Sigma 2 Receptor

Sigma-2 receptor (σ₂R), identified as TMEM97, is an endoplasmic-reticulum transmembrane protein linked to cancer biology, NPC1 interaction, and sterol-related regulation^[1]. Mechanistically, TMEM97 cooperates with PGRMC1 and LDLR to form a ternary complex that increases LDL internalization, placing σ₂R research in cholesterol trafficking and membrane-transport studies^[2]. In Alzheimer-related models, the TMEM97-PGRMC1-LDLR complex mediates cellular uptake of Aβ42 and its aggregates, supporting its use in amyloid-uptake experiments^[3]. In tumor models, σ₂R expression tracks proliferative status in solid tumors, making it useful for proliferation-focused oncology research^[4]. Compared with σ₁R, σ₂R/TMEM97 requires subtype-selective ligand validation, because classical DTG binding can overlap with σ₁R assays^[5]. For experimental design, TMEM97 or PGRMC1 knockout did not change sigma-2 ligand-induced cytotoxic EC₅₀ values in HeLa cells, so cytotoxicity should not be assigned automatically to either protein^[5]. For imaging applications,^{[^18F]}ISO-1 PET uptake has been evaluated as a marker of breast-cancer proliferation, linking σ₂R ligands to translational tumor-imaging studies^[6]. Recent cellular studies further show that sigma-2 receptor ligand binding modulates the association between TSPO and TMEM97, expanding mechanistic assays beyond PGRMC1-centered models^[7].