RACK1 and Alzheimer disease: Receptors for activated C kinase 1 (RACK1) is reported to directly interact with the M1 mAChR (Borroto-Escuela et al., 2011a), and the expression of RACK1 is also decreased in the cortex of Alzheimer's disease post-mortem brain tissues compared to healthy aged brain tissues (Battaini et al., 1999).