Diabetes, Vol 38, Issue 5 544-549, Copyright © 1989 by American Diabetes Association

ARTICLES

Insulin and ribosomal protein S6 kinase in rat pancreatic acini

CK Sung and JA Williams
Department of Physiology, University of California, San Francisco.

Treatment of pancreatic acini from diabetic rats with insulin resulted in a dose-dependent increase in the phosphorylation of ribosomal protein S6 when analyzed by two-dimensional gel electrophoresis. To study the presence of the protein kinase mediating this phosphorylation, soluble extracts of intact acini that had been previously treated with insulin were prepared and assayed for protein kinase activity with rat pancreatic ribosomes as a substrate. Activation of S6 kinase activity, observed in a time-dependent manner, was maximal after 20-30 min and, in a dose-dependent manner, was half-maximal at 1 nM and maximal at 10 nM insulin concentration. Based on cofactor requirements, substrate specificity, and a slow activation of the enzyme, the S6 kinase was distinct from cAMP-dependent, Ca2+-calmodulin-dependent, and Ca2+-phospholipid-dependent protein kinases and protease-activated kinase II. The S6 kinase activated by insulin was highly specific for the ribosomal protein S6 when compared with various substrates, including casein, glycogen synthase, phosphorylase b, phosvitin, histone HIII-S, and histone HVIII-S. Protein S6 phosphorylation in intact acini and activation of the S6 kinase by insulin showed similar dose-response curves, consistent with the S6 kinase being responsible for the protein S6 phosphorylation in intact acini. The comparison of the dose-response curves for S6 phosphorylation and protein synthesis in acini suggests that there is a close correlation between these two insulin actions.
CiteULike    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				M. D. Sans, M. Tashiro, N. L. Vogel, S. R. Kimball, L. G. D'Alecy, and J. A. Williams Leucine Activates Pancreatic Translational Machinery in Rats and Mice through mTOR Independently of CCK and Insulin J. Nutr., July 1, 2006; 136(7): 1792 - 1799. [Abstract] [Full Text] [PDF]

				M. D. Sans, S.-H. Lee, L. G. D'Alecy, and J. A. Williams Feeding activates protein synthesis in mouse pancreas at the translational level without increase in mRNA Am J Physiol Gastrointest Liver Physiol, September 1, 2004; 287(3): G667 - G675. [Abstract] [Full Text] [PDF]