Activated release of membrane-anchored TGF-alpha in the absence of cytosol.
The ectodomain of proTGF-alpha, a membrane-anchored growth factor, is converted into soluble TGF-alpha by a regulated cellular proteolytic system that recognizes proTGF-alpha via the C-terminal valine of its cytoplasmic tail. In order to define the biochemical components involved in proTGF-alpha cleavage, we have used cells permeabilized with streptolysin O (SLO) that have been extensively washed to remove cytosol. PMA, acting through a Ca(2+)-independent protein kinase C, activates cleavage as efficiently in permeabilized cells as it does in intact cells. ProTGF-alpha cleavage is also stimulated by GTP gamma S through a mechanism whose pharmacological properties suggest the involvement of a heterotrimeric G protein acting upstream of the PMA-sensitive Ca(2+)-independent protein kinase C. Activated proTGF-alpha cleavage is dependent on ATP hydrolysis, appears not to require vesicular traffic, and acts specifically on proTGF-alpha that has reached the cell surface. These results indicate that proTGF-alpha is cleaved from the cell surface by a regulated system whose signaling, recognition, and proteolytic components are retained in cells devoid of cytosol.
Bosenberg
M W
MW
Cell Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, New York 10021.
Pandiella
A
A
Massagué
J
J
D000535:Aluminum / Q000494:pharmacology; D017607:Aluminum Compounds; D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D002463:Cell Membrane Permeability; D006224:Cricetinae; D005459:Fluorides; D005461:Fluorine / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D007700:Kinetics; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D014162:Transfection; D016211:Transforming Growth Factor alpha / Q000096:biosynthesis* / Q000378:metabolism*
D017607:Aluminum Compounds; D011498:Protein Precursors; D011994:Recombinant Proteins; D013873:Thionucleotides; D016211:Transforming Growth Factor alpha; C052268:protransforming growth factor alpha; D006153:Guanosine Diphosphate; C050992:tetrafluoroaluminate; D005461:Fluorine; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C023427:guanosine 5'-O-(2-thiodiphosphate); D000535:Aluminum; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate; D005459:Fluorides