TMEM97 and early-onset autosomal dominant Alzheimer disease: Sigma receptors (σRs) are regulatoryproteins involved invarious homeostatic processes, including the modulation of ion channels, regulation of cellular cholesterol levels, and control of cell proliferation and apoptosis. This receptor family comprises of two geneticallyunrelated subtypes: the sigma-1 receptor (σ1R) andthe sigma-2 receptor (σ2R). The σ2R, in particular, has attracted increasingattention for its role in cholesterol metabolism, its overexpressionin cancer cells, and its potential asa therapeutic target in Alzheimer’s disease.