Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Screening a rat colon cDNA library for aldosterone-induced genes resulted in the molecular cloning of a cDNA whose corresponding mRNA is strongly induced in the colon by dexamethasone, aldosterone, and a low NaCl diet. A similar mRNA was detected in kidney papilla but not in brain, heart, or skeletal muscle. Xenopus laevis oocytes injected with cRNA synthesized from this clone, designated CHIF (channel-inducing factor), express a K(+)-specific channel activity. The biophysical, pharmacological, and regulatory characteristics of this channel are very similar to those reported before for IsK (minK). These include: slow (tau > 20 s) activation by membrane depolarization with a threshold potential above -50 mV, blockade by clofilium, inhibition by phorbol ester, and activation by 8-bromoadenosine 3',5'-cyclic monophosphate and high cytoplasmic Ca2+. The primary structure of this clone, however, shows no homology to IsK. Instead, CHIF exhibits > 50% similarity to two other short bitopic membrane proteins, phospholemman and the gamma subunit of Na+K(+)-ATPase. The data are consistent with the possibility that CHIF is a member of a family of transmembrane regulators capable of activating endogenous oocyte transport proteins.
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PMID:A corticosteroid-induced gene expressing an "IsK-like" K+ channel activity in Xenopus oocytes. 759 86

Channel inducing factor (CHIF) is a novel cDNA recently cloned from a rat distal colon cDNA library of dexamethasone-treated animals. While its expression in Xenopus oocytes evokes a potassium channel activity similar to that induced by Isk (minK), its cellular role is not clear. CHIF exhibits significant homologies with proteins that are putatively regulatory (phospholemman, gamma-subunit of Na(+)-K(+)-ATPase, Mat-8) while it differs from the small-conductance potassium channel Isk. We have studied the tissue specificity of CHIF expression in rat by in situ hybridization. CHIF is selectively present in the distal parts of the nephron (medullary and papillary collecting ducts and end portions of cortical collecting tubule) and in the epithelial cells of the distal colon. No expression of CHIF was found in renal proximal tubule, loop of Henle and distal tubule, proximal colon, small intestine, lung, choroid plexus, salivary glands, or brain. To gain some insight into CHIF function, we have investigated, using in situ hybridization and ribonuclease protection assay, whether CHIF mRNA expression could be altered in some situations. In the distal colon, corticosteroid hormones, sodium restriction, low-potassium diet, and metabolic acidosis significantly increased CHIF mRNA expression. In the kidney, metabolic acidosis was the only condition that showed an increase in CHIF mRNA expression. Some of these treatments also altered the expression of the colonic H(+)-K(+)-ATPase mRNA. In summary, CHIF mRNA is selectively expressed in the medullary collecting duct of the kidney and in the epithelium of the distal colon; its expression varies differently in these two target tissues after alterations in corticosteroid status, potassium depletion, and metabolic acidosis. The precise cell-specific functions of CHIF remain to be established.
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PMID:Cellular localization and regulation of CHIF in kidney and colon. 884 4

Previous reports have demonstrated that the phospholemman (PLM), a 72-residue plasma-membrane protein enriched in skeletal muscle and heart, is a major substrate phosphorylated in response to insulin and adrenergic stimulation. Here we describe the isolation and characterization of human and rat PLM cDNA from the heart. Both PLM proteins share significant nucleotide and amino acid sequence and structural similarities with the previously published canine PLM and, to a lesser degree, with Na+/K(+)-ATPase gamma subunit, Mat-8 protein, and CHIF protein. Despite the functional diversity, all these proteins are quite small and possess a single transmembrane domain. Human PLM appears to be a unique gene localized on chromosome 19q13.1. The PLM mRNA is widely distributed in human tissues, with the highest expression in skeletal muscle and heart, suggesting a functional role in muscle contraction. Like canine PLM, both human and rat PLM induce a hyperpolarization-activated chloride current when expressed in Xenopus oocytes. The high degree of sequence and functional conservation among the mammalian PLM proteins indicates that this gene is conserved throughout evolution.
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PMID:Characterization of the human and rat phospholemman (PLM) cDNAs and localization of the human PLM gene to chromosome 19q13.1. 916 43

The molecular mechanisms by which corticosteroids affect fluid and electrolyte balance are unclear. Though glucocorticoid-responsive genes have been identified, genes regulated by aldosterone have not. CHIF (channel-inducing factor gene) is a recently identified gene that is up-regulated in the distal colon by chronic corticosteroid exposure, is expressed in the kidney, and induces a K+-specific current in Xenopus oocytes. The predicted protein shows similarity to gammaNa.K-ATPase, phospholemman, and Mat-8; all seem to be involved in ion transport. CHIF thus presents as a potential aldosterone target gene. In this study, CHIF expression was examined in rats in the acute timeframe of 0.5-4 h after corticosteroid administration. CHIF messenger RNA showed up-regulation by both mineralocorticoid and glucocorticoid receptor agonists in the distal colon, which was not diminished by cycloheximide. Corticosteroid regulation was not observed in the kidney. Basal and induced expression was absent in the lung and in all gastrointestinal tissues except colon, with expression increasing proximal to distal. CHIF is the first gene to show acute regulation by aldosterone and thus encodes a candidate aldosterone-induced protein. In addition, gammaNa.K-ATPase gene expression was found to be very low in colon and significantly higher in kidney. Regulation by corticosteroids was not evident in either tissue.
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PMID:Acute regulation by corticosteroids of channel-inducing factor gene messenger ribonucleic acid in the distal colon. 1006 46

P-type ATPases (E1E2-ATPases) are primary active transporters which form phospho-intermediates during their catalytic cycle. They are classified into P1 to P4 based on the primary structure and potential transmembrane segments. Although the classic P-type ATPases are cation transporters, two new members have recently been found; one is a flippase catalyzing the flip-flop movement of aminophospholipids, but the substrate and function of the other one remain unknown. It would be interesting to determine whether the cations and aminophospholipids are transported by similar or different mechanisms. P-type ATPases are believed to have been derived from a common ancestor, and their genes are found to be distributed in various chromosomal loci. However, gene duplication events can be traced from the tandem arrangement of genes and their linkage map. Na+/K+- and H+/K+-ATPases have not only closely related a subunits but also similar beta subunits. Renal Na+/K+-ATPase has an additional subunit gamma. Similar small polypeptides (phospholemman, Mat-8 and CHIF), which induce Cl- and K+ currents, have been found. The idea of their functional and structural coupling with P-type ATPases, especially with H+/K+-ATPase, is intriguing. Each P-type ATPase must have specific domains or sequences for its intracellular trafficking (sorting, retention and recycling). Identification of such regions and studies on the molecules playing role in their recognition may facilitate the unveiling of various cellular processes regulated by P-type ATPases.
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PMID:Structures of P-type transporting ATPases and chromosomal locations of their genes. 1020 33

A gene family of small membrane proteins, represented by phospholemman and the gamma subunit of Na,K-ATPase, was defined and characterized by the analysis of more than 1000 related ESTs (expressed sequence tags). In addition to new and more complete cDNA sequence for known family members (including MAT-8, CHIF, and RIC), the findings included two new family members and new splicing variants. A large number of EST replicates made it possible to derive curated DNA sequence with higher confidence and accuracy than from the sequencing of individual clones. The family has a core motif of 35 invariant and conserved amino acids centered on a single transmembrane span. Features of each predicted protein product were compared, and tissue distributions were determined. The gene family was named FXYD (pronounced fix-id) in recognition of invariant amino acids in its signature motif. The abundant proteins are involved in the control of ion transport.
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PMID:The FXYD gene family of small ion transport regulators or channels: cDNA sequence, protein signature sequence, and expression. 1095 Sep 25

The Na,K-ATPase provides the driving force for many ion transport processes through control of Na(+) and K(+) concentration gradients across the plasma membranes of animal cells. It is composed of two subunits, alpha and beta. In many tissues, predominantly in kidney, it is associated with a small ancillary component, the gamma-subunit that plays a modulatory role. A novel 15-kDa protein, sharing considerable homology to the gamma-subunit and to phospholemman (PLM) was identified in purified Na,K-ATPase preparations from rectal glands of the shark Squalus acanthias, but was absent in pig kidney preparations. This PLM-like protein from shark (PLMS) was found to be a substrate for both PKA and PKC. Antibodies to the Na, K-ATPase alpha-subunit coimmunoprecipitated PLMS. Purified PLMS also coimmunoprecipitated with the alpha-subunit of pig kidney Na, K-ATPase, indicating specific association with different alpha-isoforms. Finally, PLMS and the alpha-subunit were expressed in stoichiometric amounts in rectal gland membrane preparations. Incubation of membrane bound Na,K-ATPase with non-solubilizing concentrations of C(12)E(8) resulted in functional dissociation of PLMS from Na,K-ATPase and increased the hydrolytic activity. The same effects were observed after PKC phosphorylation of Na,K-ATPase membrane preparations. Thus, PLMS may function as a modulator of shark Na,K-ATPase in a way resembling the phospholamban regulation of the Ca-ATPase.
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PMID:Identification of a phospholemman-like protein from shark rectal glands. Evidence for indirect regulation of Na,K-ATPase by protein kinase c via a novel member of the FXYDY family. 1096 95

The (Na+,K+)-ATPase is a plasma membrane protein complex composed of at least three subunits (alpha,beta,gamma) that couples the exchange of three cytoplasmic Na+ ions with two extracellular K+ ions, to the hydrolysis of one molecule ofATP in most animal cells. The gamma-subunit is a 66 residue membrane protein associated with the active alpha/beta binary complex. It can be considered as an archetype of single transmembrane proteins (type I) which may play a modulatory role upon association with functional membrane partners. This paper highlights similar associations observed with other ATPases such as the sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA1/SERCA 2a), but also with Cl- and/or K+ currents, ionic channels (HERG, KCNQ1) and G-protein coupled receptors (adrenomedullin, CGRP and calcitonin) which are of particular interest in the cardiovascular field. Here is reviewed the assessed or suggested regulatory role of a family of small plasma/SR associated membrane proteins including gamma-subunit, phospholemman, Mat 8, KCNE (type 1, 2 and 3), RAMP (type 1, 2 and 3), sarcolipin and phospholamban, mainly found in muscular and vascular tissues. These proteins are critical in controlling important biological processes which derive from specific associations with a binding partner and particular subcellular localizations.
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PMID:The gamma-subunit of (Na+,K+)-ATPase: a representative example of human single transmembrane protein with a key regulatory role. 1135 3

1. The gamma subunit is a specific component of the plasmalemmal Na(+),K(+)-ATPase. Like structurally related single-spanning membrane proteins such as cardiac phospholemman, Mat-8 and renal CHIF, large ion conductances are activated when gamma subunits are expressed in Xenopus oocytes. 2. Here we report critical properties of the gamma-activated conductance. The gamma-activated conductance showed non-selective cationic and anionic permeation, and extremely slow kinetics, with an activation time constant > 1 s following steps to -100 mV. 3. The gamma-activated conductance was inhibited by extracellular divalent ions including Ba(2+) (K(i) = 0.7 mM) and Ca(2+) (K(i) = 0.4 mM). 4. 2-Deoxyglucose (MW approximately 180), inulin (MW approximately 5000) and spermidine (MW approximately 148) efflux could occur through the gamma-activated conductance pathway, indicating a large pore diameter. In contrast, dextran-70 (MW approximately 70 000) did not pass through the gamma-activated channel, indicating an upper limit to the pore size of approximately 50 A (5 nm). 5. Similar conductances that are permeable to large molecules were activated by extreme hyperpolarization (> -150 mV) of uninjected oocytes. 6. We conclude that the Na(+),K(+)-ATPase gamma subunits activate Ca(2+)- and voltage-gated, non-selective, large diameter pores that are intrinsically present within the oocyte membrane.
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PMID:Heterologous expression of the Na(+),K(+)-ATPase gamma subunit in Xenopus oocytes induces an endogenous, voltage-gated large diameter pore. 1153 33

The effects of phospholipid acyl chain length (n(c)) and cholesterol on Na,K-ATPase reconstituted into liposomes of defined lipid composition are described. The optimal hydrophobic thickness of the lipid bilayer decreases from n(c) = 22 to 18 in the presence of 40 mol% cholesterol. Hydrophobic matching as well as specific interactions of cholesterol with the phosphorylation/dephosphorylation reactions is found to be important. A novel regulatory protein has been identified in Na,K-ATPase membrane preparations from the shark (phospholemmanlike protein from shark, PLMS) with significant homology to phospholemman (PLM), the major protein kinase substrate in myocardium. Both are members of the FXYD gene family. Another member of this family is the Na,K-ATPase gamma subunit indicating that these proteins may be specific regulators of the Na,K-ATPase. A regulatory mechanism is described in which association/dissociation of PLMS with the Na,K-ATPase is governed by its phosphorylation by protein kinases.
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PMID:Modulation of Na,K-ATPase by associated small transmembrane regulatory proteins and by lipids. 1176 17


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