Understanding the involvement of sphingosine kinase-1 and two-pore channels in calcium signaling in T cells.

Abstract

Abstract Calcium (Ca 2+) signaling is an essential requirement for cell activation, proliferation, differentiation, homeostasis, etc. In the tumor microenvironment, however, an upregulation of the Ca 2+signaling pathway has been associated with cancer cell proliferation and malignancy, which further contributes to immune response suppression. Although nicotinic acid adenine dinucleotide phosphate (NAADP) is the most potent Ca 2+signaling secondary messenger known, the NAADP-Ca 2+signaling pathway remains elusive and controversial. Studies have so far revealed the interaction of NAADP with accessory proteins such as Jupiter microtubule-associated homolog 2 (JPT2) and Lsm12 along with the poorly characterized ‘two-pore channels’ (TPC1 and TPC2) located in the acidic endo-lysosomal compartments of cells. In 2018, a screening campaign revealed the ability of PF-543 to inhibit NAADP-mediated Ca 2+signals in sea urchin egg homogenates and in human U2OS cells. As PF-543 is marketed as a potent sphingosine kinase 1 (SphK-1) inhibitor and is believed to possess TPC inhibitory function, the mechanism behind PF-543’s ability to inhibit NAADP-mediated Ca 2+signals (through inhibition of SphK-1 or the TPCs, or both) needed investigation. Therefore, we tested structural analogs of PF-543 and evaluated their ability to inhibit both SpK-1 and Ca 2+signals in DO.11.10 cells, a T cell hybridoma that possesses the T cell receptor (TCR). Thus, in addition to identifying novel targets for the development of Ca 2+signaling modulators and anticancer therapeutics, our results also reveal the contributions of SphK-1 and the TPCs in the NAADP-mediated Ca 2+signaling pathway in T cells. NIH R15GM131329