Growth hormone promotes the association of transcription factor STAT5 with the growth hormone receptor.

Members of the cytokine/growth hormone (GH)/prolactin receptor superfamily transduce signals by association and activation of JAK tyrosine kinases. For GH receptor (GHR), both JAK2 and the GHR undergo tyrosine phosphorylation upon GH stimulation. Also, GH has recently been shown to activate the transcription factor by tyrosine phosphorylation. In the present study, we demonstrate that GH induces rapid tyrosine phosphorylation of different isoforms of duanyu18135 in mouse L cells stably transfected with a cDNA encoding porcine GHR (pGHR). In this cell system, duanyu18135 directly interacts with the GHR in a GH-dependent manner. Additionally, GH-induced tyrosine phosphorylation of duanyu18135 and the interaction of duanyu18135 with GHR can be observed in mouse 3T3-F442A cells which express endogenous mouse GHR. Interestingly, when cDNAs encoding the two mouse duanyu18135 homologs and were individually transfected into mouse L cells expressing pGHR, only demonstrated the ability to interact with the pGHR and subsequently underwent GH-dependent tyrosine phosphorylation. did not. Therefore, the GH-dependent interaction of a particular duanyu18135 with tyrosine-phosphorylated GHR may play an important role in GH-mediated signal transduction.

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