AKAP9 mutations contribute to long QT syndrome by disrupting the macromolecular complex required for β-adrenergic modulation of potassium channels.
Inherited long QT syndrome (LQTS) is a life-threatening cardiac channelopathy characterized by impaired ventricular repolarization and heightened susceptibility to ventricular arrhythmias and sudden cardiac death. While mutations in ion channel genes (e.g., KCNQ1, KCNH2) are well-known causes of LQTS, emerging evidence highlights the critical role of regulatory proteins, including a-kinase anchoring protein 9 (AKAP9), in modulating channel function. AKAP9 scaffolds protein kinase A (PKA), protein phosphatase 1 (PP1), and phosphodiesterase PDE4D3 into a macromolecular complex with KCNQ1, enabling dynamic phosphorylation of the potassium channels in response to β-adrenergic stimulation. Mutations in AKAP9 gene (e.g., S1570L) or its binding partner KCNQ1 (e.g., G589D) destabilize this complex, impairing PKA-mediated phosphorylation of KCNQ1 at serine-27. This defect blunts the sympathetic enhancement of slow delayed rectifier potassium channel (I
Yuan et al. (Thu,) studied this question.