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  • Mechanisms of JAK/STAT pathway negative regulation by the short coreceptor Eye Transformer/Latran.

Mechanisms of JAK/STAT pathway negative regulation by the short coreceptor Eye Transformer/Latran.

Molecular biology of the cell (2015-12-15)
Katherine H Fisher, Wojciech Stec, Stephen Brown, Martin P Zeidler
ABSTRACT

Transmembrane receptors interact with extracellular ligands to transduce intracellular signaling cascades, modulate target gene expression, and regulate processes such as proliferation, apoptosis, differentiation, and homeostasis. As a consequence, aberrant signaling events often underlie human disease. Whereas the vertebrate JAK/STAT signaling cascade is transduced via multiple receptor combinations, the Drosophila pathway has only one full-length signaling receptor, Domeless (Dome), and a single negatively acting receptor, Eye Transformer/Latran (Et/Lat). Here we investigate the molecular mechanisms underlying Et/Lat activity. We demonstrate that Et/Lat negatively regulates the JAK/STAT pathway activity and can bind to Dome, thus reducing Dome:Dome homodimerization by creating signaling-incompetent Dome:Et/Lat heterodimers. Surprisingly, we find that Et/Lat is able to bind to both JAK and STAT92E but, despite the presence of putative cytokine-binding motifs, does not detectably interact with pathway ligands. We find that Et/Lat is trafficked through the endocytic machinery for lysosomal degradation but at a much slower rate than Dome, a difference that may enhance its ability to sequester Dome into signaling-incompetent complexes. Our data offer new insights into the molecular mechanism and regulation of Et/Lat in Drosophila that may inform our understanding of how short receptors function in other organisms.

MATERIALS
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Brand
Product Description

Sigma-Aldrich
Monoclonal ANTI-FLAG® M2 antibody produced in mouse, clone M2, purified immunoglobulin (Purified IgG1 subclass), buffered aqueous solution (10 mM sodium phosphate, 150 mM NaCl, pH 7.4, containing 0.02% sodium azide)
Sigma-Aldrich
Anti-Phosphotyrosine Antibody, clone PY20, clone PY20, Upstate®, from mouse