Growth hormone stimulates the tyrosine kinase activity of JAK2 and induces tyrosine phosphorylation of insulin receptor substrates and Shc in rat tissues.
GH stimulates the tyrosine phosphorylation of various cellular polypeptides, including the GH receptor itself, in an early part of the intracellular response. Some of these phosphorylations are catalyzed by a GH receptor-associated kinase identified as JAK2, a member of the Janus family of tyrosine kinases. In cultured cells, GH stimulates the tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1), IRS-2, and Shc. This study investigated whether GH could cause the tyrosine phosphorylation of IRSs and Shc proteins in fasted rat tissues in vivo. GH was administered to fasted Wistar rats via a portal vein, and extracts of different tissues were immunoprecipitated with specific antibodies. GH increased the tyrosine phosphorylation of IRS-1, IRS-2, JAK2, and Shc proteins in the liver, heart, kidney, muscle, and adipose tissue of rats. The roles of these substrates as signaling molecules for GH were further demonstrated by the finding that GH stimulated the association of IRS-1/2 with phosphatidylinositol 3-kinase, Grb2, and phosphotyrosine phosphatase and of Shc with Grb2. The correlation between JAK2 tyrosyl phosphorylation and IRS-1 tyrosyl phosphorylation in response to GH together with the results of the in vitro tyrosine kinase assay are consistent with the hypothesis that JAK2 may mediate GH-induced phosphorylation of IRS-1.
Thirone
A C
AC
Departamento de Clínica Médica, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, SP, Brazil.
Carvalho
C R
CR
Saad
M J
MJ
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D051380:GRB2 Adaptor Protein; D013006:Growth Hormone / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D053614:Janus Kinase 2; D008297:Male; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D051381:Rats; D017208:Rats, Wistar; D011972:Receptor, Insulin / Q000378:metabolism*; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014443:Tyrosine / Q000378:metabolism*; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D051380:GRB2 Adaptor Protein; C495950:Grb2 protein, rat; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; C526296:Irs1 protein, rat; C526299:Irs2 protein, rat; D010750:Phosphoproteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D055765:Shc Signaling Adaptor Proteins; C528035:Shc1 protein, rat; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014443:Tyrosine; D013006:Growth Hormone; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; C507927:Jak2 protein, rat; D053614:Janus Kinase 2; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516727:Ptpn11 protein, rat; C509250:Ptpn6 protein, rat; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases