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

Abstract

Interferon-γ (IFN-γ) ± tumor necrosis factor-α (TNF-α) induces antiproliferation and intracellular Ca2+ 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-γ-induced intracellular Ca2+store depletion. There was a time-dependent decrease in thapsigargin-dependent internal Ca2+ release after exposure of the cells to the cytokines. The intracellular Ca2+ pump [sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA)] protein in lysates and membranes of cells treated with IFN-γ ± TNF-α, but not with TNF-α 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 Ca2+ 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-γ-induced decrease in the level of SERCA accounts for the depleted state of internal Ca2+stores in cytokine-treated HSG cells. These data suggest a novel mechanism for the inhibition of HSG cell growth by IFN-γ.