Differential effects of two-pore channel protein 1 and 2 silencing in MDA-MB-468 breast cancer cells

Abstract

Two-pore channel proteins, TPC1 and TPC2, are calcium permeable ion channels found localized to the membranes of endolysosomal calcium stores. There is increasing interest in the role of TPC-mediated intracellular signaling in various pathologies; however their role in breast cancer has not been extensively evaluated. TPC1 and TPC2 mRNA was present in all non-tumorigenic and tumorigenic breast cell lines assessed. Silencing of TPC2 but not TPC1 attenuated epidermal growth factor-induced vimentin expression in MDA-MB-468 breast cancer cells. This effect was not due to a general inhibition of epithelial to mesenchymal transition (EMT) as TPC2 silencing had no effect on epidermal growth factor (EGF)-induced changes on E-cadherin expression. TPC1 and TPC2 were also shown to differentially regulate cyclopiazonic acid (CPA)-mediated changes in cytosolic free Ca 2+ . These findings indicate potential differential regulation of signaling processes by TPC1 and TPC2 in breast cancer cells. Abbreviations

Sodium homeostasis in the tumour microenvironment

“…Proteins forming the G proteincoupled receptor-activated Na + leak channel (NALCN) have been suggested as potential cancer susceptibility loci (63), and although evidence for its involvement in cancer is limited, NALCN may provide an additional route for Na + influx, thus elevating [Na + ]i. Finally, the two-pore channel (TPC) family of lysosomal and endosomal cation channels can increase cytosolic Ca 2+ and Na + and have been shown to promote lung cancer cell migration (64) and epithelial-mesenchymal transition of breast cancer cells (65).…”

Endolysosomal Ca2+ Signalling and Cancer Hallmarks: Two-Pore Channels on the Move, TRPML1 Lags Behind!

“…Subsequently, it was found that TPC1 and TPC2 transcripts were similarly expressed in a different set of human breast cancer cells, although only genetic silencing of TPC2 inhibited EGF-induced vimentin, but not E-cadherin, expression in the highly aggressive MDA-MB-468 cell line. On the other hand, silencing of either TPC isoform did not affect the rate of cell proliferation [210]. TPC2 silencing reduced the amount of Ca 2+ released upon pharmacological depletion of the ER under 0 Ca 2+ conditions and the amplitude of SOCE recorded upon restoration of extracellular Ca 2+ levels [210].…”

Roles of NAD+ and Its Metabolites Regulated Calcium Channels in Cancer

“…For example, NAADP-evoked Ca 2+ signals through TPC1 and TPC2 sustained glutamate-induced autophagy in SHSY5Y neuroblastoma cells [ 110 ]. Silencing of TPC2 attenuated epidermal growth factor-induced vimentin expression in MDA-MB-468 breast cancer cells [ 111 ]. TPC2 overexpression in 4T1 mouse breast cancer cell lines and human HeLa cervical cancer cell lines inhibited the fusion of autophagosomes and lysosomes, causing the accumulation of autophagosomes [ 112 ].…”