KCNJ11 activating mutations in Italian patients with permanent neonatal diabetes

Permanent neonatal diabetes mellitus (PNDM) is a rare condition characterized by severe hyperglycemia constantly requiring insulin treatment from its onset. Complete deficiency of glucokinase (GCK) can cause PNDM; however, the genetic etiology is unknown in most PNDM patients. Recently, heterozygous activating mutations of KCNJ11, encoding Kir6.2, the pore forming subunit of the ATP-dependent potassium (K(ATP)) channel of the pancreatic beta-cell, were found in patients with PNDM. Closure of the K(ATP) channel exerts a pivotal role in insulin secretion by modifying the resting membrane potential that leads to insulin exocytosis. We screened the KCNJ11 gene in 12 Italian patients with PNDM (onset within 3 months from birth) and in six patients with non-autoimmune, insulin-requiring diabetes diagnosed during the first year of life. Five different heterozygous mutations were identified: c.149G>C (p.R50P), c.175G>A (p.V59M), c.509A>G (p.K170R), c.510G>C (p.K170N), and c.601C>T (p.R201C) in eight patients with diabetes diagnosed between day 3 and 182. Mutations at Arg50 and Lys170 residues are novel. Four patients also presented with motor and/or developmental delay as previously reported. We conclude that KCNJ11 mutations are a common cause of PNDM either in isolation or associated with developmental delay. Permanent diabetes of non autoimmune origin can present up to 6 months from birth in individuals with KCNJ11 and EIF2AK3 mutations. Therefore, we suggest that the acronym PNDM be replaced with the more comprehensive permanent diabetes mellitus of infancy (PDMI), linking it to the gene product (e.g., GCK-PDMI, KCNJ11-PDMI) to avoid confusion between patients with early-onset, autoimmune type 1 diabetes.     

雪莲的研究进展

雪莲是我国珍稀名贵的中药材，具有很高的药用价值，应用前景广阔。雪莲生长环境恶劣，自然资源十分有限。由于近年来野生雪莲乱采滥挖现象严重，加之人工栽培困难，雪莲已被列为国家三级濒危物种而受到保护。综述雪莲的有效成分、药理作用、开发利用现状及解决雪莲资源短缺的途径，并对雪莲今后研究发展的方向进行了展望，以期更加有效地保护和合理开发利用雪莲资源、满足医药市场需求、保护西部生态环境和促进西部经济发展。     

细胞内pH对胆碱能受体介导的Kir3.1/3.4电流的调节

目的　研究细胞内pH对胆碱能受体介导的Kir3 1/3 4电流的调节作用。方法　应用AzideNa、KHCO3 和通过灌流直接降低细胞内 pH ,用双电极电压钳和膜片钳方法观察在蛙卵细胞中表达的Kir3 1/ 3 4钾离子通道电流的变化和M受体激活对Kir3 1/ 3 4电流调节的变化。结果　细胞内 pH降低能抑制Kir3 1/ 3 4的电流 ;Kir3 1/ 3 4对细胞内pH的敏感性介于另外两种Kir通道Kir2 1和Kir2 3之间 ,即这三种通道对细胞内 pH的敏感性依次为Kir2 3>Kir3 1/ 3 4 >Kir2 1;细胞内pH降低能够减弱M1受体激活对Kir3 1/ 3 4的抑制作用 ,加强M2 受体激活Kir3 1/ 3 4电流后的去敏作用。结论　在维持细胞静息电位方面起重要作用的Kir3 1/ 3 4通道在细胞内pH降低的情况下基础电流和M受体激活调节电流均发生了变化 ,这些变化在缺血缺氧引起的细胞 (如心肌细胞 )兴奋性改变中可能有重要的生理学意义     

ATP敏感性钾通道SUR2B/Kir6.1亚型选择性开放剂纳他卡林的心血管药理学作用特征

目的研究SUR2B/Kir6.1亚型KATP通道开放剂纳他卡林的心血管药理学作用。方法(1)血流动力学测定:戊巴比妥钠腹腔注射麻醉大鼠,从颈总动脉插管至左心室,连接八导生理记录仪记录心功能的变化。(2)制备大鼠离体工作心脏,观察纳他卡林对其心功能的影响。(3)制备大鼠尾动脉血管条,用去甲肾上腺素预收缩后,观察累积给予纳他卡林对血管张力的影响。结果纳他卡林10-8～10-4mol.L-1对大鼠离体工作心脏功能无影响;对大鼠尾动脉血管条具有内皮细胞依赖性舒张作用。麻醉大鼠,纳他卡林0.5、2、8mg.kg-1静脉注射可剂量依赖性降低血压,纳他卡林8mg.kg-1抑制心脏的收缩和舒张功能,其效应可被格列苯脲和L-NAME拮抗。结论纳他卡林对心脏无直接作用,可通过舒张血管降低血压;纳他卡林的心血管药理学作用与其选择性开放KATP通道、促进内皮细胞释放NO有关。     

SUMOylation of Kir7.1 participates in neuropathic pain through regulating its membrane expression in spinal cord neurons

AimsPotassium (K⁺) channels have been demonstrated to play a prominent involvement in nociceptive processing. Kir7.1, the newest members of the Kir channel family, has not been extensively studied in the CNS, and its function remains largely unknown. The present study investigated the role of spinal Kir7.1 in the development of pathological pain.Methods and ResultsNeuropathic pain was induced by spared nerve injury (SNI). The mechanical sensitivity was assessed by von Frey test. Immunofluorescence staining assay revealed that Kir7.1 was predominantly expressed in spinal neurons but not astrocytes or microglia in normal rats. Western blot results showed that SNI markedly decreased the total and membrane expression of Kir7.1 in the spinal dorsal horn accompanied by mechanical hypersensitivity. Blocking Kir7.1 with the specific antagonist ML418 or knockdown kir7.1 by siRNA led to mechanical allodynia. Co‐IP results showed that the spinal kir7.1 channels were decorated by SUMO‐1 but not SUMO‐2/3, and Kir7.1 SUMOylation was upregulated following SNI. Moreover, inhibited SUMOylation by GA (E1 inhibitor) or 2‐D08 (UBC9 inhibitor) can increase the spinal surface Kir7.1 expression.ConclusionSUMOylation of the Kir7.1 in the spinal cord might contribute to the development of SNI‐induced mechanical allodynia by decreasing the Kir7.1 surface expression in rats.     

Kir 6.2激活突变与新生儿糖尿病

新生儿糖尿病是一类少见的内分泌代谢疾病.晚近发现,不少患儿携带Kir 6.2激活突变,突变的Kir 6.2通过影响ATP敏感性钾通道的正常关闭及胰岛素的释放而致病.此类突变患者大多对磺脲类药物较敏感,口服磺脲类药物有望成为主要的治疗手段.     

内向矫正性钾通道Kir4.1和Kir7.1在大鼠睫状体的分布

目的:在蛋白水平探讨Kir4.1和Kir7.1在大鼠睫状体的分布情况。方法:用间接免疫荧光组织化学和免疫荧光双标记在冰冻切片上检测Kir4.1和Kir7.1在大鼠睫状体的分布和定位。结果:Kir4.1蛋白分布于睫状体的色素上皮细胞和无色素上皮细胞的胞质和胞膜,内层的无色素上皮细胞免疫活性较强,免疫双标显示Kir4.1蛋白与谷氨酰胺合成酶蛋白重叠分布,Kir4.1蛋白免疫活性在睫状体的扁平部和睫状突上无明显差异。Kir7.1蛋白分布于睫状体的无色素上皮细胞和睫状肌,与特异性标记睫状上皮的Ezrin蛋白双标显示Kir7.1分布在无色素上皮的基底面,其免疫活性在睫状突强表达,在睫状体扁平部弱表达。结论:Kir4.1和Kir7.1均分布于大鼠睫状体的无色素上皮的基底面,可能与房水的生成有重要关系。睫状肌的Kir7.1分布,与调节睫状肌的舒缩、参与房水的排出密切相关。     

天山雪莲二倍体与四倍体总黄酮含量的测定与比较

目的测定与比较天山雪莲二倍体与四倍体组培苗总黄酮含量。为四倍体天山雪莲进一步开发利用奠定基础。方法用紫外分光光度法测定天山雪莲二倍体与四倍体总黄酮的含量。结果天山雪莲组培苗中,四倍体总黄酮含量大于二倍体总黄酮含量,且相对于二倍体总黄酮含量增加23％。结论四倍体天山雪莲在总黄酮含量上增高,具有开发利用价值。     

Focus on Kir6.2: a key component of the ATP-sensitive potassium channel

ATP-sensitive potassium (K(ATP)) channels are found in a wide variety of cell types where they couple cell metabolism to electrical activity. In glucose-sensing tissues, these channels respond to fluctuating changes in blood glucose concentration, but in other tissues they are activated only under ischemic conditions or in response to hormonal stimulation. Although K(ATP) channels in different tissues have different regulatory subunits, in almost all cases (except vascular smooth muscle) the pore-forming subunit is the inwardly rectifying K(+) channel Kir6.2. This article reviews recent studies of Kir6.2, focussing on the relation between channel structure and function, and on naturally occurring mutations in Kir6.2 that lead to human disease. New insights into the location of the ATP-binding site, the permeation pathway for K(+), and the gating of the pore provided by homology modelling are discussed in relation to functional studies. Gain-of-function mutations in Kir6.2 cause permanent neonatal diabetes mellitus (PNDM) by reducing the ATP sensitivity of the K(ATP) channel and increasing the K(ATP) current, which is predicted to inhibit beta-cell electrical activity and insulin secretion. Mutations at specific residues, that cause a greater decrease in ATP sensitivity, are associated with additional neurological symptoms. The molecular mechanism underlying the differences in ATP sensitivity produced by these two classes of mutations is discussed. We speculate on how some mutations lead to neurological disease and why no obvious cardiac symptoms are observed. We also consider the implications of these studies for type-2 diabetes.