A synthetic peptide of the effector domain of rab3A stimulates inositol 1,4,5-trisphosphate production in digitonin-permeabilized pancreatic acini.
In this study we report that a synthetic peptide of the effector domain of rab3A (rab3AL(33-48)) stimulates both amylase secretion and inositol 1,4,5-trisphosphate (IP3)-accumulation in digitonin-permeabilized pancreatic acini in an analogous way to cholecystokinin-octapeptide (CCK8). Maximum CCK8-induced IP3-accumulation was observed at five seconds after addition of CCK8 to the acini. Maximum rab3AL(33-48)-induced IP3-production occurred 15 to 30 seconds after addition of rab3AL(33-48); then the acinar IP3 content declined towards the basal level. Heparin, an inhibitor of IP3 binding to its receptor, inhibited both rab3AL(33-48)- and CCK8-stimulated amylase secretion without affecting the response to vasoactive intestinal polypeptide. rab3AL(33-48) had no effect in intact acini, indicating that the site of action of rab3AL(33-48) is intracellular. We conclude that rab-like small molecular weight GTP-binding proteins regulate phospholipase C activity and thereby amylase secretion from inside of the cell.
Piiper
A
A
Department of Internal Medicine, University of Frankfurt/Main, Germany.
Stryjek-Kaminska
D
D
Stein
J
J
Caspary
W F
WF
Zeuzem
S
S
D000681:Amylases / Q000378:metabolism; D000818:Animals; D002463:Cell Membrane Permeability; D004072:Digitonin; D019204:GTP-Binding Proteins / Q000502:physiology*; D006493:Heparin / Q000494:pharmacology; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D007700:Kinetics; D009419:Nerve Tissue Proteins / Q000494:pharmacology*; D010179:Pancreas / Q000187:drug effects / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology*; D051381:Rats; D012844:Sincalide / Q000494:pharmacology; D013997:Time Factors; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology; D020692:rab3 GTP-Binding Proteins
D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D014660:Vasoactive Intestinal Peptide; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D000681:Amylases; D019204:GTP-Binding Proteins; D020692:rab3 GTP-Binding Proteins; D004072:Digitonin; D012844:Sincalide