TY - JOUR AB - Protein phosphorylation is an important mechanism that controls many cellular activities. Phosphorylation of a given protein is precisely controlled by two opposing biochemical reactions catalyzed by protein kinases and protein phosphatases. How these two opposing processes are coordinated to achieve regulation of protein phosphorylation is unresolved. We have developed a novel experimental approach to directly study protein dephosphorylation in cells. We determined the kinetics of dephosphorylation of insulin receptor substrate-1/2, Akt, and ERK1/2, phosphoproteins involved in insulin receptor signaling. We found that insulin-induced ERK1/2 and Akt kinase activities were completely abolished 10 min after inhibition of the corresponding upstream kinases with PD98059 and LY294002, respectively. In parallel experiments, insulin-induced phosphorylation of Akt, ERK1/2, and insulin receptor substrate-1/2 was decreased and followed similar kinetics. Our findings suggest that these proteins are dephosphorylated by a default mechanism, presumably via constitutively active phosphatases. However, dephosphorylation of these proteins is overcome by activation of protein kinases following stimulation of the insulin receptor. We propose that, during acute insulin stimulation, the kinetics of protein phosphorylation is determined by the interplay between upstream kinase activity and dephosphorylation by default. AD - Section of Endocrinology, The University of Chicago, Chicago, Illinois 60637, USA. AN - 17068339 AU - Zhande, R. AU - Zhang, W. AU - Zheng, Y. AU - Pendleton, E. AU - Li, Y. AU - Polakiewicz, R. D. AU - Sun, X. J. DA - Dec 22 DO - 10.1074/jbc.M605251200 ET - 2006/10/28 J2 - The Journal of biological chemistry KW - Animals CHO Cells Cell Line Cricetinae Enzyme Inhibitors/pharmacology Flavonoids/pharmacology Hepatocytes/metabolism Humans Insulin Receptor Substrate Proteins Intracellular Signaling Peptides and Proteins Mice Mitogen-Activated Protein Kinase 1/*metabolism Mitogen-Activated Protein Kinase 3/*metabolism Phosphoproteins/*biosynthesis Phosphorylation Proto-Oncogene Proteins c-akt/*metabolism LA - eng M1 - 51 M3 - Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't N1 - Zhande, Rachel Zhang, Wenshuo Zheng, Yanbin Pendleton, Elisha Li, Yu Polakiewicz, Roberto D Sun, Xiao Jian R01 DK060128/DK/NIDDK NIH HHS/ J Biol Chem. 2006 Dec 22;281(51):39071-80. Epub 2006 Oct 26. PY - 2006 SN - 0021-9258 (Print) 0021-9258 (Linking) SP - 39071-80 ST - Dephosphorylation by default, a potential mechanism for regulation of insulin receptor substrate-1/2, Akt, and ERK1/2 T2 - J Biol Chem TI - Dephosphorylation by default, a potential mechanism for regulation of insulin receptor substrate-1/2, Akt, and ERK1/2 UR - http://www.ncbi.nlm.nih.gov/pubmed/17068339 VL - 281 ID - 137 ER -