Functional Studies of HSPA5 Promoter Polymorphisms and Risk of Essential Tremor in Taiwan

Abstract

蛋白質不正常摺疊引起的內質網壓力(ER stress)及不正常蛋白質摺疊反應(unfolded protein response; UPR)的機能失常，和神經退化性疾病的致病機制相關。70kDa熱休克蛋白5(HSPA5)為一UPR伴隨蛋白，可反應內質網壓力、抑制細胞凋零。HSPA5基因的啟動子多型性-415G/A(rs391957)、-370 C/T(rs17840761)及-180 del/G (rs3216733)可能影響其表現量。利用啟動子報告基因試驗，我們檢測了這三個多型性所暗示的功能。在神經癌SK-N-SH細胞中，帶有-415A多型性啟動子的螢光酵素報告質體表現的轉錄活性顯著低於帶有-415G者。利用個案－正常對照研究，我們分析了HSPA5基因啟動子多型性與台灣原發性顫抖症的相關性。在正常人(n=341)及原發性顫抖症患者(n=130)間，所分析的各多型性點，其基因型、等位基因與單套型頻率皆無顯著差異。我們的實驗數據顯示，HSPA5 -415 G/A多型性雖然影響其功能，但和台灣原發性顫抖症的風險無關。

Endoplasmic reticulum (ER) stress induced by misfolded proteins and a malfunction of unfolded protein response (UPR) to ER stress have been implicated in neurodegenerative disease pathogenesis. Heat shock 70 kDa protein 5 (HSPA5) is one of the UPR chaperones reactive to ER stress to block the apoptotic process. Three polymorphisms in the HSPA5 promoter region, -415 G/A (rs391957), -370 C/T (rsI7840761) and -180 del/G (rs3216733), may affect the gene expression. Using a reporter assay, we examined the functional implication of these three promoter polymorphisms. Reporter construct containing the polymorphic -415 A allele cloned into a luciferase reporter plasmid drove significantly lower transcriptional activity of HSPA5 compared with the common -415 G allele in human neuroblastoma SK-N-SH cells. The association of these polymorphisms with Taiwanese essential tremor (ET) was investigated using a case-control study. The genotype, allele or haplotype frequency distribution examined was not significantly different between the controls (n = 341) and the ET patients (n = 130). Our data suggest that while functionally, the HSPA5 -415 G/A polymorphism is unlikely to affect susceptibility to ET in Taiwanese subjects.