부산대학교 도서관

The sodium leak channel NALCN is a key player in establishing the resting membrane potential (RMP) in neurons andtransduces changes in extracellular Ca2+ concentration ([Ca2+]e) into increased neuronal excitability as thedownstream effector of calcium-sensing receptor (CaSR). Gain-of-function mutations in the human NALCN gene causeencephalopathy and severe intellectual disability. Thus, understanding the regulatory mechanisms of NALCN isimportant for both basic and translational research. This study reveals a novel mechanism for NALCN regulation byarginine methylation. Hippocampal dentate granule cells in protein arginine methyltransferase 7 (PRMT7)-deficientmice display a depolarization of the RMP, decreased threshold currents, and increased excitability compared to wildtypeneurons. Electrophysiological studies combined with molecular analysis indicate that enhanced NALCN activitiescontribute to hyperexcitability in PRMT7−/− neurons. PRMT7 depletion in HEK293T cells increases NALCN activity byshifting the dose-response curve of NALCN inhibition by [Ca2+]e without affecting NALCN protein levels. In vitromethylation studies show that PRMT7 methylates a highly conserved Arg1653 of the NALCN gene located in thecarboxy-terminal region that is implicated in CaSR-mediated regulation. A kinase-specific phosphorylation siteprediction program shows that the adjacent Ser1652 is a potential phosphorylation site. Consistently, our data fromsite-specific mutants and PKC inhibitors suggest that Arg1653 methylation might modulate Ser1652 phosphorylationmediated by CaSR/PKC-delta, leading to [Ca2+]e-mediated NALCN suppression. Collectively, these data suggest thatPRMT7 deficiency decreases NALCN methylation at Arg1653, which, in turn, decreases CaSR/PKC-mediated Ser1652phosphorylation, lifting NALCN inhibition, thereby enhancing neuronal excitability. Thus, PRMT7-mediated NALCNinhibition provides a potential target for the development of therapeutic tools for neurological diseases.