Role of TRPM2 in cell proliferation and susceptibility to oxidative stress

Abstract

The transient receptor potential (TRP) channel TRPM2 is an ion channel that modulates cell survival. We report here that full-length (TRPM2-L) and short (TRPM2-S) isoform expression was significantly increased in human neuroblastoma compared with adrenal gland. To differentiate the roles of TRPM2-L and TRPM2-S in cell proliferation and survival, we established neuroblastoma SH-SY5Y cell lines stably expressing either TRPM2 isoform or empty vector. Cells expressing TRPM2-S showed significantly enhanced proliferation, downregulation of phosphatase and tensin homolog (PTEN), and increased protein kinase B (Akt) phosphorylation and cell surface glucose transporter 1 (Glut1) compared with cells expressing TRPM2-L or empty vector. ERK phosphorylation was increased, and forkhead box O 3a (FOXO3a) levels were decreased. Inhibitor studies demonstrated that enhanced proliferation was dependent on phosphatidylinositol 3-kinase/Akt, ERK, and NADPH oxidase activation. On the other hand, TRPM2-S-expressing cells were significantly more susceptible to cell death induced by low H2O2 concentrations (50-100 μM), whereas TRPM2-L-expressing cells were protected. This was associated with a significant increase in FOXO3a, MnSOD (SOD2), and membrane Glut1 in TRPM2-L-expressing cells compared with TRPM2-S expressing cells. We conclude that TRPM2 channels occupy a key role in cell proliferation and survival following oxidative stress in neuroblastoma. Our results suggest that overexpression of TRPM2-S results in increased proliferation through phosphatidylinositol 3-kinase/Akt and ERK pathways, while overexpression of TRPM2-L confers protection against oxidative stress-induced cell death through FOXO3a and SOD. TRPM2 channels may represent a novel future therapeutic target in diseases involving oxidative stress.

Depletion of the Human Ion Channel TRPM2 in Neuroblastoma Demonstrates Its Key Role in Cell Survival through Modulation of Mitochondrial Reactive Oxygen Species and Bioenergetics

“…The decreased proliferation of untreated SK-N-DZ and SK-N-FI cells expressing TRPM2-S (Fig. 11A) may be due to reduced calcium influx leading to lower levels of mitochondrial proteins including HIF-1/2␣ and mitochondrial function, as shown for SH-SY5Y cells expressing TRPM2-S (40,41).…”

“…TRPM2 has an important role in cell survival following oxidative stress or ischemic injury (35)(36)(37)40). Recent studies have shown that TRPM2 is highly expressed in a number of malignancies including melanoma, lung, neuroblastoma, and breast cancer (39,41,42), suggesting that it plays a role in promoting tumor growth, and that inhibition may be a novel therapeutic approach.…”

“…TRPM2 channels are highly expressed in a number of cancers including melanoma (39), breast cancer, 4 and neuroblastoma (40 -42). Previously, TRPM2 function has been studied in cancer cells with either shRNA down-regulation or expression of the dominant-negative TRPM2-S (40,41). TRPM2-L protected neuroblastoma SH-SY5Y cells from physiological oxidative stress through increased levels of Forkhead box transcription factor 3a (FOXO3a) and superoxide dismutase 2 (SOD2, MnSOD) (40), whereas cells expressing the dominant-negative TRPM2-S isoform had reduced FOXO3a and SOD2 levels and enhanced ROS, increasing susceptibility to oxidant injury.…”

“…Previously, TRPM2 function has been studied in cancer cells with either shRNA down-regulation or expression of the dominant-negative TRPM2-S (40,41). TRPM2-L protected neuroblastoma SH-SY5Y cells from physiological oxidative stress through increased levels of Forkhead box transcription factor 3a (FOXO3a) and superoxide dismutase 2 (SOD2, MnSOD) (40), whereas cells expressing the dominant-negative TRPM2-S isoform had reduced FOXO3a and SOD2 levels and enhanced ROS, increasing susceptibility to oxidant injury. Tumor growth was diminished by expression of dominant-negative TRPM2-S in a xenograft model, and the mechanisms involved reduced HIF-1/2␣ expression and mitochondrial function (41).…”

FoxO3a and disease progression

“…It becomes clear that increases in cellular ROS levels are known to be associated with aging [70][71][72][73][74][75] . Increased cellular oxidative stress regulates FoxO post-translational modifications and the activation of the FoxO family has been shown to regulate cellular oxidative-stress resistance [76][77][78][79][80][81] . Interestingly, to support these findings, recent studies suggest a possibility that Sirt3 and FoxO3a have been linked to an extended life span in humans [75][76][77][78]82] .…”