Bjørbaek C, Vik T A, Echwald S M, Yang P Y, Vestergaard H, Wang J P, Webb G C, Richmond K, Hansen T, Erikson R L
Steno Diabetes Center, Copenhagen, Denmark.
Diabetes. 1995 Jan;44(1):90-7. doi: 10.2337/diab.44.1.90.
Complementary DNA encoding three catalytic subunits of protein phosphatase 1 (PP1 alpha, PP1 beta, and PP1 gamma) and the insulin-stimulated protein kinase 1 (ISPK-1) was analyzed for variations in the coding regions related to insulin-resistant glycogen synthesis in skeletal muscle of 30 patients with non-insulin-dependent diabetes mellitus (NIDDM). The human ISPK-1 cDNA was cloned from T-cell leukemia and placental cDNA libraries and mapped to the short arm of the human X chromosome. Single-strand conformation polymorphism (SSCP) analysis identified a total of six variations in the coding regions of the PP1 genes: two in PP1 alpha at codons 90 and 255; one in PP1 beta at codon 67; and three in PP1 gamma at codons 11,269, and 273, respectively. All were, however, silent single nucleotide substitutions. SSCP analysis of the ISPK-1 gene identified one silent polymorphism at codon 266 and one amino acid variant at codon 38 (Ile-->Ser). This variant was primarily found in one male NIDDM patient. This subject, however, did not exhibit an impairment of muscle insulin-stimulated glycogen synthase activation. No significant differences were found in mRNA levels in muscle of the four genes between 15 NIDDM patients and 14 healthy subjects. Our findings suggest that 1) genetic abnormalities in the coding regions of PP1 alpha, PP1 beta, PP1 gamma, and ISPK-1 are unlikely to be frequently occurring causes of the reduced insulin-stimulated activation of the glycogen synthesis in muscle from the analyzed group of NIDDM patients; 2) the mRNA levels of PP1 alpha, PP1 beta, PP1 gamma, and ISPK-1 are normal in muscle from the NIDDM patients; and 3) putative inherited defects in insulin-stimulated activation of muscle glycogen synthesis in patients with insulin-resistant NIDDM may be located further upstream of ISPK-1 in the insulin action cascade.
对编码蛋白磷酸酶1的三个催化亚基（PP1α、PP1β和PP1γ）以及胰岛素刺激蛋白激酶1（ISPK-1）的互补DNA进行分析，以研究30例非胰岛素依赖型糖尿病（NIDDM）患者骨骼肌中与胰岛素抵抗性糖原合成相关的编码区变异。人ISPK-1 cDNA从T细胞白血病和胎盘cDNA文库中克隆出来，并定位到人类X染色体短臂。单链构象多态性（SSCP）分析在PP1基因的编码区共鉴定出六个变异：PP1α中密码子90和255处有两个；PP1β中密码子67处有一个；PP1γ中密码子11、269和273处分别有三个。然而，所有这些都是沉默的单核苷酸替换。ISPK-1基因的SSCP分析在密码子266处鉴定出一个沉默多态性，在密码子38处鉴定出一个氨基酸变体（Ile→Ser）。这种变体主要在一名男性NIDDM患者中发现。然而，该患者并未表现出肌肉胰岛素刺激的糖原合酶激活受损。15例NIDDM患者和14名健康受试者的四个基因在肌肉中的mRNA水平未发现显著差异。我们的研究结果表明：1）PP1α、PP1β、PP1γ和ISPK-1编码区的基因异常不太可能是所分析的NIDDM患者组肌肉中胰岛素刺激的糖原合成激活降低的常见原因；2）NIDDM患者肌肉中PP1α、PP1β、PP1γ和ISPK-1的mRNA水平正常；3）胰岛素抵抗性NIDDM患者中胰岛素刺激的肌肉糖原合成激活的推定遗传缺陷可能位于胰岛素作用级联中ISPK-1的更上游。
