Drosophila appear to express a single Janus kinase [(JAK), termed hopscotch (Hop)], and signal transducer and activators of transcription [(STATs), termed STAT92E], and one extracellular ligand [termed Unpaired (UPD)] that activates the signaling pathway. Now, the long-sought receptor in the pathway has been identified. Chen et al. have cloned the transmembrane protein Master of Marelle (Mom). Flies containing Mom mutations exhibited the same phenotype--embryos from –/– Mom flies die and have defects in body segmentation--as flies with hop or STAT92E mutations. Loss-of-function Mom mutants were rescued by the constitutively activated hop mutant hopTum-l, suggesting that Mom is located upstream of Hop in the same pathway. The authors also demonstrated that UPD and STAT92E bound to Mom in cells. The sequence of Mom indicated that it is distantly related to members of the glycoprotein (gp)130 family of cytokine receptors. Some receptors within the gp130 family must homodimerize before propagating a signal, whereas other members of the family must heterodimerize for proper signaling. Thus, the possibility exists that other receptor subunits, or indeed other receptors, that have yet to be characterized may exist in the Drosophila "JAK-STAT" pathway.
H.-W. Chen, X. Chen, S.-W. Oh, M. J. Marinissen, J. S. Gutkind, S. X. Hou, mom identifies a receptor for the Drosophila JAK/STAT signal transduction pathway and encodes a protein distantly related to the mammalian cytokine receptor family. Genes Dev. 16, 388-398 (2002). [Abstract] [Full Text]