Stabilization of negative activation voltages of Cav1.3 L-Type Ca²⁺-channels by alternative splicing

ABSTRACT

-->Low voltage-activated Cav1.3 L-type Ca²⁺-channels are key regulators of neuronal excitability controlling neuronal development and different types of learning and memory. Their physiological functions are enabled by their negative activation voltage-range, which allows Cav1.3 to be active at subthreshold voltages. Alternative splicing in the C-terminus of their pore-forming α1-subunits gives rise to C-terminal long (Cav1.3_L) and short (Cav1.3_S) splice variants allowing Cav1.3_S to activate at even more negative voltages than Cav1.3_L. We discovered that inclusion of exons 8b, 11, and 32 in Cav1.3_S further shifts activation (-3 to -4 mV) and inactivation (-4 to -6 mV) to more negative voltages as revealed by functional characterization in tsA-201 cells. We found transcripts of these exons in mouse chromaffin cells, the cochlea, and the brain. Our data further suggest that Cav1.3-containing exons 11 and 32 constitute a significant part of native channels in the brain. We therefore investigated the effect of these splice variants on human disease variants. Splicing did not prevent the gating defects of the previously reported human pathogenic variant S652L, which further shifted the voltage-dependence of activation of exon 11-containing channels by more than -12 mV. In contrast, we found no evidence for gating changes of the CACNA1D missense variant R498L, located in exon 11, which has recently been identified in a patient with an epileptic syndrome.

Our data demonstrate that alternative splicing outside the C-terminus involving exons 11 and 32 contributes to channel fine-tuning by stabilizing negative activation and inactivation gating properties of wild-type and mutant Cav1.3 channels.

KEYWORDS:

• Cav1.3
• Ca²⁺ channels
• L-type
• alternative splicing
• disease genetics

Acknowledgments

This work was supported by the Austrian Science Fund (FWF P27809, CavX/Doc-30-B30, MCBO/W1101). We thank Dr. Nadine J. Ortner for helpful advice and support during this  study.

Disclosure statement

The authors report no conflict of interest.

Data availability statement

The data that support the findings of this study are available from the corresponding author, upon reasonable request.

Supplementary Material

Supplemental data for this article can be accessed here.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.