TY - JOUR
T1 - Insulin regulation of protein translation repressor 4E-BP1, an eIF4E-binding protein, in renal epithelial cells
AU - Bhandari, Basant K.
AU - Feliers, Denis
AU - Duraisamy, Senthil
AU - Stewart, Jennifer L.
AU - Gingras, Anne Claude
AU - Abboud, Hanna E.
AU - Choudhury, Goutam Ghosh
AU - Sonenberg, Nahum
AU - Kasinath, Balakuntalam S.
PY - 2001
Y1 - 2001
N2 - Background. Augmented protein translation by insulin involves activation of eukaryotic initiation factor 4E (eIF4E) that follows release of eIF4E from a heterodimeric complex by phosphorylation of its inhibitory binding protein, 4E-BP1. We examined insulin regulation of 4E-BP1 phosphorylation in murine proximal tubular epithelial cells. Methods and Results. Insulin (1 nmol/L) increased de novo protein synthesis by 58 ± 11% (P < 0.001). Insulin also augmented 4E-BP1 phosphorylation and phosphatidylinositol 3-kinase (PI 3-kinase) activity in antiphosphotyrosine immunoprecipitates. This could be prevented by PI 3-kinase inhibitors, Wortmannin, and LY294002. Insulin also activated Akt that lies downstream of PI 3-kinase. Rapamycin abrogated 4E-BP1 phosphorylation in response to insulin, suggesting involvement of mammalian target of rapamycin (mTOR), a kinase downstream of Akt. Insulin-stimulated phosphorylation of 4E-BP1 was also inhibited by PD098059, implying involvement of Erk-1/-2 mitogen-activated protein (MAP) kinase. An increase in Erk-1/-2 type MAP kinase activity by insulin was directly confirmed in an immunokinase assay and was found to be PI 3-kinase dependent. Conclusions. In proximal tubular epithelial cells, insulin augments 4E-BP1 phosphorylation, which is PI 3-kinase and mTOR dependent. The requirement for Erk-1/-2 MAP kinase activation for 4E-BP1 phosphorylation by insulin suggests a cross-talk between PI 3-kinase and Erk-1/-2-type MAP kinase pathways.
AB - Background. Augmented protein translation by insulin involves activation of eukaryotic initiation factor 4E (eIF4E) that follows release of eIF4E from a heterodimeric complex by phosphorylation of its inhibitory binding protein, 4E-BP1. We examined insulin regulation of 4E-BP1 phosphorylation in murine proximal tubular epithelial cells. Methods and Results. Insulin (1 nmol/L) increased de novo protein synthesis by 58 ± 11% (P < 0.001). Insulin also augmented 4E-BP1 phosphorylation and phosphatidylinositol 3-kinase (PI 3-kinase) activity in antiphosphotyrosine immunoprecipitates. This could be prevented by PI 3-kinase inhibitors, Wortmannin, and LY294002. Insulin also activated Akt that lies downstream of PI 3-kinase. Rapamycin abrogated 4E-BP1 phosphorylation in response to insulin, suggesting involvement of mammalian target of rapamycin (mTOR), a kinase downstream of Akt. Insulin-stimulated phosphorylation of 4E-BP1 was also inhibited by PD098059, implying involvement of Erk-1/-2 mitogen-activated protein (MAP) kinase. An increase in Erk-1/-2 type MAP kinase activity by insulin was directly confirmed in an immunokinase assay and was found to be PI 3-kinase dependent. Conclusions. In proximal tubular epithelial cells, insulin augments 4E-BP1 phosphorylation, which is PI 3-kinase and mTOR dependent. The requirement for Erk-1/-2 MAP kinase activation for 4E-BP1 phosphorylation by insulin suggests a cross-talk between PI 3-kinase and Erk-1/-2-type MAP kinase pathways.
KW - Cell signaling
KW - Eukaryotic initiation factor 4E binding protein-1
KW - MAP kinase
KW - Protein synthesis
KW - Proximal tubule cell
KW - Tubular epithelial cells
KW - Type 2 diabetes
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U2 - 10.1046/j.1523-1755.2001.059003866.x
DO - 10.1046/j.1523-1755.2001.059003866.x
M3 - Article
C2 - 11231341
AN - SCOPUS:0035092268
SN - 0085-2538
VL - 59
SP - 866
EP - 875
JO - Kidney International
JF - Kidney International
IS - 3
ER -