TY - JOUR

T1 - Growth hormone-dependent phosphorylation of tyrosine 333 and/or 338 of the growth hormone receptor

AU - VanderKuur, J A

AU - Wang, X

AU - Zhang, L

AU - Allevato, G

AU - Billestrup, Nils

AU - Carter-Su, C

PY - 1995/9/15

Y1 - 1995/9/15

N2 - Many signaling pathways initiated by ligands that activate receptor tyrosine kinases have been shown to involve the binding of SH2 domain-containing proteins to specific phosphorylated tyrosines in the receptor. Although the receptor for growth hormone (GH) does not contain intrinsic tyrosine kinase activity, GH has recently been shown to promote the association of its receptor with JAK2 tyrosine kinase, to activate JAK2, and to promote the tyrosyl phosphorylation of both GH receptor (GHR) and JAK2. In this work, we examined whether tyrosines 333 and/or 338 in GHR are phosphorylated by JAK2 in response to GH. Tyrosines 333 and 338 in rat full-length (GHR1-638) and truncated (GHR1-454) receptor were replaced with phenylalanines and the mutated GHRs expressed in Chinese hamster ovary cells. These substitutions caused a loss of GH-dependent tyrosyl phosphorylation of truncated receptor and a reduction of GH-dependent phosphorylation of the full-length receptor. Consistent with Tyr333 and/or Tyr338 serving as substrates of JAK2, these substitutions resulted in a loss of tyrosyl phosphorylation of truncated receptor in an in vitro kinase assay using substantially purified GH.GHR.JAK2 complexes. The Tyr to Phe substitutions did not substantially alter GH-dependent JAK2 association with GHR or tyrosyl phosphorylation of JAK2. These results suggest that Tyr333 and/or Tyr338 in GHR are phosphorylated in response to GH and may therefore serve as binding sites for SH2 domain-containing proteins in GH signal transduction pathways.

AB - Many signaling pathways initiated by ligands that activate receptor tyrosine kinases have been shown to involve the binding of SH2 domain-containing proteins to specific phosphorylated tyrosines in the receptor. Although the receptor for growth hormone (GH) does not contain intrinsic tyrosine kinase activity, GH has recently been shown to promote the association of its receptor with JAK2 tyrosine kinase, to activate JAK2, and to promote the tyrosyl phosphorylation of both GH receptor (GHR) and JAK2. In this work, we examined whether tyrosines 333 and/or 338 in GHR are phosphorylated by JAK2 in response to GH. Tyrosines 333 and 338 in rat full-length (GHR1-638) and truncated (GHR1-454) receptor were replaced with phenylalanines and the mutated GHRs expressed in Chinese hamster ovary cells. These substitutions caused a loss of GH-dependent tyrosyl phosphorylation of truncated receptor and a reduction of GH-dependent phosphorylation of the full-length receptor. Consistent with Tyr333 and/or Tyr338 serving as substrates of JAK2, these substitutions resulted in a loss of tyrosyl phosphorylation of truncated receptor in an in vitro kinase assay using substantially purified GH.GHR.JAK2 complexes. The Tyr to Phe substitutions did not substantially alter GH-dependent JAK2 association with GHR or tyrosyl phosphorylation of JAK2. These results suggest that Tyr333 and/or Tyr338 in GHR are phosphorylated in response to GH and may therefore serve as binding sites for SH2 domain-containing proteins in GH signal transduction pathways.

KW - Amino Acid Sequence

KW - Animals

KW - CHO Cells

KW - Cricetinae

KW - Enzyme Activation

KW - Growth Hormone

KW - Humans

KW - Janus Kinase 2

KW - Mutagenesis, Site-Directed

KW - Phenylalanine

KW - Phosphoproteins

KW - Phosphorylation

KW - Phosphotyrosine

KW - Point Mutation

KW - Protein-Tyrosine Kinases

KW - Proto-Oncogene Proteins

KW - Rats

KW - Receptors, Somatotropin

KW - Recombinant Proteins

KW - Sequence Deletion

KW - Transfection

KW - Tyrosine

M3 - Journal article

C2 - 7545168

VL - 270

SP - 21738

EP - 21744

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 37

ER -