APP and early-onset autosomal dominant Alzheimer disease: The proteolytic activity of BACE1 promotes the generation of β-amyloid (Aβ) peptides from amyloid precursor protein in Alzheimer’s disease.86 BACE1 expression can be activated by muscarinic acetylcholine receptor M1/M3 via PKC and MAP kinase signaling cascades.87 BACE1 activity is modulated by other GPCRs, such as the A2A and delta-opioid receptors.33 It has been shown that selective activation of the M2 receptor will suppress BACE1 expression via PKA-mediated signaling events.33