Integrins induce expression of monocyte chemoattractant protein-1 via focal adhesion kinase in mesangial cells.
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.


CONCLUSIONS
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.
Watanabe
Yujiro
Y
Second Department of Internal Medicine, University of Occupational and Environmental Health, School of Medicine, Yahatanishi, Kitakyushu, Japan.
Tamura
Masahito
M
Osajima
Akihiko
A
Anai
Hirofumi
H
Kabashima
Narutoshi
N
Serino
Ryota
R
Nakashima
Yasuhide
Y
D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000037:antagonists & inhibitors / Q000235:genetics*; D005109:Extracellular Matrix / Q000378:metabolism; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D015870:Gene Expression / Q000502:physiology; D005920:Glomerular Mesangium / Q000166:cytology / Q000502:physiology*; D016023:Integrins / Q000378:metabolism*; D008297:Male; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000494:pharmacology
D018932:Chemokine CCL2; D016023:Integrins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D014108:Tosylphenylalanyl Chloromethyl Ketone; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496052:Ptk2 protein, rat