A-kinase anchoring protein 79/150 facilitates the phosphorylation of GABAA receptors by cAMP-dependent protein kinase via selective interaction with receptor β subunits

MRC Laboratory for Molecular Cell Biology and Department of Pharmacology, University College London, Gower Street, London WCIE 6BT, UK; Howard Hughes Medical Institute, Vollum Institute, Oregon Health Sciences University, Portland, OR 97201, USA
Molecular and Cellular Neuroscience (Impact Factor: 3.73). 01/2003; DOI: 10.1016/S1044-7431(02)00017-9

ABSTRACT GABAA receptors, the key mediators of fast synaptic inhibition in the brain, are predominantly constructed from α(1–6), β(1–3), γ(1–3), and δ subunit classes. Phosphorylation by cAMP-dependent protein kinase (PKA) differentially regulates receptor function dependent upon β subunit identity, but how this kinase is selectively targeted to GABAA receptor subtypes remains unresolved. Here we establish that the A-kinase anchoring protein 150 (AKAP150), directly binds to the receptor β1 and β3, but not to α1, α2, α3, α6, β2, γ2, or δ subunits. Furthermore, AKAP79/150 is critical for PKA-mediated phosphorylation of the receptor β3 subunit. Together, our observations suggest a mechanism for the selective targeting of PKA to GABAA receptor subtypes containing the β1 or β3 subunits dependent upon AKAP150. Therefore, the selective interaction of β subunits with AKAP150 may facilitate GABAA receptor subtype-specific functional modulation by PKA activity which may have profound local effects on neuronal excitation.

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    ABSTRACT: Ethanol causes pathological changes in GABAA receptor trafficking and function. These changes are mediated in part by ethanol activation of protein kinase A (PKA). The current study investigated the expression of the GABAA α1 and α4 subunits and the kinase anchoring protein AKAP150, as well as bicuculline-induced seizure threshold, at baseline and following acute injection of ethanol (3.5 g/kg IP) in a mouse line lacking the regulatory RIIβ subunit of PKA. Whole cerebral cortices were harvested at baseline, 1 h, or 46 h following injection of ethanol or saline and subjected to fractionation and western blot analysis. Knockout (RIIβ-/-) mice had similar baseline levels of PKA RIIα and GABAA α1 and α4 subunits compared to wild type (RIIβ+/+) littermates, but had deficits in AKAP150. GABAA α1 subunit levels were decreased in the P2 fraction of RIIβ-/-, but not RIIβ+/+, mice following 1 h ethanol, an effect that was driven by decreased α1 expression in the synaptic fraction. GABAA α4 subunits in the P2 fraction were not affected by 1 h ethanol; however, synaptic α4 subunit expression was increased in RIIβ+/+, but not RIIβ-/- mice, while extrasynaptic α4 and δ subunit expression were decreased in RIIβ-/-, but not RIIβ+/+ mice. Finally, RIIβ knockout was protective against bicuculline-induced seizure susceptibility. Overall, the results suggest that PKA has differential roles in regulating GABAA receptor subunits. PKA may protect against ethanol-induced deficits in synaptic α1 and extrasynaptic α4 receptors, but may facilitate the increase of synaptic α4 receptors.
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