenotype. This process is dependent on integrin signaling and includes a major structural reorganization with loss of myofilaments and formation of a large secretory apparatus. Functionally, the cells lose their contractility and become competent to migrate, secrete extracellular matrix components, and proliferate in response to growth factor stimulation. Here, it is demonstrated that the mitogen-activated protein kinases ERK1/2 play a vital role in the fibronectin-mediated modification of rat aortic smooth muscle cells. Immunoblotting showed that phosphorylated ERK1/2 (p44/p42) were expressed throughout the period when the change in phenotypic properties of the cells took place. Moreover, phosphorylated ERK1/2 accumulated in the nucleus as revealed by immunocytochemical staining. Additional support for an active role of ERK1/2 in the shift in smooth muscle phenotype was obtained by the finding that PD98059, an inhibitor of the upstream kinase MEK1, potently suppressed both the expression of phosphorylated ERK1/2 and the fine structural rebuilding of the cells. In conclusion, the observations point to an important and multifaceted role of ERK1/2 in the regulation of differentiated properties and growth of vascular smooth muscle cells.
Roy
J
J
Department of Surgical Sciences, Karolinska Hospital, S-171 76 Stockholm, Sweden. Joy.Roy@kirurgi.ki.se
Kazi
M
M
Hedin
U
U
Thyberg
J
J
D000818:Animals; D001158:Arteries / Q000166:cytology; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005353:Fibronectins / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D007797:Laminin / Q000378:metabolism; D048369:MAP Kinase Kinase 1; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009119:Muscle Contraction; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley
D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D005353:Fibronectins; D005419:Flavonoids; D007797:Laminin; D009842:Oligopeptides; C058347:glycyl-arginyl-glycyl-glutamyl-seryl-proline; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one