| Autor: |
Inderwiedenstraße L; Department for Cellular and Translational Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, 44801, Bochum, Germany., Kienitz MC; Department for Cellular and Translational Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, 44801, Bochum, Germany. cecile.kienitz@ruhr-uni-bochum.de. |
| Jazyk: |
angličtina |
| Zdroj: |
Pflugers Archiv : European journal of physiology [Pflugers Arch] 2024 Jul; Vol. 476 (7), pp. 1041-1064. Date of Electronic Publication: 2024 Apr 24. |
| DOI: |
10.1007/s00424-024-02966-5 |
| Abstrakt: |
Signaling of G protein-activated inwardly rectifying K + (GIRK) channels is an important mechanism of the parasympathetic regulation of the heart rate and cardiac excitability. GIRK channels are inhibited during stimulation of G q -coupled receptors (G q PCRs) by depletion of phosphatidyl-4,5-bisphosphate (PIP 2 ) and/or channel phosphorylation by protein kinase C (PKC). The G q PCR-dependent modulation of GIRK currents in terms of specific PKC isoform activation was analyzed in voltage-clamp experiments in rat atrial myocytes and in CHO or HEK 293 cells. By using specific PKC inhibitors, we identified the receptor-activated PKC isoforms that contribute to phenylephrine- and angiotensin-induced GIRK channel inhibition. We demonstrate that the cPKC isoform PKCα significantly contributes to GIRK inhibition during stimulation of wildtype α 1B -adrenergic receptors (α 1B -ARs). Deletion of the α 1B -AR serine residues S 396 and S 400 results in a preferential regulation of GIRK activity by PKCβ. As a novel finding, we report that the AT 1 -receptor-induced GIRK inhibition depends on the activation of the nPKC isoform PKCε whereas PKCα and PKCβ do not mainly participate in the angiotensin-mediated GIRK reduction. Expression of the dominant negative (DN) PKCε prolonged the onset of GIRK inhibition and significantly reduced AT 1 -R desensitization, indicating that PKCε regulates both GIRK channel activity and the strength of the receptor signal via a negative feedback mechanism. The serine residue S 418 represents an important phosphorylation site for PKCε in the GIRK4 subunit. To analyze the functional impact of this PKC phosphorylation site for receptor-specific GIRK channel modulation, we monitored the activity of a phosphorylation-deficient (GIRK4 (S418A)) GIRK4 channel mutant during stimulation of α 1B -ARs or AT 1 -receptors. Mutation of S 418 did not impede α 1B -AR-mediated GIRK inhibition, suggesting that S 418 within the GIRK4 subunit is not subject to PKCα-induced phosphorylation. Furthermore, activation of angiotensin receptors induced pronounced GIRK4 (S418A) channel inhibition, excluding that this phosphorylation site contributes to the AT 1 -R-induced GIRK reduction. Instead, phosphorylation of S 418 has a facilitative effect on GIRK activity that was abolished in the GIRK4 (S418A) mutant. To summarize, the present study shows that the receptor-dependent regulation of atrial GIRK channels is attributed to the G q PCR-specific activation of different PKC isoforms. Receptor-specific activated PKC isoforms target distinct phosphorylation sites within the GIRK4 subunit, resulting in differential regulation of GIRK channel activity with either facilitative or inhibitory effects on GIRK currents.
(© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.) |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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