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alpha1-adrenoceptors regulate only the caveolae-located subpopulation of cardiac K(V)4 channels.

Authors: Alday, A  Urrutia, J  Gallego, M  Casis, O 
Citation: Alday A, etal., Channels (Austin). 2010 May-Jun;4(3):168-78.
Pubmed: (View Article at PubMed) PMID:20224290

In ventricular myocytes, alpha1-AR stimulates Galphas proteins and reduces the transient outward K(+) current (I(to)) via a cAMP/PKA-mediated pathway and thus regulates cardiac contraction and excitability. This I(to) reduction is compartmentalized and limited to discrete membrane regions since PKA-dependent phosphorylation of the I(to) channels after alpha1-AR stimulation requires the integrity of both the sarcoplasmic membrane and the cytoskeleton. The aim of this work was to investigate the mechanisms involved in the compartmentalization of the PKA-dependent modulation of I(to) in response to alpha1-AR activation. I(to) current recordings were performed by the Patch-Clamp technique. Membrane rafts from isolated ventricular myocytes were extracted by centrifugation in a sucrose density gradient. The different proteins were visualized by western blot and protein-protein interactions determined by coimmunoprecipitation experiments. Localization of I(to) channel in caveolae, particular subtypes of membrane rafts, was achieved by electron microscopy. Patch-Clamp recordings show that a functional supramolecular complex, kept together by the Akinase anchoring protein AKAP100, exist in caveolae in living myocytes. Density gradients and immunoprecipitation experiments show that the components of the alpha1-AR/I(to) pathway localize in caveolae, forming two different groups of proteins. The K(V)4.2/K(V)4.3 channel forms a supramolecular complex with PKA through AKAP100 and is attached to caveolae by interacting with caveolin-3. On the other hand, alpha1-AR, Galphas and adenylate cyclase gather in a second group also connected to caveolin-3. Therefore, both groups of preassembled proteins are maintained in close proximity by caveolin-3. A different I(to) channel population localizes in non-caveolar membrane rafts and is not sensitive to alpha1-adrenergic regulation.

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CRRD Object Information
CRRD ID: 6902941
Created: 2012-09-25
Species: All species
Last Modified: 2012-09-25
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.