RAP2A can also activate atypical MAPKs, such as TNIK, MINK, and MAP4K4, stimulating JNK and other downstream kinases (61–64), suggesting that RAP2A may have functions beyond desensitization of the β3-AR in healthy adipocytes and in the context of obesity. Here, MAPK8 is linked to obesity due to melanocortin 4 receptor deficiency.