title: Synthetic peptides of the effector-binding domain of rab enhance secretion from digitonin-permeabilized chromaffin cells.
abstract: There is evidence that the rab class of low molecular weight GTP-binding proteins is involved in vesicular transfer from endoplasmic reticulum to Golgi and between Golgi cisternae. To determine whether similar proteins play a role in regulated exocytosis, the effects of synthetic peptides derived from low molecular weight GTP-binding proteins on catecholamine secretion from digitonin-permeabilized chromaffin cells were investigated. The synthetic peptides represent the putative effector-binding domains of the rab, ras and ral classes of low molecular weight GTP-binding proteins and correspond to ras(33-48). Two rab peptides but neither a ras nor a ral peptide enhanced Ca(2+)-dependent secretion by approximately 30%. Maximal secretion in response to Ca2+ was increased. The enhancement was not blocked by the pseudosubstrate inhibitor of protein kinase C, PKC(19-31), thus indicating that activation of protein kinase C was not responsible for the enhancement of secretion. Similarly a rab peptide but neither a ras nor a ral peptide enhanced GppNHp-induced secretion 30-70%. The peptides had little or no effect in the absence of Ca2+ or GppNHp. The data are consistent with a protein of the rab class playing a role in regulated exocytosis.
authors.affiliation: Department of Pharmacology, University of Michigan Medical School, Ann Arbor 48109-0626.
authors.forename: J
authors.initials: J
authors.lastname: Senyshyn
authors.forename: W E
authors.initials: WE
authors.lastname: Balch
authors.forename: R W
authors.initials: RW
authors.lastname: Holz
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects; D004072:Digitonin; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D008954:Models, Biological; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism* / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology*; D020692:rab3 GTP-Binding Proteins
chemical_list: D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D006165:Guanylyl Imidodiphosphate; D000255:Adenosine Triphosphate; D019204:GTP-Binding Proteins; D020692:rab3 GTP-Binding Proteins; D004072:Digitonin; D002118:Calcium