Intracellular orphan receptor that binds numerous drugs and which is highly expressed in various proliferating cancer cells (PubMed:28559337). Corresponds to the sigma-2 receptor, which is thought to play important role in regulating cell survival, morphology and differentiation (PubMed:23922215, PubMed:25620095). Under investigation for its potential diagnostic and therapeutic uses (PubMed:23922215, PubMed:25620095). May play a role as a regulator of cellular cholesterol homeostasis (PubMed:19583955). May function as sterol isomerase (PubMed:25566323). May alter the activity of some cytochrome P450 proteins (PubMed:22292588). Interacts with NPC1. Localized at cell membrane and in lysosomes in sterol-depleted cells when expression of endogenous TMEM97 is stimulated. Widely expressed in normal tissues. Expressed in pancreatic, renal, breast, colon, ovarian surface epithelial (OSE) cells. Highly expressed in various proliferating cancer cells (PubMed:23922215). Up-regulated in ovarian surface epithelial (OSE) cells with progesterone. Sigma receptors are classified into two subtypes (Sigma-1 and Sigma-2) based on their different pharmacological profile. Sigma-2 receptors are identified by radioligand-binding studies as a binding site with high affinity for di-o-tolylguanidine (DTG) and haloperidol. Potentially useful for cancer diagnostics or as target for anticancer therapeutics or adjuvant anticancer treatment agents (PubMed:23922215). Some exogenous ligands display a neuroprotective effect (PubMed:25620095). Belongs to the TMEM97/sigma-2 receptor family. The molecular identity of the sigma-2 receptor has been unclear for a long time. It is now identified as TMEM97 (PubMed:28559337). Previously identified as PGRMC1 (AC O00264) (PubMed:22292588, PubMed:28007569).