LDL-activated p38 in endothelial cells is mediated by Ras.
Endothelial dysfunction is a major atherogenic proinflammatory event. LDL causes the activation and phenotypic changes of cultured vascular endothelial cells (ECs). We previously reported that LDL activates c-Jun and AP-1 in ECs. In this study, we demonstrated that p38-ATF-2 is activated by LDL in human ECs and that this activation is mediated by Ras. When ECs are incubated with LDL in pathophysiological concentrations, the p38-mediated ATF-2 phosphorylation and ATF-2 transactivation are increased in a time- and dose-dependent manner. To elucidate the upstream mechanism in LDL-activated p38 in ECs, we demonstrate that LDL increases Ras translocation from the cytoplasm to the cellular membrane, with concurrent increases in Ras binding activity to GST-Raf-1. Overexpression of RasN17, a dominant negative mutant of Ras, attenuates the LDL-induced increases in (1) phosphorylation of ATF-2, (2) phosphorylation of c-Jun, (3) AP-1 binding, and (4) AP-1-driven luciferase activity. To study the effect of p38 in the regulation of an LDL targeting gene, we show that a specific p38 inhibitor attenuates LDL-induced E-selectin at the mRNA level. Thus, LDL activates both p38 and JNK signaling pathways through Ras activation, and furthermore, these events may play an important role in LDL-induced endothelial activation.
Zhu
Y
Y
Division of Biomedical Sciences, University of California, Riverside, CA 92521, USA. yi.zhu@ucr.edu
Liao
H
H
Wang
N
N
Ma
K S
KS
Verna
L K
LK
Shyy
J Y
JY
Chien
S
S
Stemerman
M B
MB
D051698:Activating Transcription Factor 2; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D019040:E-Selectin / Q000096:biosynthesis / Q000235:genetics; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009154:Mutation; D021381:Protein Transport; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D015534:Trans-Activators / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; D017362:Cyclic AMP Response Element-Binding Protein; D019040:E-Selectin; D004791:Enzyme Inhibitors; D007093:Imidazoles; D008077:Lipoproteins, LDL; D016755:Proto-Oncogene Proteins c-jun; D011725:Pyridines; D012333:RNA, Messenger; D015534:Trans-Activators; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); C093642:SB 203580