Abstract
Transient receptor potential melastatin channel subfamily member 2 (TRPM2) has an essential role in protecting cell viability through modulation of oxidative stress. TRPM2 is highly expressed in cancer. When TRPM2 is inhibited, mitochondria are dysfunctional, ROS levels are increased, and cell viability is reduced. Here, the importance of NF-E2-related factor (Nrf2) in TRPM2-mediated suppression of oxidant stress was explored. In TRPM2 depleted cells, antioxidant cofactors glutathione, NADPH, and NADH were significantly reduced. Cytoplasmic and nuclear expression of Nrf2 and of IQGAP1, a modulator of Nrf2 stability regulated by intracellular calcium, were decreased. Antioxidant enzymes transcriptionally regulated by Nrf2 and involved in GSH, NADPH, and NADH generation were significantly lower including PRX1 and PRX3, GPX4, GSTP1, GCLC, and MTHFD2. The glutamine pathway leading to GSH production was suppressed, and ATP and GTP levels were impaired. Reconstitution with wild type TRPM2 or Nrf2, but not TRPM2 pore mutant E960D, rescued expression of enzymes downstream of Nrf2 and restored GSH and GTP. Cell viability, ROS, NADPH, NADH, and ATP levels were fully rescued by TRPM2 and partially by Nrf2. These data show that TRPM2 maintains cell survival following oxidative stress through modulation of antioxidant pathways and cofactors regulated by Nrf2.
Highlights
TRPM2 belongs to the transient receptor potential (TRP) ion channel superfamily
Major findings are: (1) TRPM2 function is necessary to maintain GSH, NADPH, and NADH levels, and when TRPM2 is inhibited, these antioxidant cofactors are significantly reduced; (2) TRPM2 modulates Nrf[2] expression and that of downstream enzymes involved in GSH, NADPH, and NADH generation in protection from oxidative stress; (3) Nrf[2] regulatory proteins IQGAP1and Keap[1] are reduced in TRPM2 depleted cells; (4) in the TRPM2 knockout (KO), reduced expression of enzymes involved in generation of GSH and low levels of glutamine contribute to reduced GSH; and (5) reconstitution with TRPM2 completely restored cell viability, Nrf[2] expression, and GSH, NAD+/NADH, NADP+/NADPH, ATP, GTP, and glutamine levels, whereas the pore mutant E960D did not
High ROS levels are found in TRPM2 depleted neuroblastoma cells compared to controls[20,22], showing that maintenance of GSH and NADPH levels in these cells is critically important in regulating cytotoxicity
Summary
TRPM2 belongs to the transient receptor potential (TRP) ion channel superfamily. Members of this superfamily, the TRPM (Melastatin) subfamily, are involved in many fundamental cell functions including modulation of cell proliferation and survival[8,9,10]. Major findings are: (1) TRPM2 function is necessary to maintain GSH, NADPH, and NADH levels, and when TRPM2 is inhibited, these antioxidant cofactors are significantly reduced; (2) TRPM2 modulates Nrf[2] expression and that of downstream enzymes involved in GSH, NADPH, and NADH generation in protection from oxidative stress; (3) Nrf[2] regulatory proteins IQGAP1and Keap[1] are reduced in TRPM2 depleted cells; (4) in the TRPM2 knockout (KO), reduced expression of enzymes involved in generation of GSH and low levels of glutamine contribute to reduced GSH; and (5) reconstitution with TRPM2 completely restored cell viability, Nrf[2] expression, and GSH, NAD+/NADH, NADP+/NADPH, ATP, GTP, and glutamine levels, whereas the pore mutant E960D did not. Reconstitution with Nrf[2] fully restored GSH and GTP, partially restored cell viability, ATP, NADH, and NADPH, and significantly reduced ROS These studies demonstrate an important mechanism through which TRPM2 protects cell viability and modulates oxidative stress, through regulation of Nrf[2]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
