RSK 90 kDa ribosomal S6 kinase A family of 90 kDa ribosomal S6 kinases (RSK; also known as p90rsk or MAPK-activated protein kinase-1, MAPKAP-K1). The RSK family of kinases includes three isoforms: RSK1, RSK2 and RSK3 that are encoded by distinct genes and show 75-80% amino acid identity. RSK proteins is regulated by the ERK kinase pathway. GO:0004711 IMR:0000248 MAPK-activated protein kinase-1 MAPKAP kinase-1 MAPKAP-K1 molecule_role p90rsk S6K MAPKAPK