Interferon-gamma induces a decrease in the intracellular calcium pump in a human salivary gland cell line

Secretory Physiology Section, Gene Therapy and Therapeutics Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892 Interferon- (IFN- ) ± tumor necrosis factor- (TNF- ) induces antiproliferation and intracellular Ca 2+ store depletion in a human submandibular ductal cell line (HSG), which can be reversed on cytokine removal [A. J. Wu, G. C. Chen, B. J. Baum, and I. S. Ambudkar. Am. J. Physiol. 270 ( Cell Physiol. 39): C514-C521, 1996]. Here we have examined a possible mechanism for the IFN- -induced intracellular Ca 2+ store depletion. There was a time-dependent decrease in thapsigargin-dependent internal Ca 2+ release after exposure of the cells to the cytokines. The intracellular Ca 2+ pump [sarco(endo)plasmic reticulum Ca 2+ -ATPase (SERCA)] protein in lysates and membranes of cells treated with IFN- ± TNF- , but not with TNF- alone, showed a similar time-dependent decrease (examined using a SERCA2 antibody). Removal of the cytokines, which resulted in recovery of cell growth and refill of internal Ca 2+ stores, also increased the level of SERCA protein. The decrease in SERCA is not a result of decreased cell proliferation, since thapsigargin, 2,5-di-( t -butyl)-1,4-hydroquinone, or serum-free growth conditions induced antiproliferative effects on HSG cells without any corresponding decrease in SERCA. We suggest that the IFN- -induced decrease in the level of SERCA accounts for the depleted state of internal Ca 2+ stores in cytokine-treated HSG cells. These data suggest a novel mechanism for the inhibition of HSG cell growth by IFN- . sarco(endo)plasmic reticulum calcium adenosinetriphosphatase protein; intracellular calcium ion store; salivary cell line; cell proliferation