Enhanced isradipine sensitivity in vascular smooth muscle cells due to hypoxia‐induced Cav1.2 splicing and RbFox1/Fox2 downregulation

• Published in: The FEBS journal 2024-10, Vol.291 (19), p.4265-4285
• Main Authors: Poore, Charlene Priscilla, Yang, Jialei, Wei, Shunhui, Fhu, Chee Kong, Bichler, Zoë, Wang, Juejin, Soong, Tuck Wah, Liao, Ping
• Format: Article
• Language: English
• Subjects: Alternative splicing; Calcium channel blockers; Calcium channels; Calcium channels (voltage-gated); Calcium influx; Cav1.2; Cell culture; Cerebral infarction; Channels; Down-regulation; Gene expression; Hypertension; Hypoxia; Ischemia; isradipine; Muscle contraction; Muscles; Myocardial infarction; Proteins; RbFox; RNA-binding protein; Smooth muscle
• ISSN: 1742-464X; 1742-4658; 1742-4658
• DOI: 10.1111/febs.17159

Calcium influx via the L‐type voltage‐gated Cav1.2 calcium channel in smooth muscle cells regulates vascular contraction. Calcium channel blockers (CCBs) are widely used to treat hypertension by inhibiting Cav1.2 channels. Using the vascular smooth muscle cell line, A7r5 and primary culture of cerebral vascular smooth muscle cells, we found that the expression and function of Cav1.2 channels are downregulated during hypoxia. Furthermore, hypoxia induces structural changes in Cav1.2 channels via alternative splicing. The expression of exon 9* is upregulated, whereas exon 33 is downregulated. Such structural alterations of Cav1.2 channels are caused by the decreased expression of RNA‐binding proteins RNA‐binding protein fox‐1 homolog 1 and 2 (RbFox1 and RbFox2). Overexpression of RbFox1 and RbFox2 prevents hypoxia‐induced exon 9* inclusion and exon 33 exclusion. Importantly, such structural alterations of the Cav1.2 channel partly contribute to the enhanced sensitivity of Cav1.2 to isradipine (a CCB) under hypoxia. Overexpression of RbFox1 and RbFox2 successfully reduces isradipine sensitivity in hypoxic smooth muscle cells. Our results suggest a new strategy to manage ischemic diseases such as stroke and myocardial infarction. L‐type voltage‐gated Cav1.2 calcium channel regulates smooth muscle vascular contraction through calcium influx. Hypoxia downregulates and induces Cav1.2 alternative splicing (upregulating exon 9* and downregulating exon 33) in vascular smooth muscle cells, mediated by reduced RbFox1/2 expression. Hypoxia‐induced Cav1.2 alternative splicing enhances sensitivity to calcium channel blocker, isradipine. RbFox1/2 overexpression during hypoxia prevents splicing changes and reduces isradipine sensitivity, suggesting a novel approach for managing ischemic diseases.