PhD Scientific Days 2025

Molecular Medicine IV.

Molecular Characterization of Pathological TRPM2 Cation Channel Variants

Name of the presenter

Tóth Ádám

Institute/workplace of the presenter

Department of Biochemistry, Semmelweis University, Budapest, Hungary

Authors

Ádám Tóth¹

1: Department of Biochemistry, Semmelweis University, Budapest, Hungary

Text of the abstract

The Ca2+-permeable cation channel TRPM2 gained traction due to its exceedingly high temperature sensitivity. Accordingly, physiological studies have found that KO mice possess impaired temperature homeostasis. The central heat adjustment is restricted to the hypothalamic preoptic area, where TRPM2-expressing neurons were identified. Besides heat sensitivity, this ion channel has widespread physiological roles, such as cytokine production, apoptosis, and oxidative stress response. Moreover, genetic association studies have found linkage between single-nucleotide variations in TRPM2 and bipolar disorder (D543E, R755C) or amyotrophic lateral sclerosis and Parkinson's dementia (P1018L).
Investigation of these channel variants lags behind. Thus, we aim to examine them in an experimental arrangement where the essential intracellular agents (adenosine diphosphate ribose (ADPR), Ca2+, and phosphatidylinositol 4,5-bisphosphate (PIP2)) can be monitored to better understand their role in pathophysiology.
The TRPM2 variants are transiently expressed in HEK-293 cells. Functional measurements are performed in a cell-free environment using the inside-out patch clamp configuration, enabling the reliable quantification of gating parameters, ligand sensitivity, and temperature dependence.
Functional studies showed no difference in ligand sensitivity in R755C and P1018L compared to wild-type channels. Interestingly, D543E variant has increased agonist sensitivity at cold, room, and physiological temperatures. Recording open channel probabilities under these conditions revealed shallower temperature dependence of the gating parameters. Due to its increased apparent affinities, this variant has more pronounced activity at physiological concentration and temperature ranges than wild-type channels.
Here we provide evidence that the D543E variant has a gain-of-function phenotype. Considering its neuronal expression, it possibly increases neuronal excitability, which may explain its role in the etiology of bipolar disorder.
This work is funded by the Hungarian Centre of Excellence for Molecular Medicine (H-CEMM), National Research, Development and Innovation Fund NKFIH KKP_22 grant (144199) and ADVANCED (149640), HUN-REN Office for Supported Research Groups, SE 250+ Excellence PhD Scholarship and University Research Scholarship Programme 2024 (EKÖP-2024-146).