Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Poster Abstracts

18-POS Board 18 Dissecting a High-affinity Binding Region for T-type Calcium Channels Antagonists. Eduardo Chavez-Colorado , Uriel J. Vazquez-Ayala, Zazil Herrera-Carrillo, Juan C. Gomora. Instituto de Fisiología Celular-UNAM, Mexico City, Cd Mx, Mexico. T-type calcium or Ca V 3 channels are involved in several crucial cell functions. Remarkably, Ca V 3 channels are implicated in pathophysiological processes such as epilepsy, sleep disorders, hypertension, neuropathic pain and cancer. However, the lack of potent and selective antagonists of Ca V 3 channels has been a setback for further investigation of these channels function in neurological diseases and to validate them as efficient drug targets. Recently, a series of potent and selective T-type calcium channel blockers (T-Type Antagonists or TTAs) have been reported in several studies. Here, we have gain insights into the binding site for the molecular coupling of TTA-A2 ([2-(4-cyclopropylphenyl)-N-((1R)-1-{5-[(2,2,2-trifluoroethyl)oxo]pyridin-2- yl}ethyl)acetamide]) on the human Ca V 3.1 T-type calcium channel. By combining molecular simulations, mutagenesis and patch-clamp experiments on Ca V 3.1 channels expressed in HEK- 293 cells, we have collected experimental evidence about the molecular basis of TTA-A2 binding site in this channel. The binding site is mainly outlined by amino acid residues from S6 segments of Domain I and IV. We also confirmed that the binding site is conserved in the three human Ca V 3 channels, but not in the L-type channels, as suggested by sequence alignments. In addition, we report the existence of a high affinity binding region for other structural and functional diverse TTAs (e.g., mibefradil, TTA-P2, penfluridol, etc.); and furthermore, we provide evidence that TTA-Q4, a positive allosteric modulator of TTA-A2 blocking effect, does not share the same binding site with the latter. Our results contribute to the knowledge for the rational design of T-type channel antagonists based on the structure of the TTA-A2 binding site, and might represent a breakthrough for understanding the kind of physical interaction that allow these compounds to modulate differentially the T-type calcium channels subfamily.

Supported by CONACYT-MEXICO 167790 and PAPIIT-UNAM IN207614.

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