title: Detergent-resistant microdomains determine the localization of sigma-1 receptors to the endoplasmic reticulum-mitochondria junction.
abstract: Sigma-1 receptors (Sig-1Rs) that bind diverse synthetic and endogenous compounds have been implicated in the pathophysiology of several human diseases such as drug addiction, depression, neurodegenerative disorders, pain-related disorders, and cancer. Sig-1Rs were identified recently as novel ligand-operated molecular chaperones. Although Sig-1Rs are predominantly expressed at endoplasmic reticulum (ER) subdomains apposing mitochondria [i.e., the mitochondria-associated ER membrane (MAM)], they dynamically change the cellular distribution, thus regulating both MAM-specific and plasma membrane proteins. However, what determines the location of Sig-1R at the MAM and how the receptor translocation is initiated is unknown. Here we report that the detergent-resistant membranes (DRMs) play an important role in anchoring Sig-1Rs to the MAM. The MAM, which is highly capable of accumulating ceramides, is enriched with both cholesterol and simple sphingolipids, thus forming Triton X-114-resistant DRMs. Sig-1Rs associate with MAM-derived DRMs but not with those from microsomes. A lipid overlay assay found that solubilized Sig-1Rs preferentially associate with simple sphingolipids such as ceramides. Disrupting DRMs by lowering cholesterol or inhibiting de novo synthesis of ceramides at the ER largely decreases Sig-1R at DRMs and causes translocation of Sig-1R from the MAM to ER cisternae. These findings suggest that the MAM, bearing cholesterol and ceramide-enriched microdomains at the ER, may use the microdomains to anchor Sig-1Rs to the location; thus, it serves to stage Sig-1R at ER-mitochondria junctions.
authors.affiliation: Cellular Pathobiology Section, Cellular Neurobiology Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, MD 21224, USA. thayashi@mail.nih.gov
authors.forename: Teruo
authors.initials: T
authors.lastname: Hayashi
authors.forename: Michiko
authors.initials: M
authors.lastname: Fujimoto
mesh_terms: D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D002518:Ceramides / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D003902:Detergents / Q000494:pharmacology*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D037341:Fumonisins / Q000494:pharmacology; D006801:Humans; D021962:Membrane Microdomains / Q000502:physiology*; D008928:Mitochondria / Q000378:metabolism*; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000494:pharmacology*; D017480:Receptors, sigma / Q000737:chemistry / Q000378:metabolism*; D012995:Solubility; D013107:Sphingolipids / Q000378:metabolism; D000097605:Sigma-1 Receptor
chemical_list: D002118:Calcium; D002518:Ceramides; D003902:Detergents; D037341:Fumonisins; D017830:Octoxynol; D011092:Polyethylene Glycols; D017480:Receptors, sigma; D013107:Sphingolipids; D000097605:Sigma-1 Receptor; C056933:fumonisin B1; C010615:Nonidet P-40