Ohta Y, Tanizawa Y, Inoue H, Hosaka T, Ueda K, Matsutani A, Repunte V P, Yamada M, Kurachi Y, Bryan J, Aguilar-Bryan L, Permutt M A, Oka Y
Third Department of Internal Medicine, Yamaguchi University, School of Medicine, Ube, Japan.
Diabetes. 1998 Mar;47(3):476-81. doi: 10.2337/diabetes.47.3.476.
The sulfonylurea receptor 1 (SUR1) is an essential regulatory subunit of the beta-cell ATP-sensitive K+ channel (K[ATP]). The possible role of SUR1 gene mutation(s) in the development of NIDDM remains controversial as both a positive association and negative linkage results have been reported. Therefore, we examined the SUR1 gene at the single nucleotide level with single strand conformation polymorphism analysis in 100 Japanese NIDDM patients. We identified a total of five amino acid substitutions and 17 silent mutations by examining all 39 exons of this gene. Two rare novel mutations, D811N in exon 20 and R835C in exon 21, were identified in the first nucleotide-binding fold (NBF), a functionally important region of SUR1, in one patient each, both heterozygotes. To analyze possible functional alterations, we reconstituted the mutant K(ATP) by coexpressing beta-cell inward rectifier (BIR) (Kir 6.2), a channel subunit of K(ATP), and mutant SUR1 in HEK293T and COS-7 cells. As demonstrated by the patch clamp technique and rubidium (Rb+) efflux studies, neither mutation alters the properties of channel activities. Two other rare missense mutations, R275Q in exon 6 and V560M in exon 12, were also identified. The R275Q substitution was not found in 67 control subjects, and V560M was present in three control subjects. Neither of these substitutions appeared to cosegregate with NIDDM in the probands' families. A previously reported S1370A substitution located in the second NBF was also common in the Japanese subjects (allelic frequency 0.37), and was found at an equal frequency in nondiabetic control subjects. In conclusion, SUR1 mutations impairing K(ATP) function do not appear to be major determinants of NIDDM susceptibility in Japanese.
磺脲类受体1（SUR1）是β细胞ATP敏感性钾通道（K[ATP]）的重要调节亚基。SUR1基因突变在非胰岛素依赖型糖尿病（NIDDM）发生发展中的可能作用仍存在争议，因为既有阳性关联结果报道，也有阴性连锁结果报道。因此，我们采用单链构象多态性分析在单核苷酸水平检测了100例日本NIDDM患者的SUR1基因。通过检测该基因的所有39个外显子，我们共鉴定出5个氨基酸替换和17个沉默突变。在一名杂合子患者中，分别在SUR1功能重要区域的第一个核苷酸结合结构域（NBF）中发现了两个罕见的新突变，即第20外显子中的D811N和第21外显子中的R835C。为了分析可能的功能改变，我们在HEK293T和COS-7细胞中共表达β细胞内向整流器（BIR）（Kir 6.2）（K[ATP]的通道亚基）和突变型SUR1，重构了突变型K(ATP)。膜片钳技术和铷（Rb+）外流研究表明，这两种突变均未改变通道活性特性。还鉴定出另外两个罕见的错义突变，即第6外显子中的R275Q和第12外显子中的V560M。在67名对照受试者中未发现R275Q替换，而在3名对照受试者中存在V560M。在先证者家族中，这两种替换似乎均未与NIDDM共分离。先前报道的位于第二个NBF中的S1370A替换在日本受试者中也很常见（等位基因频率为0.37），在非糖尿病对照受试者中的频率相同。总之，在日本人中，损害K(ATP)功能的SUR1突变似乎不是NIDDM易感性的主要决定因素。
