Stress-activated map kinase-interacting protein 1 (Sin1) is highly similar to the yeast stress- activated protein kinase SIN1. Sin1 is an essential mTORC2 subunit that is required to act as the PDK2 that phosphorylates Akt/PKB at Ser 473. Sin1 has been implicated as a scaffolding protein. Sin1 is required for rictor binding in the mTORC2 complex. Sin1 has also been shown to be important to the SAPK (stress-activated kinase) signaling pathway and in the nucleus may act as a scaffold between ATF-2 and p38 to facilitate p38-induced phosphorylation of ATF-2. Sin1 is also found to form a complex with c-Jun N-terminal kinase (JNK) and may similarly function as a scaffolding protein in JNK signaling.