σ-1 Receptor at the Mitochondrial-Associated Endoplasmic Reticulum Membrane Is Responsible for Mitochondrial Metabolic Regulation
作者:Karla-Sue C. Marriott、Manoj Prasad、Veena Thapliyal、Himangshu S. Bose
DOI:10.1124/jpet.112.198168
日期:2012.12
The mitochondria-associated endoplasmic reticulum (ER) membrane (MAM) is a small section of the outer mitochondrial membrane tethered to the ER by lipid and protein filaments. One such MAM protein is the σ-1 receptor, which contributes to multiple signaling pathways. We found that short interfering RNA-mediated knockdown of σ-1 reduced pregnenolone synthesis by 95% without affecting expression of the inner mitochondrial membrane resident enzyme, 3-β-hydroxysteroid dehydrogenase 2. To explore the underlying mechanism of this effect, we generated a series of σ-receptor ligands: 5,6-dimethoxy-3-methyl- N -phenyl- N -(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamide (KSCM-1), 3-methyl- N -phenyl- N -(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamide (KSCM-5), and 6-methoxy-3-methyl- N -phenyl- N -(3-(piperidin-1-yl) propyl)benzofuran-2-carboxamide (KSCM-11) specifically bound to σ-1 in the nanomolar range, whereas KSCM-5 and KSCM-11 also bound to σ-2. Treatment of cells with the KSCM ligands led to decreased cell viability, with KSCM-5 having the most potent effect followed by KSCM-11. KSCM-1 increased σ-1 expression by 4-fold and progesterone synthesis, whereas the other compounds decreased progesterone synthesis. These differences probably are caused by ligand molecular structure. For example, KSCM-1 has two methoxy substituents at C-5 and C-6 of the benzofuran ring, whereas KSCM-11 has one at C-6. KSCM ligands or σ-1 knockdown did not alter the expression of ER resident enzymes that synthesize steroids. However, coimmunoprecipitation of the σ-1 receptor pulled down voltage-dependent anion channel 2 (VDAC2), whose expression was enhanced by KSCM-1. VDAC2 plays a key role in cholesterol transport into the mitochondria, suggesting that the σ-1 receptor at the MAM coordinates with steroidogenic acute regulatory protein for cholesterol trafficking into the mitochondria for metabolic regulation.
线粒体相关内质网(ER)膜(MAM)是线粒体外膜的一小部分,通过脂质和蛋白丝与ER相连。σ-1受体就是这样一种MAM蛋白,它有助于多种信号通路。我们发现,短干扰 RNA 介导的σ-1 基因敲除减少了 95% 的孕烯醇酮合成,而不影响线粒体内膜常驻酶 3-β- 羟基类固醇脱氢酶 2 的表达。为了探索这种效应的内在机制,我们生成了一系列σ受体配体:5,6-二甲氧基-3-甲基-N-苯基-N-(3-(哌啶-1-基)丙基)苯并呋喃-2-甲酰胺(KSCM-1)、3-甲基-N-苯基-N-(3-(哌啶-1-基)丙基)苯并呋喃-2-甲酰胺(KSCM-5)、和 6-甲氧基-3-甲基-N-苯基-N-(3-(哌啶-1-基)丙基)苯并呋喃-2-甲酰胺(KSCM-11)在纳摩尔范围内特异性地与σ-1 结合,而 KSCM-5 和 KSCM-11 也与σ-2 结合。用 KSCM 配体处理细胞会导致细胞活力下降,其中 KSCM-5 的效果最强,其次是 KSCM-11。KSCM-1 使 σ-1 的表达和孕酮的合成增加了 4 倍,而其他化合物则减少了孕酮的合成。这些差异可能是配体分子结构造成的。例如,KSCM-1 在苯并呋喃环的 C-5 和 C-6 上有两个甲氧基取代基,而 KSCM-11 在 C-6 上只有一个。KSCM配体或σ-1基因敲除不会改变合成类固醇的ER常驻酶的表达。然而,σ-1 受体的共免疫沉淀拉低了电压依赖性阴离子通道 2(VDAC2)的表达,而 KSCM-1 则增强了 VDAC2 的表达。VDAC2 在胆固醇转运到线粒体的过程中起着关键作用,这表明 MAM 上的σ-1 受体与类固醇生成急性调节蛋白协调,将胆固醇转运到线粒体以进行代谢调节。