Subramanian Lakshmi, Khan Abrar A, Allu Prasanna K R, Kiranmayi Malapaka, Sahu Bhavani S, Sharma Saurabh, Khullar Madhu, Mullasari Ajit S, Mahapatra Nitish R
From the Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600036.
Department of Experimental Medicine and Biotechnology, Postgraduate Institute of Medical Education and Research, Chandigarh 160012, India.
J Biol Chem. 2017 Aug 25;292(34):13970-13985. doi: 10.1074/jbc.M117.778134. Epub 2017 Jun 30.
The acidic glycoprotein chromogranin A (CHGA) is co-stored/co-secreted with catecholamines and crucial for secretory vesicle biogenesis in neuronal/neuroendocrine cells. CHGA is dysregulated in several cardiovascular diseases, but the underlying mechanisms are not well established. Here, we sought to identify common polymorphisms in the promoter and to explore the mechanistic basis of their plausible contribution to regulating CHGA protein levels in circulation. Resequencing of the promoter in an Indian population ( = 769) yielded nine single-nucleotide polymorphisms (SNPs): G-1106A, A-1018T, T-1014C, T-988G, G-513A, G-462A, T-415C, C-89A, and C-57T. Linkage disequilibrium (LD) analysis indicated strong LD among SNPs at the -1014, -988, -462, and -89 bp positions and between the -1018 and -57 bp positions. Haplotype analysis predicted five major promoter haplotypes that displayed differential promoter activities in neuronal cells; specifically, haplotype 2 (containing variant T alleles at -1018 and -57 bp) exhibited the highest promoter activity. Systematic computational and experimental analyses revealed that transcription factor c-Rel has a role in activating the promoter haplotype 2 under basal and pathophysiological conditions ( inflammation and hypoxia). Consistent with the higher promoter activity of haplotype 2, individuals carrying this haplotype had higher plasma CHGA levels, plasma glucose levels, diastolic blood pressure, and body mass index. In conclusion, these results suggest a functional role of the promoter haplotype 2 (occurring in a large proportion of the world population) in enhancing CHGA expression in haplotype 2 carriers who may be at higher risk for cardiovascular/metabolic disorders.
酸性糖蛋白嗜铬粒蛋白A（CHGA）与儿茶酚胺共同储存/共同分泌，对神经元/神经内分泌细胞中分泌囊泡的生物发生至关重要。CHGA在几种心血管疾病中表达失调，但其潜在机制尚未完全明确。在此，我们试图鉴定启动子中的常见多态性，并探讨它们可能影响循环中CHGA蛋白水平的潜在机制。对印度人群（n = 769）的启动子进行重测序，发现了9个单核苷酸多态性（SNP）：G-1106A、A-1018T、T-1014C、T-988G、G-513A、G-462A、T-415C、C-89A和C-57T。连锁不平衡（LD）分析表明，在-1014、-988、-462和-89 bp位置的SNP之间以及-1018和-57 bp位置之间存在强LD。单倍型分析预测了五种主要的启动子单倍型，它们在神经元细胞中表现出不同的启动子活性；具体而言，单倍型2（在-1018和-57 bp处含有变异T等位基因）表现出最高的启动子活性。系统的计算和实验分析表明，转录因子c-Rel在基础和病理生理条件（炎症和缺氧）下激活启动子单倍型2中发挥作用。与单倍型2较高的启动子活性一致，携带该单倍型的个体血浆CHGA水平、血糖水平、舒张压和体重指数较高。总之，这些结果表明启动子单倍型2（在世界上很大一部分人群中出现）在增强单倍型2携带者中CHGA表达方面具有功能作用，这些携带者可能患心血管/代谢疾病的风险更高。
