RBM20 Regulates CaV1.2 Surface Expression by Promoting Exon 9* Inclusion of CACNA1C in Neonatal Rat Cardiomyocytes

Area of Science:

• Molecular Biology
• Cardiovascular Research
• Gene Regulation

Background:

• The CACNA1C gene encodes the CaV1.2 protein, a key component of cardiac l-type calcium channels.
• Alternative splicing of CACNA1C generates diverse CaV1.2 isoforms with varying electrophysiological properties.
• Mechanisms governing CACNA1C alternative splicing, particularly during cardiac development and disease, are not fully understood.

Purpose of the Study:

• To investigate the role of RNA-binding protein motif 20 (RBM20) in regulating CACNA1C alternative splicing.
• To determine the functional consequences of RBM20-mediated splicing on CaV1.2 channels in cardiomyocytes.

Main Methods:

• RNA sequencing analysis to identify potential RBM20 targets.
• Overexpression and siRNA knockdown of RBM20 in neonatal rat cardiomyocytes (NRCMs).
• RNA immunoprecipitation to assess RBM20 binding sites.
• Electrophysiological recordings to measure l-type calcium currents.
• Assessment of CaV1.2 membrane surface expression.

Main Results:

• RBM20 overexpression promoted the inclusion of CACNA1C exon 9* in NRCMs.
• RBM20 knockdown led to the skipping of exon 9*.
• RBM20 specifically targeted introns flanking exon 9*, without affecting other alternative exons.
• RBM20 overexpression decreased, while knockdown increased, l-type calcium currents.
• RBM20 overexpression reduced CaV1.2 membrane surface expression.

Conclusions:

• RBM20 specifically regulates CACNA1C alternative splicing by controlling the inclusion of exon 9*.
• This RBM20-mediated splicing event impacts CaV1.2 channel function and cell-surface expression in cardiomyocytes.
• RBM20 plays a significant role in modulating cardiac calcium channel activity through alternative splicing.