PDK4 and obesity due to melanocortin 4 receptor deficiency: Pyruvate dehydrogenase kinase 4 (PDK4) directly interacts with and stabilizes the IP3R1-GRP75-VDAC1 complex at the MAM interface, and obesity-induced increases in PDK4 activity augment the MAM formation and Ca2+ flux to the mitochondria (Thoudam et al., 2019).