title: Endoplasmic reticulum Ca(2+)-ATPase inhibitors stimulate membrane guanylate cyclase in pancreatic acinar cells.
abstract: In this study, we show that particulate guanylate cyclase (GC) is present in rat pancreatic acinar cells and is located both on plasma membrane and membranes of endoplasmic reticulum (ER). Western blot analysis indicates that the enzyme isoform GC-A is present in the acinar cell membranes. The specific inhibitors of ER Ca(2+)-ATPase thapsigargin, 2,5-di-(t-butyl)-1,4-hydroquinone (BHQ), and cyclopiazonic acid all activated particulate GC in pancreatic acini, both in membrane fractions and intact cells. These inhibitors also induced dephosphorylation of GC. Dose dependencies of Ca(2+)-ATPase inhibition and GC activation by BHQ are very similar, and those for thapsigargin partially overlap. ER Ca(2+)-ATPase and GC are coimmunoprecipitated both by antisera against membrane GC and by antisera against ER Ca(2+)-ATPase, suggesting a physical association between the two enzymes. The results suggest that thapsigargin and the other inhibitors act through ER Ca(2+)-ATPase to activate membrane GC in pancreatic acinar cells, although their direct effect on GC cannot be excluded.
authors.affiliation: Departments of Medicine, Veterans Affairs Greater Los Angeles Healthcare System and University of California, Los Angeles, California 90073, USA. agukovsk@ucla.edu
authors.forename: A S
authors.initials: AS
authors.lastname: Gukovskaya
authors.forename: S
authors.initials: S
authors.lastname: Gukovsky
authors.forename: S J
authors.initials: SJ
authors.lastname: Pandol
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000032:analysis / Q000037:antagonists & inhibitors*; D002458:Cell Fractionation; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000032:analysis / Q000378:metabolism*; D006873:Hydroquinones / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D010179:Pancreas / Q000166:cytology / Q000201:enzymology*; D010766:Phosphorylation; D051381:Rats; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D006873:Hydroquinones; D007211:Indoles; D019284:Thapsigargin; C018855:2-tert-butylhydroquinone; D006162:Guanylate Cyclase; D000252:Calcium-Transporting ATPases; D002118:Calcium; C000543:cyclopiazonic acid