Activation of protein synthesis in cardiomyocytes by the hypertrophic agent phenylephrine requires the activation of ERK and involves phosphorylation of tuberous sclerosis complex 2 (TSC2)
- 7 June 2005
- journal article
- Published by Portland Press Ltd. in Biochemical Journal
- Vol. 388 (3), 973-984
- https://doi.org/10.1042/bj20041888
Abstract
The hypertrophic Gq-protein-coupled receptor agonist PE (phenylephrine) activates protein synthesis. We showed previously that activation of protein synthesis by PE requires MEK [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase] and mTOR (mammalian target of rapamycin). However, it remained unclear whether ERK activation was required and which downstream components were involved in activating mTOR and protein synthesis. Using an adenovirus encoding the MKP3 (MAPK phosphatase 3) to inhibit ERK activity, we demonstrate that ERK is essential for the activation of protein synthesis by PE. Activation and phosphorylation of S6K1 (ribosomal protein S6 kinase 1) and phosphorylation of eIF4E (eukaryotic initiation factor 4E)-binding protein (both are mTOR targets) were also inhibited by MKP3, suggesting that ERK is also required for the activation of mTOR signalling. PE stimulation of cardiomyocytes induced the phosphorylation of TSC2 (tuberous sclerosis complex 2), a negative regulator of mTOR activity. TSC2 was phosphorylated only weakly at Thr1462, but phosphorylated at additional sites within the sequence RXRXX(S/T). This differs from the phosphorylation induced by insulin, indicating that MEK/ERK signalling targets distinct sites in TSC2. This phosphorylation may be mediated by p90RSK (90 kDa ribosomal protein S6K), which is activated by ERK, and appears to involve phosphorylation at Ser1798. Activation of protein synthesis by PE is partially insensitive to the mTOR inhibitor rapamycin. Inhibition of the MAPK-interacting kinases by CGP57380 decreases the phosphorylation of eIF4E and PE-induced protein synthesis. Moreover, CGP57380+rapamycin inhibited protein synthesis to the same extent as blocking ERK activation, suggesting that MAPK-interacting kinases and regulation of mTOR each contribute to the activation of protein synthesis by PE in cardiomyocytes.Keywords
This publication has 61 references indexed in Scilit:
- Inactivation of the Tuberous Sclerosis Complex-1 and -2 Gene Products Occurs by Phosphoinositide 3-Kinase/Akt-dependent and -independent Phosphorylation of TuberinPublished by Elsevier BV ,2003
- United at last: the tuberous sclerosis complex gene products connect the phosphoinositide 3-kinase/Akt pathway to mammalian target of rapamycin (mTOR) signallingBiochemical Society Transactions, 2003
- Rapamycin Attenuates Load-Induced Cardiac Hypertrophy in MiceCirculation, 2003
- TSC1–TSC2: a complex tale of PKB-mediated S6K regulationNature, 2002
- Negative Regulation of Protein Translation by Mitogen-Activated Protein Kinase-Interacting Kinases 1 and 2Molecular and Cellular Biology, 2001
- The p38 MAPK Pathway Is Required for Cell Growth Inhibition of Human Breast Cancer Cells in Response to ActivinPublished by Elsevier BV ,2001
- Specificity and mechanism of action of some commonly used protein kinase inhibitorsBiochemical Journal, 2000
- Molecular basis for the substrate specificity of protein kinase B; comparison with MAPKAP kinase‐1 and p70 S6 kinaseFEBS Letters, 1996
- Oncogenic Raf-1 Activates p70 S6 Kinase via a Mitogen-activated Protein Kinase-independent PathwayPublished by Elsevier BV ,1996
- A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye bindingAnalytical Biochemistry, 1976