mGlu4 potentiation of K2P2.1 is dependant on C-terminal dephosphorylation

Two-pore domain potassium (K2P) channels are proposed to underlie the background or leak current found in many excitable cells. Extensive studies have been performed investigating the inhibition of K2P2.1 by Gαq- and Gαs-coupled G-protein-coupled receptors (GPCRs), whereas in the present study we investigate the mechanisms underlying Gαi/Gαo-coupled GPCR increases in K2P2.1 activity. Activation of mGlu4 increases K2P2.1 activity, with pharmacological inhibition of protein kinases and phosphatases revealing the involvement of PKA whereas PKC, PKG or protein phosphatases play no role. Mutational analysis of potential C-terminal phosphorylation sites indicates S333 to control approximately 70%, with S300 controlling approximately 30% of the increase in K2P2.1 activity following mGlu4 activation. These data reveal that activation of mGlu4 leads to an increase in K2P2.1 activity through a reduction in C-terminal phosphorylation, which represents a novel mechanism by which group III mGlu receptors may regulate cell excitability and synaptic activity.