G蛋白、G蛋白偶联受体及其与心肌细胞肥厚关系的研究进展

心肌细胞肥厚既是许多心血管疾病常见的细胞形态学改变，又是共有的病理生理过程。众多刺激因子可以通过膜受体偶联的G蛋白引起心肌细胞肥厚。本文主要综述G蛋白、G蛋白偶联受体的组成、结构与功能变化，及在心肌细胞肥厚发生中的作用。     

G蛋白偶联受体激酶的研究进展

G蛋白偶联受体激酶(GRKs)属丝氨酸／酪氨酸蛋白激酶家族,其亚型广泛存在于各种组织, 能特异地使活化的G蛋白偶联受体(GPCR)发生磷酸化及脱敏化,从而终止后者介导的信号转导通路．现就G蛋白偶联受体激酶的结构、种类及分布、生物学功能及与疾病关系的新进展进行总结与概括,并对其发展进行了展望．     

冠心病患者巨噬细胞胆固醇流出的变化

目的研究冠心病患者血液中单核细胞分化为巨噬细胞并荷脂后胆固醇流出的影响机制。方法分离冠心病患者(试验组)和正常人群(对照组)外周静脉血中单核细胞,并用佛波酯诱导为巨噬细胞,收集分离血清,检测各项血脂指标并备用。细胞用[3H]胆固醇处理24 h使其荷脂,然后分为四组:对照组+正常血清、对照组+高脂血清、试验组+正常血清及试验组+高脂血清。分别检测ABCA1、ABCG1表达及胆固醇流出率。结果与对照组比较,试验组单核/巨噬细胞胆固醇流出能力受损,油红O染色显示细胞内脂质蓄积增加,细胞内胆固醇流出减少,但ABCA1和ABCG1的表达改变不明显。与正常血清比较,试验组及对照组中高脂血清明显影响胆固醇流出能力,细胞内脂质蓄积增加,细胞内胆固醇流出减少,但不影响ABCA1和ABCG1的表达。结论冠心病患者巨噬细胞胆固醇流出能力受损,可能与动脉粥样硬化性血管疾病的发生相关。     

G蛋白偶联受体120在肥胖患者腹部皮下和大网膜脂肪组织中的表达及其影响因素

目的探讨游离脂肪酸功能受体G蛋白偶联受体120（GPRl20）在肥胖患者腹部皮下脂肪组织和大网膜脂肪组织中mRNA表达情况及其相关的影响因素。方法于2010年9月至2011年8月选取广州医学院第三附属医院施行慢性胆囊炎择期手术的非超重患者[对照组,体质指数（BMI）〈23kg／m。]39例和肥胖患者（肥胖组,BMI≥25kg／m2）40例,测量体重、腰臀围、血糖、血脂等指标,用逆转录．聚合酶链反应法（RT．PCR）检测腹部大网膜与皮下脂肪组织GPRl20mRNA的表达水平。采用t检验、Pearson相关分析、偏相关分析和多元逐步回归进行统计学分析。结果（1）大网膜组织中的GPRl20mRNA表达在肥胖组（0．876±0．076）和对照组（0．621±0．052）均高于两组皮下脂肪组织中的水平（0．479±0．028、0．421±0．035）,差异有统计学意义（t值分别为-2．546、-2．211,均P〈0．05）。肥胖组大网膜的GPRl20mRNA表达量（0．876±0．076）高于对照组（0．621±0．052）,差异有统计学意义（t=-2．348,P〈0．05）,皮下脂肪GPRl20mRNA表达量在肥胖组（0．4794-0．028）与对照组（0．4214-0．035）之间差异无统计学意义（t=-0．584,P〉0．05）。（2）以大网膜脂肪组织GPRl20mRNA表达量为应变量,仅稳态模型胰岛素抵抗指数和腰臀比进入分析模型,所得模型R。=0．3730,标准偏回归系数分别为0．227和0．321。皮下脂肪GPRl20mRNA表达量与年龄、血酯等其他因素均无相关性（均P〉0．05）。结论肥胖患者腹部大网膜脂肪组织GPRl20mRNA表达明显升高,腹型肥胖、胰岛素抵抗是大网膜脂肪组织GPRl20表达水平的主要影响因素。     

游离脂肪酸与G蛋白偶联受体40

最近研究发现孤儿G蛋白偶联受体40(GPR40)的配体是中、长链的游离脂肪酸(FFAs),其基因定位于人类染色体19q13.1,基因编码产物由300个氨基酸残基组成。它在胰腺和脑组织表达丰富,在肝脏、心、骨骼肌等也有表达。FFAs与GPR40的结合可以产生一系列生物学效应,包括促进胰岛素的分泌等。另外,一些药物及脂肪酸的衍生物也可以激活该受体。这些有望为探讨肥胖症和糖尿病的发病机理及治疗等研究提供新的突破点。     

G蛋白偶联受体40的研究进展

G蛋白偶联受体40（GPR40）是中、长链游离脂肪酸的内源性受体。它介导了游离脂肪酸对葡萄糖刺激的胰岛素分泌的双时相效应。对GPR40敲除小鼠的研究表明，GPR40缺陷对高脂饮食下的脂肪肝、胰岛素抵抗及糖耐量异常的发生具有保护作用，而β细胞过度表达GPR40则导致β细胞功能的损伤和糖尿病的发生。     

游离脂肪酸与G蛋白偶联受体40

最近研究发现孤儿G蛋白偶联受体40(GPR40)的配体是中、长链的游离脂肪酸(FFAs)，其基因定位于人类染色体19q13．1，基因编码产物由300个氨基酸残基组成。它在胰腺和脑组织表达丰富，在肝脏、心、骨骼肌等也有表达。FFAs与GPR40的结合可以产生一系列生物学效应，包括促进胰岛素的分泌等。另外，一些药物及脂肪酸的衍生物也可以激活该受体。这些有望为探讨肥胖症和糖尿病的发病机理及治疗等研究提供新的突破点。     

G蛋白偶联受体激酶4在高血压中的研究进展

正原发性高血压是心血管系统的常见疾病之一,目前,我国高血压患病率约20%,影响人群超过2亿[1-3],而且呈现继续增高的趋势。原发性高血压可以引起脑血管病,肾小动脉硬化,左心室肥厚,充血性心力衰竭,肾衰竭和猝死等,严重影响着人们的身体健康,因此明确高血压的发病机制显得尤为重要。原发性高血压的发病机制极其复杂,遗传因素、环境因素以及众多的神经体液因子共同作用调控着血压的变化。这些体液因子包括多巴胺、血管紧张素、利钠肽、抗利尿激素     

普罗布考干预后小鼠血清对巨噬细胞胆固醇流出的影响

目的 观察普罗布考处理后小鼠血清及不同浓度普罗布考体外干预对巨噬细胞胆固醇流出的影响,探讨普罗布考调节细胞胆固醇流出的可能机制.方法 16只健康雄性C57 BL/6J小鼠随机分为两组,分别给予普通饮食或添加普罗布考饲料饲养4周后,收集血清,酶法测定血清脂质;以乙酰化低密度脂蛋白和3H-胆固醇标记巨噬细胞,并以不同浓度普罗布考干预细胞,然后以上述血清介导,测定细胞胆固醇流出;收集干预后的细胞,提取mRNA及膜蛋白,分别检测ATP结合盒转运子A1和G1、B族Ⅰ型清道夫受体的表达.结果 普罗布考干预4周后小鼠血清较对照组介导更多的胆固醇从巨噬细胞流出,普罗布考呈剂量依赖性地增加巨噬细胞ATP结合盒转运子G1基因和蛋白的表达,并加速血清诱导的胆固醇流出率,而对B族Ⅰ型清道夫受体、ATP结合盒转运子A1基因和蛋白表达无明显影响.结论 普罗布考干预后的小鼠血清显著促进巨噬细胞胆固醇流出,其机制可能是通过增加ATP结合盒转运子G1的表达,而与细胞膜B族Ⅰ型清道夫受体、ATP结合盒转运子A1的表达无关.     

A heterodimer-selective agonist shows in vivo relevance of G protein-coupled receptor dimers

There has been much speculation regarding the functional relevance of G protein-coupled receptor heterodimers, primarily because demonstrating their existence in vivo has proven to be a considerable challenge. Here we show that the opioid agonist ligand 6'-guanidinonaltrindole (6'-GNTI) has the unique property of selectively activating only opioid receptor heterodimers but not homomers. Importantly, 6'-GNTI is an analgesic, thereby demonstrating that opioid receptor heterodimers are indeed functionally relevant in vivo. However, 6'-GNTI induces analgesia only when it is administered in the spinal cord but not in the brain, suggesting that the organization of heterodimers is tissue-specific. This study demonstrates a proof of concept for tissue-selective drug targeting based on G protein-coupled receptor heterodimerization. Importantly, targeting opioid heterodimers could provide an approach toward the design of analgesic drugs with reduced side effects.     

A selective peroxisome proliferator-activated receptor delta agonist promotes reverse cholesterol transport

The peroxisome proliferator-activated receptors (PPARs) are dietary lipid sensors that regulate fatty acid and carbohydrate metabolism. The hypolipidemic effects of the fibrate drugs and the antidiabetic effects of the glitazone drugs in humans are due to activation of the alpha (NR1C1) and gamma (NR1C3) subtypes, respectively. By contrast, the therapeutic potential of the delta (NR1C2) subtype is unknown, due in part to the lack of selective ligands. We have used combinatorial chemistry and structure-based drug design to develop a potent and subtype-selective PPARdelta agonist, GW501516. In macrophages, fibroblasts, and intestinal cells, GW501516 increases expression of the reverse cholesterol transporter ATP-binding cassette A1 and induces apolipoprotein A1-specific cholesterol efflux. When dosed to insulin-resistant middle-aged obese rhesus monkeys, GW501516 causes a dramatic dose-dependent rise in serum high density lipoprotein cholesterol while lowering the levels of small-dense low density lipoprotein, fasting triglycerides, and fasting insulin. Our results suggest that PPARdelta agonists may be effective drugs to increase reverse cholesterol transport and decrease cardiovascular disease associated with the metabolic syndrome X.     

Absence of the G protein-coupled receptor G2A in mice promotes monocyte/endothelial interactions in aorta

The G protein-coupled receptor G2A is highly expressed on macrophages and lymphocytes and has been localized to atherosclerotic plaques. We examined the role of G2A in modulating monocyte/endothelial interactions in the vessel wall. We measured adhesion of WEHI 78/24 monocytes to aortas of C57BL/6 (B6) and G2A-deficient (G2A(-/-)) mice using an ex vivo adhesion assay. G2A(-/-) mice had 10-fold elevations in adhesion of monocytes to aortas. Injection of GFP-expressing wild-type macrophages into B6 and G2A(-/-) mice in vivo showed increased macrophage accumulation in the aortic wall of G2A(-/-) mice. We isolated aortic endothelial cells (ECs) from B6 and G2A(-/-) mice and found a 2-fold increase in intercellular adhesion molecule-1 and E-selectin surface expression on G2A(-/-) ECs using flow cytometry. Using ELISA, we found a 3-fold increase in interleukin-6 and monocyte chemoattractant protein-1 production by G2A(-/-) ECs compared with B6 ECs. We found a dramatic increase in nuclear localization of the p65 subunit of nuclear factor kappaB in G2A(-/-) ECs. Transfection of G2A into G2A(-/-) ECs to restore normal expression levels reduced p65 nuclear localization to 35%. Restoration of G2A expression in G2A(-/-) ECs significantly reduced intercellular adhesion molecule-1 and endothelial selectin surface expression and reduced monocyte chemoattractant protein-1 and interleukin-6 production. Restoring G2A to G2A(-/-) ECs reduced monocyte adhesion by 80% compared with G2A(-/-) ECs in a flow chamber assay. Absence of G2A in endothelium results in proinflammatory signaling and increased monocyte/endothelial interactions in the aortic wall. Thus, endothelial G2A expression may aid in prevention of vascular inflammation and atherosclerosis.     

Regulation of G protein-coupled receptor kinases

G protein-coupled receptor kinases (GRKs) specifically interact with the agonist-activated form of G protein-coupled receptors (GPCRs) to effect receptor phosphorylation and desensitization. Recent studies demonstrate that GRK function is a highly regulated process, and it is perhaps in this manner that a handful of GRKs (7 have been identified to date) are able to regulate the responsiveness of numerous GPCRs in a given cell type in a coordinated manner. The mechanisms by which GRK activity is regulated can be divided into 3 categories: 1) subcellular localization; 2) alterations in intrinsic kinase activity; and 3) alterations in GRK expression levels. This review will summarize our current understanding of each of these regulatory processes, and offer explanations as to how such mechanisms influence GPCR regulation under various physiologic conditions.