SNAP23 Regulates KCC2 Membrane Insertion and Activity Following mZnR/GPR39 Activation in Hippocampal Neurons

Abstract

Modulation of neuronal K+/Cl- cotransporter 2 (KCC2) activity, which mediates Cl- export, is considered to be regulated by phosphorylation of its C-terminus and critical to neuronal function. Here, we show that KCC2 interacts with the SNARE protein Synaptosome Associated Protein 23, SNAP23, an essential component of membrane insertion machinery. Using KCC2 truncated mutants, we show that KCC2 C-terminal domain is essential for the Zn2+-sensitive receptor mZnR/GPR39 upregulation of KCC2 activity and membrane targeting in HEK293 cells. Surprisingly, we found that SNAP23 is essential for ZnR/GPR39-dependent upregulation of transport mediated by KCC2 and its epithelial isoform KCC3. Moreover, IκB kinase (IKK)-dependent phosphorylation of SNAP23 is essential for ZnR/GPR39 upregulation of KCC2 activity in mouse hippocampal neurons. Finally, we found that interaction of SNAP23 and Syntaxin 1A with KCC2 enhances its insertion into the neuronal membrane. Our results elucidate a G-protein coupled receptor dependent pathway for regulation of KCC activity that via interaction with SNARE proteins.