A potential role for extracellular signal-regulated kinases in prostaglandin F2alpha-induced protein synthesis in smooth muscle cells.
To understand the mechanisms of prostaglandin F2alpha (PGF2alpha)-induced protein synthesis in vascular smooth muscle cells (VSMC), we have studied its effect on two major signal transduction pathways: mitogen-activated protein kinases and phosphatidylinositol 3-kinase (PI3-kinase) and their downstream targets ribosomal protein S6 kinase (p70(S6k)) and eukaryotic initiation factor eIF4E and its regulator 4E-BP1. PGF2alpha induced the activities of extracellular signal-regulated kinase 2 (ERK2) and Jun N-terminal kinase 1 (JNK1) groups of mitogen-activated protein kinases, PI3-kinase, and p70(S6k) in a time-dependent manner in growth-arrested VSMC. PGF2alpha also induced eIF4E and 4E-BP1 phosphorylation, global protein synthesis, and basic fibroblast growth factor-2 (bFGF-2) expression in VSMC. Whereas inhibition of PI3-kinase by wortmannin completely blocked the p70(S6k) activation, it only partially decreased the ERK2 activity, and had no significant effect on global protein synthesis and bFGF-2 expression induced by PGF2alpha. Rapamycin, a potent inhibitor of p70(S6k), also failed to prevent PGF2alpha-induced global protein synthesis and bFGF-2 expression, although it partially decreased ERK2 activity. In contrast, inhibition of ERK2 activity by PD 098059 led to a significant loss of PGF2alpha-induced eIF4E and 4E-BP1 phosphorylation, global protein synthesis, and bFGF-2 expression. PGF2alpha-induced phosphorylation of eIF4E and 4E-BP1 was also found to be sensitive to inhibition by both wortmannin and rapamycin. These findings demonstrate that 1) PI3-kinase-dependent and independent mechanisms appear to be involved in PGF2alpha-induced activation of ERK2; 2) PGF2alpha-induced eIF4E and 4E-BP1 phosphorylation appear to be mediated by both ERK-dependent and PI3-kinase-dependent rapamycin-sensitive mechanisms; and 3) ERK-dependent eIF4E phosphorylation but not PI3-kinase-dependent p70(S6k) activation correlates with PGF2alpha-induced global protein synthesis and bFGF-2 expression in VSMC.
Rao
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GN
Division of Cardiology, University of Texas Medical Branch, Galveston, Texas 77555, USA. grao@utmb.edu
Madamanchi
N R
NR
Lele
M
M
Gadiparthi
L
L
Gingras
A C
AC
Eling
T E
TE
Sonenberg
N
N
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002352:Carrier Proteins; D002478:Cells, Cultured; D015237:Dinoprost / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D039561:Eukaryotic Initiation Factor-4E; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D009130:Muscle, Smooth / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D010448:Peptide Initiation Factors / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D015398:Signal Transduction; D000077191:Wortmannin
D000730:Androstadienes; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002352:Carrier Proteins; D015237:Dinoprost; D004791:Enzyme Inhibitors; D039561:Eukaryotic Initiation Factor-4E; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D010448:Peptide Initiation Factors; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins; D019893:Ribosomal Protein S6 Kinases; D000077191:Wortmannin; C499526:Eif4ebp1 protein, rat