Background:
Integrins are major adhesion receptors that not only regulate cytoskeletal organization, but also trigger a variety of intracellular signal transduction pathways. we examined the effects of increased extracellular matrix (ecm) accumulation on monocyte chemoattractant protein-1 (mcp-1) expression, which is known to play an important role in the progression of various glomerular diseases.
Methods:
Mcp-1 mrna and protein expression in cultured rat mesangial cells (mc) attached to ecm proteins were examined by reverse transcription (rt)-polymerase chain reaction (pcr) and western blotting, respectively. phosphorylation of focal adhesion kinase (fak) was measured by western blotting. effects of wild-type and dominant-negative fak on mcp-1 expression were examined by a transient transfection assay.
Results:
Cell adhesion to fibronectin-induced phosphorylation of fak and mcp-1 mrna expression in time- and dose-dependent manners followed by increased mcp-1 protein expression. all integrin-interacting substrates (laminin and types i, iii, and iv collagens) also increased levels of fak phosphorylation and mcp-1 expression, whereas nonspecific adhesive substrates (polylysine and concanavalin a) had no significant effects. overexpression of wild-type fak increased phosphorylation of fak and expression of mcp-1 mrna and protein, whereas transfection of dominant-negative fak abolished adhesion-induced mcp-1 expression. adhesion-induced expression of mcp-1 mrna was inhibited by genistein and tosyl phenylalanyl chloromethylketone (tpck), suggesting that tyrosine kinases [e.g., fak, and nuclear factor kappa b (nf-kappa b)] are necessary in this signaling.
Conclusion:
Our results indicate that integrin-mediated cell adhesion to the ecm can induce mcp-1 expression through activation of fak, and suggest a role for altered ecm deposition in the progression of glomerular diseases by affecting gene expression.