Growth hormone-induced signal transduction depends on an intact ubiquitin system

Ger J. Strous, Peter Van Kerkhof, Roland Covers, Peter Rotwein, Alan L. Schwartz

    Research output: Contribution to journalArticlepeer-review

    55 Scopus citations

    Abstract

    The growth hormone receptor (GHR) is a ubiquitinated cell surface protein. Ligand binding and receptor dimerization activate the cytosolic kinase Jak2. This event initiates signal transduction via STAT proteins. Expression of GHR in a Chinese hamster ovary (CHO) cell line, which exhibits a temperature-sensitive defect in ubiquitin conjugation (CHO-ts20), as well as in wild type cells (CHO-E36) has shown that endocytosis of the receptor requires an intact ubiquitin conjugation system (Strous G. J., van Kerkhof, P., Govers, R., Ciechanover A., and Schwartz, A. L. (1996) EMBO J. 15, 3806- 3812). We have now examined the requirement for ubiquitin conjugation in growth factor-mediated signal transduction. In CHO-E36 and in CHO-ts20 cells at the permissive temperature, STAT proteins were activated in a growth factor-dependent fashion. However, no activation of STAT proteins was observed at the nonpermissive temperature in CHO-ts20 cells. Neither tyrosine phosphorylation of GHR nor of Jak2 was inhibited at the nonpermissive temperature. When tyrosine phosphorylation was inhibited following treatment with staurosporin, ubiquitination of the receptor proceeded normally. Furthermore, mutation of GHR phenylalanine-327, which prevents GHR endocytosis, inhibited receptor ubiquitination but allowed normal Jak/STAT- mediated signal transduction. Thus, these data provide evidence that the ubiquitin conjugation system is involved in the Jak/STAT signaling pathway, be it not at the initial stage(s) of Jak2 activity.

    Original languageEnglish (US)
    Pages (from-to)40-43
    Number of pages4
    JournalJournal of Biological Chemistry
    Volume272
    Issue number1
    DOIs
    StatePublished - 1997

    ASJC Scopus subject areas

    • Biochemistry
    • Molecular Biology
    • Cell Biology

    Fingerprint Dive into the research topics of 'Growth hormone-induced signal transduction depends on an intact ubiquitin system'. Together they form a unique fingerprint.

    Cite this