p38 Kinase is a negative regulator of angiotensin II signal transduction in vascular smooth muscle cells: effects on Na+/H+ exchange and ERK1/2.
Activation of the Na+/H+ exchanger isoform-1 (NHE-1) by angiotensin II is an early signal transduction event that may regulate vascular smooth muscle cell (VSMC) growth and migration. Many signal transduction events stimulated by angiotensin II are mediated by the mitogen-activated protein (MAP) kinases. To define their roles in angiotensin II-mediated NHE-1 activity, VSMCs were treated with angiotensin II and the activities of p38, c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinases 1 and 2 (ERK1/2) were measured. Angiotensin II rapidly (peak, 5 minutes) activated p38 and ERK1/2, whereas JNK was activated more slowly (peak, 30 minutes). Because angiotensin II stimulated Na+/H+ exchange within 5 minutes, the effects of p38 and ERK1/2 antagonists on Na+/H+ exchange were studied. The MEK-1 inhibitor PD98059 decreased ERK1/2 activity and Na+/H+ exchange stimulated by angiotensin II. In contrast, the specific p38 antagonist SKF-86002 increased Na+/H+ exchange. Two mechanisms were identified that may mediate the effects of p38 and SKF-86002 on angiotensin II-stimulated Na+/H+ exchange. First, angiotensin II activation of ERK1/2 was increased 1. 5- to 2.5-fold (depending on assay technique) in the presence of SKF-86002, demonstrating that p38 negatively regulates ERK1/2. Second, the ability of angiotensin II-stimulated MAP kinases to phosphorylate a glutathione S-transferase fusion protein containing amino acids 625 to 747 of NHE-1 in vitro was analyzed. The relative activities of endogenous immunoprecipitated p38, ERK1/2, and JNK were 1.0, 2.0, and 0.05 versus control, respectively suggesting that p38 and ERK1/2, but not JNK, may phosphorylate NHE-1 in VSMC. These data indicate important roles for p38 and ERK1/2 in angiotensin II-mediated regulation of the Na+/H+ exchanger in VSMC.
Department of Medicine, University of Washington, Seattle, WA, USA.
M
M
Kusuhara
E
E
Takahashi
T E
TE
Peterson
J
J
Abe
M
M
Ishida
J
J
Han
R
R
Ulevitch
B C
BC
Berk
D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006639:Histidine; D007093:Imidazoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D008297:Male; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D009131:Muscle, Smooth, Vascular / Q000737:chemistry / Q000166:cytology / Q000201:enzymology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013379:Substrate Specificity; D013844:Thiazoles / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D007093:Imidazoles; D011994:Recombinant Proteins; D017923:Sodium-Hydrogen Exchangers; D013844:Thiazoles; D000804:Angiotensin II; D006639:Histidine; C052026:6-(4-fluorophenyl)-2,3-dihydro-5-(4-pyridinyl)imidazo(2,1-b)thiazole; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D004121:Dimethyl Sulfoxide