Functional and structural characterization of PKA-mediated pHi gating of ROMK1 channels.
J Mol Graph Model
; 27(3): 332-41, 2008 Oct.
Article
em En
| MEDLINE
| ID: mdl-18620882
ABSTRACT
Hyperprostaglandin E syndrome/antenatal Bartter syndrome (HPS/aBS) is a severe salt-losing renal tubular disorder and results from the mutation of renal outer medullary K(+) (ROMK1) channels. The aberrant ROMK1 function induces alterations in intracellular pH (pH(i)) gating under physiological conditions. We investigate the role of protein kinase A (PKA) in the pH(i) gating of ROMK1 channels. Using giant patch clamp with Xenopus oocytes expressing wild-type and mutant ROMK1 channels, PKA-mediated phosphorylation decreased the sensitivity of ROMK1 channels to pH(i). A homology model of ROMK1 reveals that a PKA phosphorylation site (S219) is spatially juxtaposed to the phosphatidylinositol 4,5-bisphosphate (PIP(2)) binding residues (R188, R217, and K218). Molecular dynamics simulations suggest a stable transition state, in which the shortening of distance between S219 and R217 and the movement of K218 towards the membrane after the PKA-phosphorylation can be observed. Such conformational change may bring the PIP(2) binding residues (K218) more accessible to the membrane-bound PIP(2). In addition, PIP(2) dose-dependently reactivates the acidification-induced rundown channels only when ROMK1 channels have been phosphorylated by PKA. This implies a sequence regulatory episode reflecting the role of PIP(2) in the pH(i) gating of ROMK1 channels by PKA-mediated phosphorylation. Our results provide new insights into the molecular mechanisms underlying the ROMK1 channel regulation associated with HPS/aBS.
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1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Ativação do Canal Iônico
/
Proteínas Quinases Dependentes de AMP Cíclico
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Canais de Potássio Corretores do Fluxo de Internalização
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Espaço Intracelular
Limite:
Animals
Idioma:
En
Revista:
J Mol Graph Model
Ano de publicação:
2008
Tipo de documento:
Article