Enhanced isradipine sensitivity in vascular smooth muscle cells due to hypoxia-induced Ca_v1.2 splicing and...

Area of Science:

• Cardiovascular Biology
• Molecular Biology
• Pharmacology

Background:

• L-type voltage-gated calcium channels (Ca_v1.2) regulate vascular smooth muscle contraction.
• Calcium channel blockers (CCBs) are primary treatments for hypertension.
• Understanding Ca_v1.2 regulation under hypoxia is crucial for treating ischemic diseases.

Purpose of the Study:

• To investigate the impact of hypoxia on Ca_v1.2 channel expression and function in vascular smooth muscle cells.
• To elucidate the molecular mechanisms underlying hypoxia-induced Ca_v1.2 channel alterations.
• To explore the therapeutic potential of modulating Ca_v1.2 channel structure for ischemic diseases.

Main Methods:

• Utilized A7r5 cell line and primary cerebral vascular smooth muscle cells.
• Analyzed Ca_v1.2 channel expression, function, and alternative splicing under hypoxic conditions.
• Investigated the role of RNA-binding proteins RbFox1 and RbFox2 in regulating Ca_v1.2 splicing.
• Assessed the effect of RbFox1/2 overexpression on Ca_v1.2 channel sensitivity to isradipine.

Main Results:

• Hypoxia downregulates Ca_v1.2 channel expression and function.
• Hypoxia induces alternative splicing of Ca_v1.2, increasing exon 9* and decreasing exon 33 inclusion.
• Decreased expression of RbFox1 and RbFox2 mediates these splicing changes.
• Structural alterations enhance Ca_v1.2 sensitivity to isradipine under hypoxia.
• RbFox1/2 overexpression reverses hypoxia-induced splicing changes and reduces isradipine sensitivity.

Conclusions:

• Hypoxia-induced structural changes in Ca_v1.2 channels contribute to altered drug sensitivity.
• RbFox1 and RbFox2 play critical roles in regulating Ca_v1.2 splicing under hypoxia.
• Modulating RbFox1/2 offers a novel therapeutic strategy for managing ischemic conditions like stroke and myocardial infarction.