Expression in mammalian cell cultures reveals interdependent, but distinct, functions for Star and Rhomboid proteins in the processing of the Drosophila transforming-growth-factor-alpha homologue Spitz.
We report here distinct interdependent functions for two proteins, Star and Rhomboid, that are key determinants of the epidermal-growth-factor (EGF)-receptor signalling pathway in Drosophila. When we expressed the Drosophila EGF-receptor ligand Spitz in mammalian cells, the protein failed to traffic to the plasma membrane, as assessed by either cell-surface protein biotinylation or immunocytochemical staining. However, when we co-expressed Star with Spitz, trafficking of Spitz to the cell surface could be demonstrated. Only when we co-expressed Spitz, Star and Rhomboid could the release of soluble Spitz protein into the medium be shown. Taken together, our results indicate that Star is required for the intracellular trafficking of Spitz, and that Rhomboid is essential for the release of soluble Spitz protein from cells.
Pascall
John C
JC
Signalling Programme, The Babraham Institute, Babraham, Cambridge CB2 4AT, U.K.
Luck
Jane E
JE
Brown
Kenneth D
KD
D000818:Animals; D001693:Biological Transport, Active; D019556:COS Cells; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004330:Drosophila / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D012995:Solubility; D014162:Transfection; D016211:Transforming Growth Factor alpha / Q000235:genetics / Q000378:metabolism*
D029721:Drosophila Proteins; D008565:Membrane Proteins; D011994:Recombinant Proteins; C081481:Rho protein, Drosophila; C415248:S protein, Drosophila; C472498:Stet protein, Drosophila; D016211:Transforming Growth Factor alpha; C076026:spi protein, Drosophila; D004815:Epidermal Growth Factor; D066246:ErbB Receptors