MAPK8 and obesity due to melanocortin 4 receptor deficiency: These demonstrated that ER stress markers including phospho-IRE1 (Serine/threonine-protein kinase/endoribonuclease IRE1) and phospho-JNK (Mitogen-activated protein kinase [c-Jun N-terminal kinase]) increased in BAT in mice with obesity (Fig. 4G,H).