title: Constitutive NO synthase regulates the Na+/Ca2+ exchanger in human T cells: role of [Ca2+]i and tyrosine phosphorylation.
abstract: For many types of cells, heat stress leads to an increase in intracellular free calcium concentration ([Ca2+](i)) that has been shown to trigger a wide variety of cellular responses. In T lymphocytes, for example, heat stress stimulates pathways that make them more susceptible to Fas/CD95-mediated apoptosis. Because of our interest in understanding more about the response of lymphocytes to various stressors, we used human peripheral and Jurkat T lymphocytes to investigate the effect of heat stress on calcium homeostasis. We found that peripheral and Jurkat T cells both exhibit cNOs activity but not iNOs activity. Heat stress increased NO production, which was inhibited by LNNA (a cNOs inhibitor) but not L-NIL (an iNOs inhibitor). Heat stress increased [Ca2+](i) in Jurkat T cells by decreasing the K(m) of the cell surface membrane Na+/Ca2+ exchanger for extracellular Ca2+. Heating also increased cNOs phosphorylation at tyrosine residues. In cells incubated with LNNA, heat stress promoted an increase in [Ca2+](i) and a decrease in [Na+](i) greater than in cells heated without LNNA, a larger decrease in K(m) of the Na+/Ca2+ exchanger for extracellular Ca2+, and decreased phosphorylation of cNOs. Our results suggest that cNOs plays an important regulatory role after heat stress. Heating appears to increase the phosphorylation of cNOs that is complexed with the Na+/Ca2+ exchanger to decrease its activity. This process is related to increased expression of Fas/CD95 on the cell surface, which might explain the apoptotic diathesis of lymphocytes after heat stress.
authors.affiliation: Department of Cellular Injury, Walter Reed Army Institute of Research, 503 Robert Grant Avenue, Room 1N07, Silver Spring, MD 20910-7500, USA. Juliann.Kiang@na.amedd.army.mil
authors.forename: Juliann G
authors.initials: JG
authors.lastname: Kiang
authors.forename: David E
authors.initials: DE
authors.lastname: McClain
authors.forename: Vishal G
authors.initials: VG
authors.lastname: Warke
authors.forename: Sandeep
authors.initials: S
authors.lastname: Krishnan
authors.forename: George C
authors.initials: GC
authors.lastname: Tsokos
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018882:Heat Stress Disorders / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D007700:Kinetics; D008239:Lysine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019335:Nitroarginine / Q000494:pharmacology; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D010766:Phosphorylation; D011233:Precipitin Tests; D012964:Sodium / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D013601:T-Lymphocytes / Q000201:enzymology / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*; D019014:fas Receptor / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; C090663:N(6)-(1-iminoethyl)lysine; C110881:S-nitro-N-acetylpenicillamine; D019831:Sodium-Calcium Exchanger; D019014:fas Receptor; C013407:benzamil; D019335:Nitroarginine; D009569:Nitric Oxide; D014443:Tyrosine; D000584:Amiloride; D012964:Sodium; D019001:Nitric Oxide Synthase; D010396:Penicillamine; D008239:Lysine; D002118:Calcium