PDGF-BB enhances monocyte chemoattractant protein-1 mRNA stability in smooth muscle cells by downregulating ribonuclease activity.
Platelet-derived growth factor (PDGF) has protean manifestations, including the regulation of growth and migration, in many cell types. We have previously reported that PDGF-BB induces the accumulation of monocyte chemoattractant protein (MCP)-1 mRNA in smooth muscle cells (SMC), in large part due to an increase in mRNA stability. To elucidate the mechanism by which PDGF-BB stabilizes MCP-1 mRNA, we have employed in vitro RNA gel mobility shift and decay assays. Cytoplasmic extracts from PDGF-BB-treated SMC increased the half-life of in vitro transcribed MCP-1 mRNA from approximately 45 min to >2 h. PDGF-BB-inhibitable degradation was not dependent on specific regions of the MCP-1 mRNA and was equally effective on a variety of in vitro transcribed mRNAs. Angiotensin II had a similar effect on MCP-1 mRNA stability, whereas tumor necrosis factor-alpha and basic fibroblast growth factor did not. The PDGF-BB-inhibitable RNAse activity was active at pH 6.6 and heat stable, but was sensitive to proteinase K. Extracts from PDGF-BB- or angiotensin II-treated cells inhibited the RNAse activity of control extracts, suggesting that the effect of PDGF-BB and angiotensin II are due to activation of a soluble inhibitor of the RNAse. The effect of PDGF-BB was blocked by inhibitors of tyrosine phosphorylation, but not by inhibitors of phosphatidylinositol 3-kinase or mitogen-activated protein kinases. These studies provide new insights into the mechanisms by which PDGF-BB enhances mRNA accumulation.
Liu
Bin
B
Department of Medicine, University of Rochester, Box 679, 601 Elmwood Avenue, Rochester, NY 14642, USA.
Poon
Michael
M
Taubman
Mark B
MB
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D000077214:Becaplermin; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000187:drug effects / Q000235:genetics*; D058544:Class Ib Phosphatidylinositol 3-Kinase; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006207:Half-Life; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000378:metabolism / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D020574:Proto-Oncogene Proteins c-sis; D020871:RNA Stability / Q000187:drug effects*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism; D012260:Ribonucleases / Q000187:drug effects / Q000378:metabolism*; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
D018932:Chemokine CCL2; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D000804:Angiotensin II; D000077214:Becaplermin; D019869:Phosphatidylinositol 3-Kinases; D058544:Class Ib Phosphatidylinositol 3-Kinase; C099852:PDGF receptor tyrosine kinase; D017479:Receptors, Platelet-Derived Growth Factor; D019061:src-Family Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D012260:Ribonucleases