Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P41181 (collecting duct)
 5,183 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activity of apical K(+) channels in cortical collecting duct (CCD) is stimulated and inhibited by protein kinase A (PKA) and C (PKC), respectively. Direct interaction between phosphatidylinositol 4,5-bisphosphate (PIP(2)) and the cloned CCD K(+) channel, ROMK1, is critical for channel opening. We have found previously that phosphorylation of ROMK1 by PKA increases affinity of the channel for PIP(2) and mutation of PKA sites reduces the affinity of ROMK1 for PIP(2). In this study we investigate the molecular mechanism for PKC regulation of ROMK and report that mutants of ROMK1 with reduced PIP(2) affinity exhibit an increased sensitivity to inhibition by phorbol myristate acetate (PMA). The effect of PMA can be prevented by pretreatment with calphostin-C. Activation of PKC by carbachol in Xenopus oocytes co-expressing M1 muscarinic receptors also causes inhibition of the channels. Calphostin-C prevents carbachol-induced inhibition, suggesting that activation of PKC is necessary for inhibition of the channels. PMA reduces open probability of the channel in cell-attached patch clamp recordings. After inhibition by PMA in cell-attached recordings, application of PIP(2) to the cytoplasmic face of excised inside-out membranes restores channel activity. PMA reduces PIP(2) content in oocyte membrane and calphostin-C prevents the reduction. These results suggest that reduction of membrane PIP(2) content contributes to the inhibition of ROMK1 channels by PKC. This mechanism may underscore the inhibition of K(+) secretion in CCD by hormones that activate PKC.
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PMID:Protein kinase C inhibits ROMK1 channel activity via a phosphatidylinositol 4,5-bisphosphate-dependent mechanism. 1261 24

Whole cell voltage clamp experiments were performed in a mouse cortical collecting duct principal cell line using patch pipettes back-filled with a solution containing phosphatidylinositol 3,4,5-trisphosphate (PIP(3)). PIP(3) significantly increased amiloridesensitive current in control cells but not in the cells prestimulated by aldosterone. Additionally, aldosterone stimulated amiloridesensitive current in control cells, but not in the cells that expressed a PIP(3)-binding protein (Grp1-PH), which sequestered intracellular PIP(3). 12 amino acids from the N-terminal tail (APGEKIKAKIKK) of gamma-epithelial sodium channel (gamma-ENaC) were truncated by PCRbased mutagenesis (gammaT-ENaC). Whole cell and confocal microscopy experiments were conducted in Madin-Darby canine kidney cells co-expressing alpha- and beta-ENaC only or with either gamma-ENaC or gamma(T)-ENaC. The data demonstrated that the N-terminal tail truncation significantly decreased amiloride-sensitive current and that both the N-terminal tail truncation and LY-294002 (a PI3K inhibitor) prevented ENaC translocation to the plasmamembrane. These data suggest that PIP(3) mediates aldosterone-induced ENaC activity and trafficking and that the N-terminal tail of gamma-ENaC is necessary for channel trafficking, probably channel gating as well. Additionally, we demonstrated a novel interaction between gamma-ENaC and PIP(3).
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PMID:Phosphatidylinositol 3,4,5-trisphosphate mediates aldosterone stimulation of epithelial sodium channel (ENaC) and interacts with gamma-ENaC. 1620 29

Epithelial Sodium Channels (ENaCs) are expressed in different organs and tissues, particularly in the cortical collecting duct (CCD) in the kidney, where they fine tune sodium reabsorption. Dynamic rearrangements of the cytoskeleton are one of the common mechanisms of ENaC activity regulation. In our previous studies, we showed that the actin-binding proteins cortactin and Arp2/3 complex are involved in the cytoskeleton-dependent regulation of ENaC and that their cooperative work decreases a channel's probability of remaining open; however, the specific mechanism of interaction between actin-binding proteins and ENaC is unclear. In this study, we propose a new component for the protein machinery involved in the regulation of ENaC, the missing-in-metastasis (MIM) protein. The MIM protein contains an IMD domain (for interaction with PIP2 -rich plasma membrane regions and Rac GTPases; this domain also possesses F-actin bundling activity), a PRD domain (for interaction with cortactin), and a WH2 domain (interaction with G-actin). The patch-clamp electrophysiological technique in whole-cell configuration was used to test the involvement of MIM in the actin-dependent regulation of ENaC. Co-transfection of ENaC subunits with the wild-type MIM protein (or its mutant forms) caused a significant reduction in ENaC-mediated integral ion currents. The analysis of the F-actin structure after the transfection of MIM plasmids showed the important role played by the domains PRD and WH2 of the MIM protein in cytoskeletal rearrangements. These results suggest that the MIM protein may be a part of the complex of actin-binding proteins which is responsible for the actin-dependent regulation of ENaC in the CCD.
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PMID:Role of the Scaffold Protein MIM in the Actin-Dependent Regulation of Epithelial Sodium Channels (ENaC). 3011 21