Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Dissociated rat superior cervical ganglion (SCG) neurons have been shown to possess a hyperpolarization-activated inwardly rectifying chloride current. The current was not altered by changes in external potassium concentration, replacing external cations with NMDG (N-methyl-D-glucamine) or by addition of 10 mM caesium or barium ions. 2. The reversal potential of the current was altered by changing external anions. The anion selectivity of the current was Cl- > Br- > I- > cyclamate. All substituted permeant anions also blocked the current. 3. The current was blocked by DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid), 9AC (anthracene-9-carboxylic acid) and NPPB (5-nitro-2-(3-phenylpropylamino)benzoic acid) but was unaffected by SITS (4-acetamido-4'-isothiocyanatostilbene- 2,2'-disulphonic acid) and niflumic acid. The effective blockers were voltage dependent; DIDS and NPPB were more effective at depolarized potentials while 9AC was more effective at hyperpolarized potentials. 4. The current was enhanced by extracellular acidification and reduced by extracellular alkalinization. Reducing external osmolarity was without effect in conventional whole-cell recording but enhanced current amplitude in those perforated-patch recordings where little current was evident in control external solution. 5. The current in SCG neurons was blocked by external cadmium and zinc. ClC-2 chloride currents expressed in Xenopus oocytes were also sensitive to block by these divalent ions and by DIDS but the sensitivity of ClC-2 to block by cadmium ions was lower than that of the current in SCG neurons. 6. Reverse transcriptase-polymerase chain reaction (RT-PCR) experiments showed the presence of mRNA for ClC-2 in SCG neurons but not in rat cerebellar granule cells which do not possess a hyperpolarization-activated Cl- current. 7. The data suggest that ClC-2 may be functionally expressed in rat SCG neurons. This current may play a role in regulating the internal chloride concentration in these neurons and hence their response to activation of GABAA receptors.
 ...
PMID:Characterization of the hyperpolarization-activated chloride current in dissociated rat sympathetic neurons. 950 29

The transport of lactate and pyruvate across membranes of vestibular dark cells (VDC) may be important under aerobic, ischemic or hypoxic conditions. This study addresses the questions whether VDC from the gerbil contain an H+/monocarboxylate- cotransporter (MCT) and in which membrane, apical or basolateral, MCT is located. Uptake of monocarboxylates into VDC was monitored in functional studies by measuring the cytosolic pH (pHi) and by measuring the pH-sensitive equivalent short circuit current (Isc). Subtypes of the functionally identified MCT which are present in vestibular labyrinth tissues were identified as transcripts by cloning and sequencing of reverse-transcriptase polymerase chain reaction (RT-PCR) products. Monocarboxylates but not dicarboxylates induced a transient acidification of pHi which was inhibited by 5 mM alpha-cyano-4-hydroxycinnamate (CHC) but not by 1 microM DIDS or 500 microM pCMBS. The initial rate of acidification induced by monocarboxylates was dose-dependent in the range between 1 and 20 mM. K(m) values were for pyruvate 1.3, acetate 3.7, L-lactate 3.8 and D-lactate 7.3 mM. Both apical and basolateral application of monocarboxylates caused a transient increase of Isc which was sensitive to 5 mM CHC. RT-PCR revealed the presence of transcripts for the MCT subtypes MCT1 and MCT2. The identity of transcripts was confirmed by sequence analysis. These observations suggest that VDC contain an MCT in their apical and basolateral membrane and that the vestibular labyrinth contains transcripts for the subtypes MCT1 and MCT2.
 ...
PMID:Vestibular dark cells contain an H+/monocarboxylate- cotransporter in their apical and basolateral membrane. 956 48

Fluid transport across cultures of bovine tracheal epithelium was measured with a capacitance probe technique. Baseline fluid absorption (Jv) across bovine cells of 3.2 microliter. cm-2. h-1 was inhibited by approximately 78% after 1 h of exposure to suspensions of Pseudomonas aeruginosa, with a concomitant decrease in transepithelial potential (TEP) and increase in transepithelial resistance (Rt). Effects of P. aeruginosa were blocked by amiloride, which decreased Jv by 112% from baseline of 2.35 +/- 1.25 microliter. cm-2. h-1, increased Rt by 101% from baseline of 610 +/- 257 Omega. cm2, and decreased TEP by 91% from baseline of -55 +/- 18.5 mV. Microelectrode studies suggested that effects of P. aeruginosa on amiloride-sensitive Na absorption were due in part to a block of basolateral membrane K channels. In the presence of Cl transport inhibitors [5-nitro-2-(3-phenylpropylamino)-benzoic acid, H2-DIDS, and bumetanide], P. aeruginosa induced a fluid secretion of approximately 2.5 +/- 0.4 microliter. cm-2. h-1 and decreased Rt without changing TEP. However, these changes were abolished when the transport inhibitors were used in a medium in which Cl was replaced by an impermeant organic anion. Filtrates of P. aeruginosa suspensions had no effect on Jv, TEP, or Rt. Mutants lacking exotoxin A or rhamnolipids or with defective lipopolysaccharide still inhibited fluid absorption and altered bioelectrical properties. By contrast, mutations in the rpoN gene encoding a sigma factor of RNA polymerase abolished actions of P. aeruginosa. In vivo, changes in transepithelial salt and water transport induced by P. aeruginosa may alter viscosity and ionic composition of airway secretions so as to foster further bacterial colonization.
 ...
PMID:Pseudomonas aeruginosa induces changes in fluid transport across airway surface epithelia. 981 77

Anion exchangers (AE) are transmembrane proteins catalyzing electroneutral exchange of Cl(-) for HCO3-. To date, three different genes coding for this protein, AE1, AE2 and AE3, have been identified in many species. AE1 is considered to be the unique anion exchanger expressed in erythrocytes. In this paper we propose the presence of three different AEs in skate erythrocytes, a skAE1, a skAE2 and a skAE3, cloned by RT-PCR (reverse-transcriptase polymerase chain reaction). These three skAE have a similar predicted secondary structure. All three skAE are divided in two main domains: a hydrophilic cytoplasmic N-terminal domain and a C-terminal domain crossing the lipid bilayer at least 12 times. The greatest similarity is found in the membrane-spanning domain of the three skAE. The size as well as the amino-acid sequence of the cytoplasmic domain differ significantly among three anion exchangers. Functional expression studies in Xenopus oocytes led to the conclusion that skAE-1 and -2 share some functional features (Cl-dependence and DIDS sensitivity). The skAE3 could not be expressed in Xenopus oocytes. These data are in agreement with expression data obtained with AEs of different species utilizing the oocyte system. It is highly probable that these three new AE sequences come from three different genes, thus suggesting for the first time the presence of the three AE genes in Chondrichthyes.
 ...
PMID:Evidence for the presence of three different anion exchangers in a red cell. Functional expression studies in Xenopus oocytes. 1287 59