AKT1 and Huntington disease: Phosphorylation of polyQ-expanded HTT at S421 within the Akt consensus site RXRXXS by Akt and serum- and glucocorticoid-induced kinase (SGK) reduces inclusion formation and neurotoxicity in HD (Humbert et al., 2002; Rangone et al., 2004), and is negatively regulated by the protein phosphatase, calcineurin (Pardo et al., 2006).