NLRP3 and cryopyrin-associated periodic syndrome: Protein kinase A (PKA) has been found to negatively regulate NLRP3 activation by phosphorylation at Ser295 (Ser291 in mouse models) in the NACHT domain; which is the site for cryo-pyrin-associated periodic syndromes (CAPS)-associated NLRP3 mutations [60], via TGR5-cAMP-PKA axis [61] and prostaglandin E2 receptor E-prostanoid 4 (EP4) axis [62].