Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Renal secretion of organic cations involves at least two distinct transporters, located in the basolateral and apical membranes of proximal tubule cells. Whereas the basolateral transporter has recently been cloned, sequence information about the apical type was not yet available. An organic cation transporter, OCT2p, was cloned from LLC-PK1 cells, a porcine cell line with properties of proximal tubular epithelial cells. OCT2p was heterologously expressed and characterized in human embryonic kidney 293 cells. OCT2p-mediated uptake of the prototypical organic cation [14C]tetraethylammonium ([14C]TEA) into 293 cells was saturable. There was a highly significant correlation between the Ki values for the inhibition of apical [14C]TEA uptake into LLC-PK1 cells and 293 cells transfected with OCT2p (r = 0.995; p < 0.001; n = 6). Although OCT2p is structurally related to OCT1r, the basolateral organic cation transporter from rat kidney, the transporters could be clearly discriminated pharmacologically with corticosterone, decynium22, and O-methylisoprenaline. The findings at hand suggest that OCT2 corresponds to the apical type of organic cation transporter. Reverse transcriptase-polymerase chain reaction indicates that mRNA of OCT1r is limited to non-neuronal tissue, whereas OCT2r, the OCT2p homologue from rat, was found in both the kidney and central nervous regions known to be rich in the monoamine transmitter dopamine.
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PMID:Primary structure and functional expression of the apical organic cation transporter from kidney epithelial LLC-PK1 cells. 909 81

The influence of activation of glutamate receptor (GluR) on outward K(+) current in cultured neonate rat hippocampal astrocytes was investigated. Patch-clamp analysis of K(+) channel currents in cultured astrocytes identified the existence of 71 +/- 6 and 161 +/- 11 pS single-channel K(+) currents that were sensitive to changes in voltage and [Ca(2+)](i) and blocked by external TEA but not by charybdotoxin, iberiotoxin, apamin, or 4-aminopyridine. Reverse transcriptase (RT)-PCR and Northern blot analysis revealed transcripts of the Ca(2+)-activated K(+) channel (K(Ca)) beta(4)-subunit (beta4) (KCNMB4) in cultured astrocytes. Expression of the metabotropic glutamate receptor (mGluR) subtypes mGluR1 and mGluR5 and the ionotropic glutamate receptor (iGluR) subtypes iGluR1 and iGluR4 were detected by RT-PCR and immunofluorescence analysis in cultured astrocytes. The mGluR agonists L-glutamate and quisqualate increased the open state probability (NP(o)) of the 71 and 161 pS K(+) channel currents that were prevented by the mGluR receptor antagonists 1-aminoindan-1,5-dicarboxylic acid or L-(+)-2-amino-3-phosphonopropionic acid and not by the iGluR antagonists (+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate or CNQX. Activation of the two types of K(+) channel currents by mGluR agonists was attenuated by pertussis toxin and by inhibition of phospholipase C (PLC) or cytochrome P450 arachidonate epoxygenase. These results indicate that brain astrocytes contain the KCNMB4 transcript and express two novel types of K(Ca) channels that are gated by activation of a G-protein coupled metabotropic glutamate receptor functionally linked to PLC and cytochrome P450 arachidonate epoxygenase activity.
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PMID:Metabotropic glutamate receptor activation enhances the activities of two types of Ca2+-activated k+ channels in rat hippocampal astrocytes. 1262 72