Characterization of growth hormone-induced tyrosine-phosphorylated proteins in mouse cells that express GH receptors.
Following the growth hormone (GH) and GH receptor (R) interaction, the receptor and Janus tyrosine kinase 2 (JAK2) become tyrosine phosphorylated along with other intracellular proteins. Previously, we reported that GH induces tyrosine phosphorylation of intracellular proteins with molecular masses of approx 95 kDa (pp95) in mouse 3T3-F442A preadipocytes and in mouse L-cells that express recombinant GHRs. We have studied this GH-induced phosphorylation event in greater detail. Three proteins with apparent molecular masses of 93, 95, and 96 kDa showed increased tyrosine phosphorylation in a time-dependent manner following GH treatment of cells that express GH receptors. GH-induced tyrosine phosphorylation of these proteins is independent of activation of protein kinase C (PKC). Cell fractionation studies revealed that the majority of tyrosine-phosphorylated pp95/96 is located in the cytoplasm. pp95 and pp96 have pIs of approx 6.2. Immunoprecipitation and Western blot analyses revealed that pp93 and pp95/96 are not immunologically related with Stat1, Stat3, Stat4, JAK2, and GHR. Thus, pp93 and pp95/96 may be important GH signal transducers independent of PKC activation and different from the characterized members in the JAK-STAT pathway.
Xu
B C
BC
Department of Biological Sciences, Ohio University, Athens 45701, USA.
Wang
X
X
James
C
C
Kopchick
J J
JJ
D000818:Animals; D015153:Blotting, Western; D002451:Cell Compartmentation; D002458:Cell Fractionation; D015180:Electrophoresis, Gel, Two-Dimensional; D013006:Growth Hormone / Q000494:pharmacology*; D007739:L Cells; D051379:Mice; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D011493:Protein Kinase C; D011986:Receptors, Somatotropin / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
D010750:Phosphoproteins; D011986:Receptors, Somatotropin; D013006:Growth Hormone; D011493:Protein Kinase C