Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004352 (autism)
 32,579 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Membrane vesicles, isolated after osmotic shock of synaptosomal rat brain fractions, actively accumulate L-glutamate. This process requires the presence of external sodium ions and internal potassium ions and is driven by artifically imposed ion gradients as the sole energy source. Either an Na+ gradient (out is greater than in) or a K+ gradient (in is greater than out) or both can be utilized to concentrate L-glutamate inside the vesicles. Transport is enhanced by valinomycin or by external thiocyanate ions and is about 50% inhibited by the proton ionophore carbonyl cyanide m-chlorophenylhydrazone. This transport thus appears to be stimulated by a membrane potential (interior negative). The glutamate transporter, the Km of which has been determined to be 3 micrometer, is specific for L-glutamate. The transport process is unaffected by ouabain but is strongly inhibited by p-hydroxymercuribenzoate as well as by nigericin, which collapses the energizing ion gradients across this membrane. Unlike the sodium dependent, but potassium independent active accumulation of gamma-aminobutyric acid in these vesicles (Kanner, B.I. (1978) Biochemistry 17, 1207) active L-glutamate uptake is not dependent on the presence of small monovalent anions in the external medium. The results provide direct evidence for Na+-coupled electrogenic active L-glutamate transport by rat brain membrane vesicles. The dependence on internal potassium ions is discussed.
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PMID:Active transport of L-glutamate by membrane vesicles isolated from rat brain. 70 89

Antibodies were raised against synthetic peptides corresponding to several regions of the rat brain gamma-aminobutyric acid (GABA) transporter. According to our model, this glycoprotein has 12 transmembrane alpha-helices with both amino and carboxyl termini located in the cytoplasm. The antibodies recognized the intact transporter on Western blots. Upon papain treatment, a reconstitutively active transporter can be isolated upon lectin chromatography (Kanner, B. I., Keynan, S., and Radian, R. (1989) Biochemistry 28, 3722-3728). The papainized transporter runs on sodium dodecyl sulfate-polyacrylamide gels as a broad band with an apparent molecular mass between about 58 and 68 kDa as compared to 80 kDa for the untreated transporter. The transporter fragment was recognized by all the antibodies, except for that raised against the amino terminus. Pronase cleaves the transporter to a relatively sharp 60-kDa band, which reacts with the antibodies against the internal loops but not with either the amino- or the carboxyl-terminal. This pronase-treated transporter, upon isolation by lectin chromatography, was reconstituted. It exhibits full GABA transport activity. This activity exhibits the same features as the intact system including an absolute dependence on sodium and chloride as well as electrogenicity. We conclude that the amino- and carboxyl-terminal parts of the transporter, possibly including transmembrane alpha-helices 1, 2, and 12, are not required for the transport function.
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PMID:Neither amino nor carboxyl termini are required for function of the sodium- and chloride-coupled gamma-aminobutyric acid transporter from rat brain. 173 54

A long-term follow-up study of 42 patients with West syndrome treated with high doses of sodium valproate is presented. Control of the hypsarrhythmic EEG pattern was achieved after two weeks for over three-quarters of the patients with sodium valproate doses of 100 to 300mg/kg/day. Recurrence of hypsarrhythmia was observed most often in patients treated with doses lower than 200mg/kg/day. Other types of seizures appeared in half of the patients followed beyond two years of age. Monotherapy throughout follow-up was possible for 30 patients. Autism occurred in only one infant, and 12 achieved normal mental status. The most common side-effects were asymptomatic thrombocytopenia, vomiting and mild somnolence. Hepatic enzymes were not altered.
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PMID:Infantile spasms treated with high doses of sodium valproate: initial response and follow-up. 187 25

The bovine heart F0F1-ATPase preparation (Serrano, R., Kanner, B., and Racker, E. (1976) J. Biol. Chem. 251, 2453-2461) has been further delipidated. The lipid-deficient preparation contained 2.5 mol of cardiolipin, 1 mol of phosphatidylcholine (PC), and 1 mol of phosphatidylethanolamine (PE) per mol of F0F1. When reconstituted with asolectin the delipidated preparation exhibited an activity of 13 mumol of ATP hydrolyzed/min/mg of protein which was 88% oligomycin-sensitive. The phospholipids in this preparation were analyzed by 31P NMR spectroscopy to determine if they were immobilized by the enzyme (rendered NMR-invisible). The PC and PE were below the limits of detection under the conditions utilized and the cardiolipin was NMR-invisible until the enzyme was denatured by addition of either 1% sodium dodecyl sulfate or 8 M urea. Addition of cardiolipin to the delipidated preparation and subsequent analysis by NMR spectroscopy revealed that approximately 4 mol of cardiolipin were immobilized per mol of F0F1 ATPase. The enzyme appears to have high affinity for cardiolipin exclusively, since PC (a prominent inner membrane lipid), phosphatidyl serine (an acidic phospholipid), and phosphatidyl glycerol (the precursor to cardiolipin) were not immobilized (rendered NMR-invisible) when added to the delipidated preparation.
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PMID:Tightly associated cardiolipin in the bovine heart mitochondrial ATP synthase as analyzed by 31P nuclear magnetic resonance spectroscopy. 214 80

The reconstruction of the purified sodium- and chloride-coupled gamma-aminobutyric acid transporter from rat brain into asolectin liposomes requires the addition of brain lipids (Radian, R., and Kanner, B. I. (1985) J. Biol. Chem. 260, 11859-11865). The reconstitution assay was used to identify the component(s) from brain lipids responsible for the stimulation during the fractionation of brain lipids. The distribution of the active component was found to be similar to that of cholesterol. Furthermore, cholesterol was found to mimic the effect of brain lipids and it stimulated the transport activity up to 20-fold. Optimal reconstituted transport activity was achieved with mixtures of cholesterol and any one of several phospholipids, such as phosphatidylcholine, phosphatidylserine or phosphatidylglycerol. gamma-Aminobutyric acid transport in these liposomes of defined composition exhibited all the properties of the native transporter, such as the absolute dependence on sodium and chloride and electrogenicity. Cholesterol could not be replaced by cholest-4-en-3one and other steroids, and thus its effect is probably not due to effects on membrane fluidity. The requirement was also not due to effects on intactness of the liposomes or incorporation of proteins into them. Furthermore it was found that the reconstitution of the sodium and potassium coupled L-glutamic acid transporter from rat brain also required cholesterol. However, in this case the optimal activity was reached by 4-5-fold lower levels of cholesterol than those necessary for gamma-aminobutyric acid transport. When cholesterol depletion from the transporters was incomplete, addition of exogenous brain lipids was not required. Thus, if the cholesterol was still associated with the transporter proteins, its final concentration, as a fraction of the total lipids present in the reconstitution mixture, was only about 0.01 mol%. Thus, it is likely that the effects of cholesterol are due to direct interactions with the cotransporters and not to an average effect on membrane properties.
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PMID:Cholesterol is required for the reconstruction of the sodium- and chloride-coupled, gamma-aminobutyric acid transporter from rat brain. 231 45

The sodium- and chloride-coupled gamma-aminobutyric transporter, an 80-kDa glycoprotein, has been subjected to deglycosylation and limited proteolysis. The treatment of the 80-kDa band with endoglycosidase F results in its disappearance and reveals the presence of a polypeptide with an apparent molecular mass of about 60 kDa, which is devoid of 125I-labeled wheat germ agglutinin binding activity but is nevertheless recognized by the antibodies against the 80-kDa band. Upon limited proteolysis with papain or Pronase, the 80-kDa band was degraded to one with an apparent molecular mass of about 60 kDa. This polypeptide still contains the 125I-labeled wheat germ agglutinin binding activity but is not recognized by the antibody. The effect of proteolysis on function was examined. The transporter was purified by use of all steps except that for the lectin chromatography [Radian, R., Bendahan, A., & Kanner, B.I. (1986) J. Biol. Chem. 261, 15437-15441]. After papain treatment and lectin chromatography, gamma-aminobutyric transport activity was eluted with N-acetylglucosamine. The characteristics of transport were the same as those of the pure transporter, but the preparation contained instead of the 80-kDa polypeptide two fragments of about 66 and 60 kDa. The ability of the anti-80-kDa antibody to recognize these fragments was relatively low. The observations indicate that the transporter contains exposed domains which are not important for function.
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PMID:Structural and functional studies on the sodium- and chloride-coupled gamma-aminobutyric acid transporter: deglycosylation and limited proteolysis. 250 69

The association of different phospholipids with a lipid-depleted oligomycin-sensitive ATPase from bovine cardiac mitochondria [Serrano, Kanner & Racker (1976) J. Biol. Chem. 251, 2453-2461] has been examined using three approaches. First, reconstitution of the ATPase with different synthetic diacyl phospholipids resulted in a 2-10-fold stimulation of ATPase specific activity depending upon the particular phospholipid employed. The phospholipid headgroup region displayed the following order of ATPase reactivation potential: dioleoylphosphatidylglycerol greater than dioleoylphosphatidic acid greater than dioleoylphosphatidylcholine. Furthermore, the ATPase showed higher levels of specific activity when reconstituted with dioleoyl phospholipid derivatives compared with dimyristoyl derivatives. Second, examination of the phospholipid remaining associated with the lipid-depleted ATPase upon purification showed that phosphatidylcholine, phosphatidylethanolamine, and diphosphatidylglycerol were present. No relative enrichment of any of these phospholipids (compared with their distribution in submitochondrial particles) was noted. Therefore, no preferential association between the ATPase and any one phospholipid could be found in the mitochondrial ATPase. Third, the sodium cholate-mediated phospholipid exchange procedure was employed for studying the phospholipid requirements of the ATPase. Replacement of about 50% of the mitochondrial phospholipid remaining with the lipid-depleted ATPase could be achieved utilizing either synthetic phosphatidic acid or phosphatidylcholine. Examination of the displaced mitochondrial phospholipid showed that phosphatidylcholine, phosphatidylethanolamine, and diphosphatidylglycerol were replaced with equal facility.
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PMID:Phospholipid association with the bovine cardiac mitochondrial adenosine triphosphatase. 315 84

Transport of gamma-aminobutyric acid (GABA) is electrogenic and completely depends on the presence of both sodium and chloride ions. These ions appear to be cotransported with gamma-aminobutyric acid through its transporter [reviewed in Kanner, B. I. (1983) Biochim. Biophys. Acta 726, 293-316]. Using proteoliposomes into which a partially purified gamma-aminobutyric acid transporter preparation was reconstituted, we have been able--for the first time--to provide direct evidence for sodium- and chloride-coupled gamma-aminobutyric acid transport. This has been done by measuring the fluxes of 22Na+, 36Cl-, and [3H]GABA. These fluxes have the following characteristics: There are components of the net fluxes of sodium and chloride that are gamma-aminobutyric acid dependent. The sodium flux is chloride dependent; i.e., when Cl- is replaced by inorganic phosphate or by SO4(2-), gamma-aminobutyric acid dependent sodium fluxes are abolished. The chloride flux is sodium dependent; i.e., when Na+ is replaced by Tris+ or by Li+, gamma-aminobutyric acid dependent chloride fluxes are abolished. Thus, the gamma-aminobutyric acid dependent sodium and chloride fluxes appear to be catalyzed by the transporter. Using these fluxes we have attempted to determine the stoichiometry of the process. We measured the initial rate of sodium-dependent gamma-aminobutyric acid fluxes and that of gamma-aminobutyric acid dependent sodium fluxes. This yields the stoichiometry between sodium and gamma-aminobutyric acid (2.58 +/- 0.99). Similarly, we measured the stoichiometry between chloride and gamma-aminobutyric acid, which is found to be 1.27 +/- 0.12.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:gamma-Aminobutyric acid transport in reconstituted preparations from rat brain: coupled sodium and chloride fluxes. 334 23

Using the reconstitution conditions developed recently (Radian, R., and Kanner, B. I. (1985) J. Biol. Chem. 260, 11859-11865) we have now purified the sodium- and chloride-coupled gamma-aminobutyric acid transporter from rat brain to apparent homogeneity. A partially purified transporter preparation was passed over wheat germ agglutinin-Sepharose 6MB and non-bound proteins were washed away. The transport activity, as expressed upon reconstitution of the protein into liposomes, was eluted by a solution containing Triton X-100 and N-acetylglucosamine. The specific transport activity was increased almost 400-fold over that of the crude extract. Taking into account an approximately 2.5-fold inactivation during the lectin column chromatography, the actual purification is about 1000-fold. Sodium dodecyl sulfate-polyacrylamide electrophoresis of the active fractions revealed one band of 80 kDa and small amounts of a band which ran at an apparent molecular mass of 160 kDa. The ratio between the two could be experimentally changed such as, for instance, by lyophilization. Polyclonal antibodies were prepared against the 80-kDa band which also cross-reacted with the 160-kDa band, indicating that the latter apparently represents a dimer form of the first. Using Protein A-Sepharose Cl-4B and the antibody against the 80-kDa band, we were able to quantitatively immunoprecipitate the potential gamma-aminobutyric acid transport activity from a crude transporter preparation. The pure transporter preparation exhibited the same features of the transporter in synaptic plasma membrane vesicles, namely dependence on sodium and chloride, electrogeneity, affinity, and efflux and exchange properties. We conclude that the 80-kDa band represents the gamma-aminobutyric acid transporter.
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PMID:Purification and identification of the functional sodium- and chloride-coupled gamma-aminobutyric acid transport glycoprotein from rat brain. 353 2

It is currently thought that aggregation of the receptor for immunoglobulin E on mast cells, basophils, and a tumor analog, rat basophilic leukemia (RBL) cells, induces an enhanced permeability of the plasma membrane to calcium, thereby initiating degranulation of the cells. Even in the absence of calcium ions, aggregation of the receptor causes depolarization of the plasma membrane (Kanner, B. I., and Metzger, H. (1983) Proc. Natl. Acad. Sci. U. S. A. 80, 5744-5748), suggesting that other ions can traverse the putative channel. Direct evidence for this now has been obtained with measurements of increased 22Na+ fluxes in the absence of calcium ions, induced by aggregation of receptors. This reaction was optimally studied in the presence of ouabain. When aggregation of the receptor was induced by reacting the cell-bound IgE with a multivalent antigen, the sodium flux was completely inhibited by univalent hapten. The sodium flux was also completely inhibited by 2 mM calcium. Aggregation-induced 45Ca2+ fluxes were observed in the presence of millimolar concentrations of external Ca2+, but not in its absence. Depolarization of the plasma membrane potential by the addition of potassium to the medium in the presence of calcium did not itself induce degranulation. In fact, aggregation of the receptors for IgE in the presence of high external potassium resulted in a greatly diminished degranulation. These data indicate that the ion channel modulated by aggregation of receptor differs from the voltage-dependent type of calcium channels. We suggest that in the absence of calcium this channel is rather unspecific, but that calcium can modify it to become calcium selective.
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PMID:Initial characterization of the calcium channel activated by the cross-linking of the receptors for immunoglobulin E. 608 86


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