title: Mnk1 is required for angiotensin II-induced protein synthesis in vascular smooth muscle cells.
abstract: Angiotensin II (Ang II) stimulates protein synthesis in vascular smooth muscle cells (VSMCs), possibly secondary to regulatory changes at the initiation of mRNA translation. Mitogen-activated protein (MAP) kinase signal-integrating kinase-1 (Mnk1), a substrate of ERK and p38 MAP kinase, phosphorylates eukaryotic initiation factor 4E (eIF4E), an important factor in translation. The goal of the present study was to investigate the role of Mnk1 in Ang II-induced protein synthesis and to characterize the molecular mechanisms by which Mnk1 and eIF4E is activated in rat VSMCs. Ang II treatment resulted in increased Mnk1 activity and eIF4E phosphorylation. Expression of a dominant-negative Mnk1 mutant abolished Ang II-induced eIF4E phosphorylation. PD98059 or introduction of kinase-inactive MEK1/MKK1, but not SB202190 or kinase-inactive p38 MAP kinase, inhibited Ang II-induced Mnk1 activation and eIF4E phosphorylation, suggesting that ERK, but not p38 MAP kinase, is required for Ang II-induced Mnk1-eIF4E activation. Further, dominant-negative constructs for Ras, but not for Rho, Rac, or Cdc42, abolished Ang II-induced Mnk1 activation. Finally, treatment of VSMCs with CGP57380, a novel specific kinase inhibitor of Mnk1, resulted in dose-dependent decreases in Ang II-stimulated phosphorylation of eIF4E, protein synthesis, and VSMC hypertrophy. In summary, these data demonstrated that (1) Ang II-induced Mnk1 activation is mediated by the Ras-ERK cascade in VSMCs, and (2) Mnk1 is involved in Ang II-mediated protein synthesis and hypertrophy, presumably through the activation of translation-initiation. The Mnk1-eIF4E pathway may provide new insights into molecular mechanisms involved in vascular hypertrophy and other Ang II-mediated pathological states.
authors: Department of Human Genetics, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
authors: Mari
authors: M
authors: Ishida
authors: Takafumi
authors: T
authors: Ishida
authors: Hidekatsu
authors: H
authors: Nakashima
authors: Narimasa
authors: N
authors: Miho
authors: Kiyoshi
authors: K
authors: Miyagawa
authors: Kazuaki
authors: K
authors: Chayama
authors: Tetsuya
authors: T
authors: Oshima
authors: Masayuki
authors: M
authors: Kambe
authors: Masao
authors: M
authors: Yoshizumi
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology*; D000814:Aniline Compounds / Q000494:pharmacology; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D015151:Immunoblotting; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation / Q000187:drug effects; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011687:Purines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000814:Aniline Compounds; C466997:CGP 57380; D004791:Enzyme Inhibitors; D039561:Eukaryotic Initiation Factor-4E; D005419:Flavonoids; D007093:Imidazoles; D011687:Purines; D011725:Pyridines; D000804:Angiotensin II; C491394:Mknk1 protein, rat; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one