Effect of gamma-secretase inhibitors on muscarinic receptor-mediated calcium signaling in human salivary epithelial cells.
Altered intracellular Ca(2+) signaling has been observed in cells derived from Alzheimer's disease patients, and a possible link between gamma-secretase activity and the content of intracellular Ca(2+) stores has been suggested. To test this hypothesis we studied the effects of several gamma-secretase inhibitors on muscarinic receptor-mediated intracellular calcium release in the human salivary gland cell line HSG. Although several inhibitors in the peptide aldehyde class partially blocked carbachol-induced Ca(2+) transients, these effects did not appear to be due to gamma-secretase inhibition, and overall we found no evidence that inhibition of gamma-secretase activity had any significant effect on agonist-induced intracellular calcium release in HSG cells. In complementary experiments with presenilin-null cells we found that the reconstitution of gamma-secretase activity by transfection with wild-type presenilin 1 likewise had no significant effect on thapsigargin-induced Ca(2+) release. In a test of the specific hypothesis that the level of APP intracellular domain (AICD), the intracellular fragment of the beta-amyloid precursor protein (APP) resulting from gamma-secretase cleavage, can modulate the Ca(2+) content of the endoplasmic reticulum, we were unable to demonstrate any effect of APP small interfering RNA on the magnitude of carbachol-induced intracellular calcium release in HSG cells. Together our data cast considerable doubt on the hypothesis that there is a direct link between gamma-secretase activity and the content of intracellular Ca(2+) stores.
Membrane Biology Section, Gene Therapy and Therapeutics Branch, National Institute of Dental and Craniofacial Research, Bldg 10, Rm. 1A01, GTTB, Bethesda, MD 20892, USA.
Young S
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D053829:Amyloid Precursor Protein Secretases; D000818:Animals; D016282:Aspartic Acid Endopeptidases; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D002461:Cell Line, Transformed; D010450:Endopeptidases / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D011480:Protease Inhibitors / Q000494:pharmacology*; D011976:Receptors, Muscarinic / Q000378:metabolism*; D012469:Salivary Glands / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*
D011480:Protease Inhibitors; D011976:Receptors, Muscarinic; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; C509282:Bace1 protein, mouse; D002118:Calcium