Nesfatin-1 Suppresses Cardiac L-type Ca2+ Channels Through Melanocortin Type 4 Receptor and the Novel Protein Kinase C Theta Isoform Pathway

Abstract

Background/Aims: Nesfatin-1 (NF-1), an anorexic nucleobindin-2 (NUCB2)-derived hypothalamic peptide, acts as a peripheral cardiac modulator and it can induce negative inotropic effects. However, the mechanisms underlying these effects in cardiomyocytes remain unclear. Methods: Using patch clamp, protein kinase assays, and western blot analysis, we studied the effect of NF-1 on L-type Ca²⁺ currents (I_Ca,L) and to explore the regulatory mechanisms of this effect in adult ventricular myocytes. Results: NF-1 reversibly decreased I_Ca,L in a dose-dependent manner. This effect was mediated by melanocortin 4 receptor (MC4-R) and was associated with a hyperpolarizing shift in the voltage-dependence of inactivation. Dialysis of cells with GDP-β-S or anti-G_β antibody as well as pertussis toxin pretreatment abolished the inhibitory effects of NF-1 on I_Ca,L. Protein kinase C (PKC) antagonists abolished NF-1-induced responses, whereas inhibition of PKA activity or intracellular application of the fast Ca²⁺-chelator BAPTA elicited no such effects. Application of NF-1 increased membrane abundance of PKC theta isoform (PKC_θ), and PKC_θ inhibition abolished the decrease in I_Ca,L induced by NF-1. Conclusion: These data suggest that NF-1 suppresses L-type Ca²⁺ channels via the MC4-R that couples sequentially to the βγ subunits of G_i/o-protein and the novel PKC_θ isoform in adult ventricular myocytes.