This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Taler, M. Articles by Nir, U. Search for Related Content PubMed PubMed Citation Articles by Taler, M. Articles by Nir, U. Pubmed/NCBI databases Domain Gene GEO Profiles HomoloGene UniGene Compound via MeSH Substance via MeSH Genetics Home Reference Hazardous Substances DB L-TYROSINE

Fer Is a Downstream Effector of Insulin and Mediates the Activation of Signal Transducer and Activator of Transcription 3 in Myogenic Cells

Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel

Address all correspondence and requests for reprints to: Professor Uri Nir, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel. E-mail: nir{at}mail.biu.ac.il.

Fer is an intracellular tyrosine kinase that associates with signal transducer and activator of transcription 3 (Stat3) in mammalian cells. However, the signaling pathways in which this interaction plays a functional role have not been revealed. Herein, we show that insulin up-regulates the levels of the fer mRNA and Fer protein in myoblasts that undergo insulin-induced myogenic differentiation. Moreover, insulin directs the interaction of Fer with members of the Janus family of tyrosine kinases (Jak)-Stat3 signaling pathway. Although in untreated cells Fer binds Jak1 and its tyrosine phosphorylation level is low, insulin treatment induced the phosphorylation of Fer and its dissociation from Jak1.

The up-regulation of Fer and its dissociation from Jak1 were accompanied by an augmented association of activated Fer with Stat3 and by a concomitant increase in the tyrosine phosphorylation of Stat3. Dissociation of Fer and Jak1, as well as elevation in the level of Fer and in the tyrosine phosphorylation of Stat3, depended on the activity of phosphatidylinositol 3-kinase (PI3K) and was abolished by a PI3K inhibitor. However, Fer and Stat3 were only mildly affected by low concentrations of IGF-I, another activator of the PI3K pathway that can also induce myogenic differentiation. RNA interference directed toward the fer mRNA did not affect the cellular levels of Stat3 but led to a dramatic reduction in the tyrosine phosphorylation level of this transcription factor. Thus, Fer is a downstream effector of insulin and mediates the activation of Stat3 in myogenic cells.