Localization of the type 3 inositol 1,4,5-trisphosphate receptor in the Ca2+ wave trigger zone of pancreatic acinar cells.
Agonist-induced cytosolic Ca2+ (Ca2+i) signals begin as apical-to-basal Ca2+i waves in pancreatic acinar cells and in other polarized epithelia. However, the basis of this polarized Ca2+i signaling pattern is unknown. Here we use immunocytochemistry to demonstrate that the type 3 inositol trisphosphate receptor is localized to the extreme apex of pancreatic acinar cells, the region which corresponds to the trigger zone from which Ca2+i signals originate in this cell type (Kasai, H., Li, Y.X., and Miyashita, Y. (1993) Cell 74, 669-677). We also show that inositol trisphosphate-mediated Ca2+ release induces amylase release from permeabilized pancreatic acini. Since Ca2+i signals begin by inositol trisphosphate-mediated Ca2+ release, these findings suggest that localization of the type 3 inositol trisphosphate receptor to the trigger zone is responsible for the generation of apical-to-basal Ca2+i waves, and that this organization may be important for regulating apical exocytosis in pancreatic acinar cells.
Nathanson
M H
MH
Liver Center, Yale University School of Medicine, New Haven, Connecticut 06510.
Fallon
M B
MB
Padfield
P J
PJ
Maranto
A R
AR
D000681:Amylases / Q000378:metabolism; D000818:Animals; D000906:Antibodies; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000032:analysis / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D007150:Immunohistochemistry; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008297:Male; D010179:Pancreas / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis / Q000378:metabolism*; D015398:Signal Transduction
D000906:Antibodies; D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D015544:Inositol 1,4,5-Trisphosphate; D000681:Amylases; D002118:Calcium