Biological And Biochemical Characterization Of Sigma Rec

这个项目描绘了sigma-1受体的生物化学和药理学特性。σ-1受体是位于内质网（ER）的单跨膜蛋白，可结合神经类固醇、苯并吗啡类和某些精神兴奋剂（如可卡因）。在这项研究中，我们发现sigma-1受体通过形成一种独特的脂质微区，特异性靶向内质网上的脂质储存位点（脂滴）。内源性表达的sigma-1受体和转染的C-末端EYFP标记的sigma-1受体（Sig-1 R-EYFP）的靶点是否独特？环状的NG 108 -15细胞中与内质网网状网络相关的结构。的？环状的结构含有中性脂质，并通过油酸酯处理扩大，表明它们是内质网相关脂滴（ER-LD）。σ-1受体与小窝蛋白-2共定位，小窝蛋白-2是ER-LD上脂筏中的胆固醇结合蛋白，但不与ADRP共定位，ADRP是细胞溶质脂滴（c-LD）特异性蛋白。当sigma-1受体N端的双精氨酸ER滞留信号被截短时，sigma-1受体不再存在于ER-LD上，而是主要靶向含有ADRP的c-LD。ER-LD上的Sigma-1受体形成耐洗涤剂的筏状脂质微区，其浮力不同于质膜脂筏。（+）喷他佐辛导致sigma-1受体从微区消失。N-末端EYFP标记的Sigma-1受体（EYFP-Sig-1 R）未能靶向ER-LD。EYFP-Sig-1 R转染的细胞显示中性脂质在整个内质网网络中不受限制地分布，质膜中的c-LD和胆固醇减少，以及内质网的球状聚集。因此，σ-1受体是独特的内质网蛋白，其调节内质网上脂质的区室化及其从内质网到质膜和c-LD的输出。

This project delineates biochemical and pharmacological properties of sigma-1 receptors. Sigma-1 receptors are one-transmembrane proteins at the endoplasmic reticulum (ER) that bind neurosteroids, dextrobenzomorphans, and certain psychostimulants such as cocaine. In this study, we found that sigma-1 receptors specifically target lipid storage sites (lipid droplets) on the endoplasmic reticulum by forming a distinct class of lipid microdomains. Both endogenously expressing sigma-1 receptors and transfected C-terminally EYFP-tagged sigma-1 receptors (Sig-1R-EYFP) target unique ?ring-like? structures associated with endoplasmic reticulum reticular networks in NG108-15 cells. The ?ring-like? structures contain neutral lipids and are enlarged by the oleate treatment, indicating that they are endoplasmic reticulum-associated lipid droplets (ER-LD). Sigma-1 receptors colocalize with caveolin-2, a cholesterol-binding protein in lipid rafts on the ER-LD, but not with ADRP, a cytosolic lipid droplet (c-LD) specific protein. When the double-arginine ER retention signal on the N-terminus of sigma-1 receptors is truncated, sigma-1 receptors no longer exist on ER-LD, but predominantly target c-LD which contain ADRP. Sigma-1 receptors on ER-LD form detergent-resistant raft-like lipid microdomains, the buoyancy of which is different from those of plasma membrane lipid rafts. (+)Pentazocine causes sigma-1 receptors to disappear from the microdomains. N-terminally EYFP-tagged Sigma-1 receptors (EYFP-Sig-1R) failed to target ER-LD. EYFP-Sig-1R-transfected cells showed an unrestricted distribution of neutral lipids all over the endoplasmic reticulum network, decreases in c-LD and cholesterol in plasma membranes, and the bulbous aggregation of endoplasmic reticulum. Thus, sigma-1 receptors are unique endoplasmic reticulum proteins that regulate the compartmentalization of lipids on the endoplasmic reticulum and their export from the endoplasmic reticulum to plasma membrane and c-LD.