PhD Scientific Days 2024

Poster Session E - Molecular Medicine 2.

Molecular Characterization of Pathological TRPM2 Cation Channel Variants

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 the heat sensitivity, this ion channel has widespread physiological roles, such as cytokine production, apoptosis or oxidative stress response.. Moreover, genetic association studies have found linkage between point mutations 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 in order 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 inside-out patch clamp configuration. This method enables the recording of micro- and macroscopic currents, as well as the efficient exchange of intracellular ligands. With this method, the ligand sensitivity, gating parameters, inactivation kinetics, and temperature dependence of individual channel variants can be accurately defined.
Functional studies showed no difference neither in inactivation, nor in ligand senstivity in R755C and P1018L compared to wild-type channels. Interestingly, D543E mutation resulted in increased Ca2+-sensitivity at room temperature and this difference is even higher at elevated temperature (37°C) while leaving the ADPR-sensitivity intact.
Single channel analysis (unitary conductance, open probability, permeability) at different temperatures might reveal the phenomenon behind the increased Ca2+-sensitivity of D543E. Further examination in vivo is required to understand how this altered functionality contributes to the complex etiology of bipolar disorder.
This work is funded by Hungarian Centre of Excellence for Molecular Medicine (H-CEMM), János Bolyai Research Scholarship of the Hungarian Academy of Sciences (BO/00103/20), HUN-REN Office for Supported Research Groups and SE 250+ Excellence PhD Scholarship.