Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01185 (vasopressin)
 23,126 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Arginine vasopressin (antidiuretic hormone, ADH) stimulation of sodium transport in high electrical resistance epithelia is accompanied by adenylate cyclase stimulation and cAMP accumulation. The hypothesis of direct phosphorylation of the purified amiloride-blockable epithelial Na+ channel protein by cAMP-dependent protein kinase A after ADH treatment of cultured cells was investigated in this study. Phosphate-depleted A6 cells (a cell line derived from toad kidney) were exposed to 32PO4(3-) in the absence or presence of basolateral ADH (100 milliunits/ml). After 20 min (the time needed for ADH to increase maximally Na+ transport), the Na+ channels were extracted from the cells and purified. At every stage of purification, only one subunit of the Na+ channel, namely, the 315-kDa subunit, was specifically phosphorylated as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography or scintillation counting. In addition, a polyclonal antibody raised against purified epithelial Na+ channel protein was able to immunoprecipitate the phosphorylated channel protein from a detergent-solubilized fraction of vasopressin-treated A6 cells. This same subunit was also specifically phosphorylated in vitro when the purified Na+ channel protein was incubated with gamma-[32P]ATP and the purified catalytic subunit of the cAMP-dependent protein kinase. Thus, only a single component, the 315-kDa subunit, of the Na+ channel protein complex (which is composed of six subunits) can be phosphorylated both in vivo and in vitro. This subunit is selectively phosphorylated by the catalytic subunit of cAMP-dependent protein kinase to a level of 2-3 mol of 32P/mol of protein.
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PMID:Phosphorylation of a single subunit of the epithelial Na+ channel protein following vasopressin treatment of A6 cells. 245 53

This study sought to elucidate the molecular mechanism involved in the Na+ entry across the apical membrane of the urinary bladder of the toad. Na+ transport, as measured by short-circuit current (SCC), was irreversibly inhibited by three tyrosine-specific reagents: N-acetylimidazole (ID50, 4.6 x 10(-2)M), tetranitromethane (1.8 x 10(-4) M), and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl; 3.4 x 10(-5) M). The functional specificity of NBD-Cl to block Na+ entry via Na+ channels was attested by the following: 1) NBD-Cl produced comparable inhibition of SCC and Na+ influx under aerobic and anaerobic conditions; 2) amphotericin B produced complete recovery of inhibited SCC; 3) vasopressin increased SCC only in proportion to the uninhibited SCC; 4) Km for Na+ was not changed; and 5) the half time for the inhibition varied as a function of amiloride concentration or pharmacologic activity of its analogues. On the basis of the above findings, these tyrosine-specific reagents are believed to be useful chemical probes for the identification and characterization of Na+ channel protein.
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PMID:Covalent modification and inhibition of an epithelial sodium channel by tyrosine-reactive reagents. 625 71

The early increase in luminal membrane Na+ permeability by aldosterone in Na(+)-reabsorbing epithelia is attributed to an increase in the open probability (and number) of preexisting amiloride-sensitive Na+ channels. Carboxyl methylation reactions are involved, but the mechanism of action is unknown. We report that the 90-95-kDa polypeptide subunit of a purified renal Na+ channel protein can be specifically carboxymethylated and that this biochemical reaction, in the presence of guanosine 5'-3-O-(thio)triphosphate, leads directly to an increase in channel activity. Further, we show that protein kinase A-mediated phosphorylation can synergistically activate these channels. We suggest that renal Na+ channels have multiple biochemical regulatory inputs and that post-translational modifications underlie the increases in luminal membrane Na+ channel activity produced by aldosterone and vasopressin in Na(+)-reabsorbing epithelia.
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PMID:Carboxyl methylation activates purified renal amiloride-sensitive Na+ channels in planar lipid bilayers. 807 43

To determine the mechanism by which vasopressin increases apical membrane Na+ entry, we evaluated whether or not this hormone could recruit Na+ channels from a subapical membrane pool using specific polyclonal antibodies raised against high amiloride affinity bovine renal papillary Na+ channels. We also studied the effect of protein kinase A (PKA)-mediated phosphorylation on single-channel activity of highly purified Na+ channels incorporated into planar lipid bilayer membranes. PKA induced a significant increase in open-channel probability (Po) with no change in single-channel conductance. As shown previously and reconfirmed in the present work, PKA catalyzed the phosphorylation of a single subunit of this Na+ channel protein, namely, a 300-kDa polypeptide. On the other hand, protein kinase C, in combination with diacylglycerol, Ca2+, and phosphatidylserine, phosphorylated both the 130- and 55-kDa subunits of this purified Na+ channel, with a concomitant decrease in Po of both untreated and previously PKA-treated channels. We also found, in expression studies conducted in confluent monolayers of amphibian renal A6 cells, that vasopressin did not induce the apical insertion of new channel proteins. These observations support the hypothesis that vasopressin increases the apical Na+ permeability by activating Na+ channels already resident in the apical membrane by a direct phosphorylation mechanism rather than by cytoplasmic recruitment of latent Na+ channels.
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PMID:Regulation by phosphorylation of purified epithelial Na+ channels in planar lipid bilayers. 839 86

The human neonatal period is characterized by renal immaturity with impaired capacity to regulate water and sodium homeostasis, resembling partial aldosterone resistance. Because aldosterone effects are mediated by the mineralocorticoid receptor (MR), we postulated that this hormonal unresponsiveness could be related to low MR expression in the distal nephron. We measured aldosterone and renin levels in umbilical cord blood of healthy newborns. We used quantitative real-time PCR and immunohistochemistry to analyze the expression of MR and key players of the mineralocorticoid signaling pathway during human and mouse renal development. High aldosterone and renin levels were found at birth. MR mRNA was detected in mouse kidney at d 16 postcoitum, peaking at d 18 postcoitum, but its expression was surprisingly very low at birth, rising progressively afterward. Similar biphasic temporal expression was observed during human renal embryogenesis, with a transient expression between 15 and 24 wk of gestation but an undetectable immunoreactive MR in late gestational and neonatal kidneys. This cyclic MR expression was tightly correlated with the evolution of the 11beta-hydroxysteroid dehydrogenase type 2 and the epithelial sodium channel alpha-subunit. In contrast, glucocorticoid and vasopressin receptors and aquaporin 2 followed a progressive and sustained evolution during renal maturation. Our study provides the first evidence for a low renal MR expression level at birth, despite high aldosterone levels, which could account for compromised postnatal sodium handling. Elucidation of regulatory mechanisms governing MR expression should lead to new strategies for the management of sodium waste in preterms and neonates.
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PMID:Low renal mineralocorticoid receptor expression at birth contributes to partial aldosterone resistance in neonates. 1947 42