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Functional analysis of leptin receptor activation using a Janus kinase/signal transducer and activator of

Lennart Zabeau1, Delphine Defeau, José Van der Heyden

  • 1Flanders Interuniversity Institute for Biotechnology, VIB09, Department of Medical Protein Research, Ghent University, Faculty of Medicine and Health Sciences, Baertsoenkaai 3, B-9000 Ghent, Belgium.

Molecular Endocrinology (Baltimore, Md.)
|October 4, 2003
PubMed

The leptin receptor (LR), a member of the class I cytokine receptor family, is composed of a single subunit. Its extracellular domain consists of two so-called cytokine receptor homology domains, separated by an Ig-like domain, and two additional fibronectin type III modules. Requirements for LR activation were examined using a complementation strategy. Two LR mutants, LR-FFY-Deltabox 1 and LR-F3, deficient in Janus kinase or signal transducer and activator of transcription (STAT) activation, respectively, were only able to generate a STAT3-dependent signal when coexpressed. Based on the requirements for Janus kinase/STAT signaling, and on the lack of complementation with similar receptor constructs, but containing the extracellular domain of the homodimeric erythropoietin receptor, this observation can be explained only by higher order LR clustering. Using a panel of deletion mutants we were able to define a role for the cytokine receptor homology 1 and Ig-like domains in leptin signaling. Moreover, we demonstrate a nonredundant function for the individual receptor chains within the homomeric LR complex. Based on these data, we propose a possible model for LR clustering.

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