Na+,K+-ATP酶与脑缺血

Na+,K+-ATP酶的基本功能是维持真核细胞膜内外Na+ - K+电化学梯度平衡,后者为维持细胞渗透压、调节细胞体积和维持可兴奋细胞膜静息电位所必需.Na+,K+ -ATP酶活性的维持在神经元神经递质的摄取和Ca2+外流中起着重要作用.脑缺血后,Na+,K+ -ATP酶活性降低及功能异常参与缺血性脑损伤过程.缺血预处理通过维持缺血后Na+,K+ -ATP酶活性而诱导缺血耐受.强心甾类固醇和胞二磷胆碱可通过提高Na+,K+ -ATP酶活性对脑缺血发挥神经保护效应.     

Na+,K+-ATP酶与脑缺血

Na+,K+-ATP酶的基本功能是维持真核细胞膜内外Na+ - K+电化学梯度平衡,后者为维持细胞渗透压、调节细胞体积和维持可兴奋细胞膜静息电位所必需.Na+,K+ -ATP酶活性的维持在神经元神经递质的摄取和Ca2+外流中起着重要作用.脑缺血后,Na+,K+ -ATP酶活性降低及功能异常参与缺血性脑损伤过程.缺血预处理通过维持缺血后Na+,K+ -ATP酶活性而诱导缺血耐受.强心甾类固醇和胞二磷胆碱可通过提高Na+,K+ -ATP酶活性对脑缺血发挥神经保护效应.     

Na+,K+-ATP酶与脑缺血

Na+,K+-ATP酶的基本功能是维持真核细胞膜内外Na+ - K+电化学梯度平衡,后者为维持细胞渗透压、调节细胞体积和维持可兴奋细胞膜静息电位所必需.Na+,K+ -ATP酶活性的维持在神经元神经递质的摄取和Ca2+外流中起着重要作用.脑缺血后,Na+,K+ -ATP酶活性降低及功能异常参与缺血性脑损伤过程.缺血预处理通过维持缺血后Na+,K+ -ATP酶活性而诱导缺血耐受.强心甾类固醇和胞二磷胆碱可通过提高Na+,K+ -ATP酶活性对脑缺血发挥神经保护效应.     

P/Q型钙通道α1亚基基因CACNA1A突变与偏头痛

偏头痛是一种常见的反复发作性疾病,有明显家族聚集性,发病机制未明。对家族性偏瘫型偏头痛(FHM)家系CACNA1A基因的鉴定,掀起了偏头痛分子遗传学研究的热潮。该基因定位于19p13,为脑特异性P/Q型钙通道α1A亚单位基因CACNA1A。业已鉴定出该基因的15种突变型。突变型与表现型之间存在一定的关系。但是,CACNA1A基因与普通型偏头痛是否相关的研究却得出了不同的结论。     

维吾尔族及汉族帕金森病患者ATP13A2基因Ala1144Thr突变比较

目的探讨ATP13A2基因Ala1144Thr位点突变在新疆维吾尔族(简称维族)、汉族散发性帕金森病(SPD)患者中是否存在差异性。方法 SPD患者(病例组)420例和健康成人(正常对照组)400例,采用聚合酶链反应(PCR)结合DNA直接测序法进行ATP13A2基因亚型Ala1144Thr突变分析;比较2个民族SPD患者Ala1144Thr位点基因多态性。结果新疆维汉SPD患者Ala1144Thr突变率为1/420(0.24%);ATP13A2基因Ala1144Thr多态性在PD组和正常对照组,男性PD组与女性PD组,维族PD组与汉族PD组,维族早发性PD(EOPD)组与汉族EOPD组,男性EOPD组与女性EOPD亚组,EOPD亚组与迟发性PD(LOPD)亚组,男性LOPD亚组与女性LOPD亚组,维族LOPD亚组与汉族LOPD亚组其基因型及等位基因型频率比较差异均无统计学意义(P0.05)。结论新疆族、汉族ATP13A2基因Ala1144Thr位点突变率极低,新疆族、汉族ATP13A2基因Ala1144Thr位点等位基因型与等位基因型频率与民族、发病年龄及性别均无明显相关性。     

ATP结合盒转运子A1基因R219K多态性与冠心病的关系

目的:检测冠心病患者及健康对照者ATP结合盒转运子A1(ABCA1)R219K基因多态性,探讨其与中国人冠心病以及血脂水平的关系。方法:选择234例冠心病患者(冠心病组)和198例正常对照者(对照组)为研究对象,用聚合酶链式反应-限制性片段长度多态性方法研究R219K基因多态性与冠心病和血脂水平的关系。结果:与对照组比较,冠心病组RR基因型频率(46·2%)明显高于对照组(33·8%)(P<0·05),而KK型频率(8·9%)显著低于对照组(15·2%)(P<0·05);与RR型患者相比,KK基因型患者血浆高密度脂蛋白(HDL)水平较高。基因型与血脂水平Logistic回归分析结果表明,三酰甘油、HDL、载脂蛋白A1与基因型相关。结论:ABCA1基因R219K变异可能具有动脉硬化保护作用。     

Na/K ATP酶活性及其ATP1A1基因多态性与2型糖尿病周围神经病变的相关性

目的研究大连地区汉族人Na／KATP酶活性及ATP1A1基因多态性与2型糖尿病（T2DM）周围神经病变（DPN）的关系。方法用聚合酶链反应-限制性片段长度多态性方法对大连地区的106例T2DM患者和45例正常对照者（NC）的ATP1A1基因进行扩增，对其基因多态性进行研究，并用比色法测定其红细胞的Na／KATP酶活性。结果与NC组相比，T2DM组红细胞Na／KATP酶活性降低，在伴有DPN组，Na／KATP酶活性的降低更为明显。在T2DM患者中，有DPN组与无DPN组相比，基因型分布差异有统计学意义（P〈0．05）。T2DM患者携带有限制性等位基因A与非携带者Na／KATP酶活性的差异有统计学意义（P〈0．05）。结论Na／KATP酶活性的降低在DPN的发病中起重要作用，Na／KATP酶的基因ATP1A1多态性与T2DM患者发生DPN相关。T2DM携带有限制性等位基因A的患者DPN的发生率低于非携带者。     

P／Q型钙通道α1亚基基因CACNA1A突变与偏头痛

偏头痛是一种常见的反复发作性疾病，有明显家族聚集性，发病机制未明。对家族性偏瘫型偏头痛（FHM）家系CACNA1A基因的鉴定，掀起了偏头痛分子遗传学研究的热潮。该基因定位于19p13，为脑特异性P／Q型钙通道α1A亚单位基因CACNA1A。业已鉴定出该基因的15种突变型。突变型与表现型之间存在一定的关系。但是，CACNA1A基因与普通型偏头痛是否相关的研究却得出了不同的结论。     

COL3 A1、COL1 A2基因与颅内动脉瘤

颅内动脉瘤的形成、发展和破裂是遗传和环境因素相互作用的结果,对于绝大部分颅内动脉瘤患者而言,其遗传方式可能是非经典的孟德尔遗传。一些研究表明,编码动脉壁主要细胞外基质蛋白的COL3A1和COL1A2基因与颅内动脉瘤存在密切联系。     

ATP结合盒转运蛋白A1与动脉粥样硬化

对Tangier病病因的研究,发现ATP结合盒转运蛋白A1(ATP binding cassette transport protein A1,ABCA1)在胆固醇逆向转运(reverse cholesterol transport,RCT)中起重要作用。ABCA1主要通过核受体PPARs途径发挥作用。ABCA1基因变异影响其功能。     

Alternating hemiplegia of childhood: a distinct clinical entity and ATP1A3-related disorders: A narrative review

Alternating Hemiplegia of Childhood (AHC) is a rare disorder with onset in the first 18 months of life characterized by stereotyped paroxysmal manifestations of tonic and dystonic attacks, nystagmus with other oculomotor abnormalities, respiratory and autonomic dysfunctions. AHC is often associated with epileptic seizures and developmental delay. Hemiplegic paroxysm is the most remarkable symptom, although AHC includes a large series of clinical manifestations that interfere with the disease course. No cure is available and the treatment involves many specialists and therapies. Flunarizine is the most commonly used drug for reducing the frequency and intensity of paroxysmal events. Mutations in ATP1A2, particularly in ATP1A3, are the main genes responsible for AHC. Some disorders caused by ATP1A3 variants have been defined as ATP1A3-related disorders, including rapid-onset dystonia-parkinsonism, cerebellar ataxia, pes cavus, optic atrophy, sensorineural hearing loss, early infant epileptic encephalopathy, child rapid-onset ataxia, and relapsing encephalopathy with cerebellar ataxia. Recently, the term ATP1A3 syndrome has been identified as a fever-induced paroxysmal weakness and encephalopathy, slowly progressive cerebellar ataxia, childhood–onset schizophrenia/autistic spectrum disorder, paroxysmal dyskinesia, cerebral palsy/spastic paraparesis, dystonia, dysmorphism, encephalopathy, MRI abnormalities without hemiplegia, and congenital hydrocephalus. Herewith, we discussed about historical annotations of AHC, symptoms, signs and associated morbidities, diagnosis and differential diagnosis, treatment, prognosis, and genetics. We also reported on the ATP1A3-related disorders and ATP1A3 syndrome, as 2 recently established and expanded genetic clinical entities.     

K+-induced dilation of hamster cremasteric arterioles involves both the Na+/K+-ATPase and inward-rectifier K+ channels

OBJECTIVE: The mechanism by which elevated extracellular potassium ion concentration ([K+]o) causes dilation of skeletal muscle arterioles was evaluated. METHODS: Arterioles (n = 111) were hand-dissected from hamster cremaster muscles, cannulated with glass micropipettes and pressurized to 80 cm H2O for in vitro study. The vessels were superfused with physiological salt solution containing 5 mM KCl, which could be rapidly switched to test solutions containing elevated [K+]o and/or inhibitors. The authors measured arteriolar diameter with a computer-based diameter tracking system, vascular smooth muscle cell membrane potential with sharp micropipettes filled with 200 mM KCl, and changes in intracellular Ca2+ concentration ([Ca2+]i) with Fura 2. Membrane currents and potentials also were measured in enzymatically isolated arteriolar muscle cells using patch clamp techniques. The role played by inward rectifier K+ (KIR) channels was tested using Ba2+ as an inhibitor. Ouabain and substitution of extracellular Na+ with Li+ were used to examine the function of the Na+/K+ ATPase. RESULTS: Elevation of [K+]o from 5 mM up to 20 mM caused transient dilation of isolated arterioles (27 +/- 1 microm peak dilation when [K+]o was elevated from 5 to 20 mM, n = 105, p <.05). This dilation was preceded by transient membrane hyperpolarization (10 +/-1 mV, n = 23, p <.05) and by a fall in [Ca2+]i as indexed by a decrease in the Fura 2 fluorescence ratio of 22 +/- 5% (n = 4, p <.05). Ba(2+) (50 or 100 microM) attenuated the peak dilation (40 +/- 8% inhibition, n = 22) and hyperpolarization (31 +/- 12% inhibition, n = 7, p <.05) and decreased the duration of responses by 37 +/-11% (n = 20, p < 0.05). Both ouabain (1 mM or 100 microM) and replacement of Na+ with Li+ essentially abolished both the hyperpolarization and vasodilation. CONCLUSIONS: Elevated [K+]o causes transient vasodilation of skeletal muscle arterioles that appears to be an intrinsic property of the arterioles. The results suggest that K+-induced dilation involves activation of both the Na+/K+ ATPase and KIR channels, leading to membrane hyperpolarization, a fall in [Ca2+]i, and culminating in vasodilation. The Na+/K+ ATPase appears to play the major role and is largely responsible for the transient nature of the response to elevated [K+]o, whereas KIR channels primarily affect the duration and kinetics of the response.     

Identification of Novel ROR2 Gene Mutations in Indian Children with Robinow Syndrome

Ob­jec­ti­ve: Robinow syndrome (RS) is an extremely rare genetic disorder characterized by short-limbed dwarfism, defects in vertebral segmentation and abnormalities in the head, face and external genitalia. Mutations in the ROR2 gene cause autosomal recessive RS (RRS) whereas mutations in WNT5A are responsible for the autosomal dominant (AD) form of RS. In AD Robinow patients, oral manifestations are more prominent, while hemivertebrae and scoliosis rarely occur and facial abnormalities tend to be milder.Methods: Three unrelated patients from different parts of India were studied. These patients were diagnosed as RRS due to presence of characteristic fetal facies, mesomelia, short stature, micropenis, hemivertebrae and rib abnormalities. One of the patients had fetal facies and micropenis but unusually mild skeletal features. This patient’s mother had mild affection in the form of short stature and prominent eyes. Testosterone response to human chorionic gonadotropin was investigated in two patients and were normal. The exons and exon-intron boundaries of the ROR2 gene were sequenced for all probands. Bioinformatics analysis was done for putative variants using SIFT, PolyPhen2 and Mutation Taster.Results: Patients 1, 2 and 3 were homozygous for c.G545A or p.C182Y in exon 5, c.227G>A or p.G76D in exon 3 and c.668G>A or p.C223Y in exon 6 respectively. Prenatal diagnosis could be performed in an ongoing pregnancy in one family and the fetus was confirmed to be unaffected. Conclusion: ROR2 mutations were documented for the first time in the Indian population. Knowledge of the molecular basis of the disorder served to provide accurate counseling and prenatal diagnosis to the families.     

Altered Na+/Ca2+-exchanger activity due to downregulation of Na+/K+-ATPase alpha2-isoform in heart failure

AIMS: The Na+/K+-ATPase (NKA) alpha2-isoform is preferentially located in the t-tubules of cardiomyocytes and is functionally coupled to the Na+/Ca(+-exchanger (NCX) and Ca2+ regulation through intracellular Na+ concentration ([Na+]i). We hypothesized that downregulation of the NKA alpha2-isoform during congestive heart failure (CHF) disturbs the link between Na+ and Ca2+, and thus the control of cardiomyocyte contraction. METHODS AND RESULTS: NKA isoform and t-tubule distributions were studied using immunocytochemistry, confocal and electron microscopy in a post-infarction rat model of CHF. Sham-operated rats served as controls. NKA and NCX currents (I NKA and I NCX) were measured and alpha2-isoform current (I NKA,alpha2) was separated from total I NKA using 0.3 microM ouabain. Detubulation of cardiomyocytes was performed to assess the presence of alpha2-isoforms in the t-tubules. In CHF, the t-tubule network had a disorganized appearance in both isolated cardiomyocytes and fixed tissue. This was associated with altered expression patterns of NKA alpha1- and alpha2-isoforms. I NKA,alpha2 density was reduced by 78% in CHF, in agreement with decreased protein expression (74%). When I NKA,alpha2 was blocked in Sham cardiomyocytes, contractile parameters converged with those observed in CHF. In Sham, abrupt activation of I NKA led to a decrease in I NCX, presumably due to local depletion of [Na+]i in the vicinity of NCX. This decrease was smaller when the alpha2-isoform was downregulated (CHF) or inhibited (ouabain), indicating that the alpha2-isoform is necessary to modulate local [Na+]i close to NCX. CONCLUSION: Downregulation of the alpha2-isoform causes attenuated control of NCX activity in CHF, reducing its capability to extrude Ca2+ from cardiomyocytes.     

The Na+/K+-ATPase alpha2-isoform regulates cardiac contractility in rat cardiomyocytes

OBJECTIVE: The presence of both alpha1- and alpha2-isoforms of the Na+/K+-ATPase (NKA) in cardiomyocytes indicates different functions. We hypothesized that preferential localization of the alpha2-isoform to the t-tubules, locally controlling the Na+/Ca2+-exchanger (NCX), underlies a specific role in Ca2+ handling. METHODS: We studied NKA isoform distribution in isolated cardiomyocytes from Wistar rats using immunocytochemistry. NKA pump and NCX currents (I(pump) and I(NCX)) were measured in control and detubulated cardiomyocytes. Intracellular Na+ concentration [Na+]i was assessed with the fluorescent dye SBFI. RESULTS: The alpha2-isoform abundance was higher in the t-tubules than in the surface sarcolemma. We established that 0.3 microM ouabain specifically blocked the alpha2-isoform in isolated rat cardiomyocytes. This low concentration blocked 10.7+/-0.6% of I(pump) in control, but only 6.0+/-0.5% in detubulated cardiomyocytes. Moreover, measured and calculated alpha1-specific and alpha2-specific I(pump) in control (547+/-29 pA and 66 pA, respectively) and in detubulated cells (495+/-30 pA and 31 pA, respectively) showed that 53% of the alpha2-isoform, but only 9.5% of the alpha1-isoform, were localized to the t-tubules. Despite the small abundance of the alpha2-isoform (approximately 11% of total NKA), selective inhibition of this isoform induced a 40% increase in contractility in field stimulated cardiomyocytes, but no increase in global [Na+]i. However, inhibition of the alpha2-isoform increased I(NCX) indicating local subsarcolemmal accumulation of Na+ near NCX. CONCLUSIONS: The alpha2-isoform of the NKA is functionally coupled to the NCX and can regulate Ca2+ handling without changing global [Na+]i.     

The functional effect of adenoviral Na+/Ca2+ exchanger overexpression in rabbit myocytes depends on the activity of the Na+/K+-ATPase

OBJECTIVES: The functional consequences of Na+/Ca2+ exchanger (NCX) overexpression in heart failure have been controversially discussed. NCX function strongly depends on intracellular sodium which has been shown to be increased in heart failure. METHODS AND RESULTS: We investigated the Na+/K+-ATPase (NKA) inhibitor ouabain (0.5-16 micromol/l) in electrically stimulated, isotonically contracting adult rabbit cardiocytes overexpressing NCX after adenoviral gene transfer (Ad-NCX-GFP, 48 h culture time). Myocytes transfected with adenovirus encoding for green fluorescent protein (Ad-GFP) served as a control. Contractions were analyzed by video-edge detection. In the Ad-NCX-GFP group, the maximum inotropic response was significantly reduced by 50.7% (P<0.05). This was a result of an enhanced susceptibility to contracture after exposure to the drug (median concentration (25-75%): 4 (4-8) vs. 8 (6-16) micromol/l, P<0.05). When analyzing relaxation before contracture, the maximum relaxation velocity was reduced (0.15+/-0.04 vs. 0.27+/-0.04 microm/s, P<0.05) and the time from peak shortening to 90% of relaxation was increased (298+/-39 vs. 185+/-15 ms, P<0.05). No differences in systolic and diastolic parameters were observed with the Na+ channel modulator BDF9198 (1 micromol/l). CONCLUSIONS: Inhibition of NKA by ouabain induces a combined diastolic and systolic dysfunction in NCX overexpressing rabbit myocytes. This may be the consequence of cytoplasmic Ca2+ overload due to inhibition of forward mode or induction of reverse mode Na+/Ca2+ exchange. In end-stage failing human myocardium and during digitalis treatment this mechanism may be of major importance.     

Mouse Na+/K+-ATPase beta1-subunit has a K+-dependent cell adhesion activity for beta-GlcNAc-terminating glycans

A 48-kDa beta-N-acetylglucosamine (GlcNAc)-binding protein was isolated from mouse brain by GlcNAc-agarose column chromatography. The N-terminal amino acid residues showed the protein to be a mouse Na(+)/K(+)-ATPase beta1-subunit. When the recombinant FLAG-beta1-subunit expressed in Sf-9 cells was applied to a GlcNAc-agarose column, only the glycosylated 38- and 40-kDa proteins bound to the column. In the absence of KCl, little of the proteins bound to a GlcNAc-agarose column, but the 38- and 40-kDa proteins bound in the presence of KCl at concentrations above 1 mM. Immunohistochemical study showed that the beta1-subunit and GlcNAc-terminating oligosaccharides are at the cell contact sites. Inclusion of anti-beta1-subunit antibody or chitobiose in cell aggregation assays using mouse neural cells resulted in inhibition of cell aggregation. These results indicate that the Na(+)/K(+)-ATPase beta1-subunit is a potassium-dependent lectin that binds to GlcNAc-terminating oligosaccharides: it may be involved in neural cell interactions.     

Point Mutations of the RUNX1/AML1 Gene in Sporadic and Familial Myeloid Leukemias

The RUNX1/AML1 gene is known to be the most frequent target for chromosomal translocation in leukemia. In addition, recent studies have demonstrated point mutations in the RUNX1 gene as an another mode of genetic lesion resulting in leukemia. Of particular interest, sporadic point mutations of biallelic type are found in a tight association with either the acute myelogenous leukemia (AML) MO subtype or trisomy 21. Germline mutations give rise to a familial platelet disorder that results in a predisposition to acute myelogenous leukemia (FPD/AML). Most of the RUNX1 mutants were defective in DNA binding but still active in beta binding, a characteristic that is consistent with the 3-dimensional structural findings and may explain the dominant inhibitory effects. Although genuine haploinsufficiency of RUNX1 was observed in some cases, a greater majority of mutant RUNX1 proteins may also act in a dominant-negative manner, possibly creating a higher propensity for leukemia development. The stronger dominant-negative effect was also deduced to be the major mechanism of the chimeric genes created by chromosomal translocations. The decrement of RUNXI activity may be a common underlying cause for RUNX1-related leukemias. However, because these RUNX1 abnormalities per se are insufficient for leukemogenesis, cooperating genetic alteration(s) should be intensively sought for further mechanistic insights and future clinical applications.