Dopaminergic modulation of voltage-gated Na+ current in rat hippocampal neurons requires anchoring of cAMP-dependent protein kinase

Activation of D1-like dopamine (DA) receptors reduces peak Na+ current in a cutely isolated hippocampal neurons via a modulatory mechanism involving ph osphorylation of the Na+ channel a subunit by cAMP-dependent protein kinase (PKA). Peak Na+ current is reduced 20-50% in the presence of the D1 agonis t SKF 81297 or the PKA activator Sp-5,6-dichloro-l-beta-D-ribofuranosyl ben zimidazole-3',5'-cyclic monophosphorothionate (cBIMPS). Co-immunoprecipitat ion experiments show that Na+ channels are associated with PKA and A-kinase -anchoring protein 15 (AKAP-15), and immunocytochemical labeling reveals th eir co-localization in the cell bodies and proximal dendrites of hippocampa l pyramidal neurons. Anchoring of PKA near the channel by an AKAP, which bi nds the RII alpha regulatory subunit, is necessary for Na+ channel modulati on in acutely dissociated hippocampal pyramidal neurons. Intracellular dial ysis with the anchoring inhibitor peptides Ht31 from a human thyroid AKAP a nd AP2 from AKAP-15 eliminated the modulation of the Na+ channel by the D1- agonist SKF 81297 and the PKA activator cBIMPS. In contrast, dialysis with the inactive proline-substituted control peptides Ht31-P and AP2-P had litt le effect on the D1 and PKA modulation. Therefore, we conclude that modulat ion of the Na+ channel by activation of D1-like DA receptors requires targe ted localization of PKA near the channel to achieve phosphorylation of the alpha subunit and to modify the functional properties of the channel.