title: Selective interaction of syntaxin 1A with KCNQ2: possible implications for specific modulation of presynaptic activity.
abstract: KCNQ2/KCNQ3 channels are the molecular correlates of the neuronal M-channels, which play a major role in the control of neuronal excitability. Notably, they differ from homomeric KCNQ2 channels in their distribution pattern within neurons, with unique expression of KCNQ2 in axons and nerve terminals. Here, combined reciprocal coimmunoprecipitation and two-electrode voltage clamp analyses in Xenopus oocytes revealed a strong association of syntaxin 1A, a major component of the exocytotic SNARE complex, with KCNQ2 homomeric channels resulting in a approximately 2-fold reduction in macroscopic conductance and approximately 2-fold slower activation kinetics. Remarkably, the interaction of KCNQ2/Q3 heteromeric channels with syntaxin 1A was significantly weaker and KCNQ3 homomeric channels were practically resistant to syntaxin 1A. Analysis of different KCNQ2 and KCNQ3 chimeras and deletion mutants combined with in-vitro binding analysis pinpointed a crucial C-terminal syntaxin 1A-association domain in KCNQ2. Pull-down and coimmunoprecipitation analyses in hippocampal and cortical synaptosomes demonstrated a physical interaction of brain KCNQ2 with syntaxin 1A, and confocal immunofluorescence microscopy showed high colocalization of KCNQ2 and syntaxin 1A at presynaptic varicosities. The selective interaction of syntaxin 1A with KCNQ2, combined with a numerical simulation of syntaxin 1A's impact in a firing-neuron model, suggest that syntaxin 1A's interaction is targeted at regulating KCNQ2 channels to fine-tune presynaptic transmitter release, without interfering with the function of KCNQ2/3 channels in neuronal firing frequency adaptation.
authors.affiliation: Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, Ramat-Aviv, Israel.
authors.forename: Noa
authors.initials: N
authors.lastname: Regev
authors.forename: Nurit
authors.initials: N
authors.lastname: Degani-Katzav
authors.forename: Alon
authors.initials: A
authors.lastname: Korngreen
authors.forename: Adi
authors.initials: A
authors.lastname: Etzioni
authors.forename: Sivan
authors.initials: S
authors.lastname: Siloni
authors.forename: Alessandro
authors.initials: A
authors.lastname: Alaimo
authors.forename: Dodo
authors.initials: D
authors.lastname: Chikvashvili
authors.forename: Alvaro
authors.initials: A
authors.lastname: Villarroel
authors.forename: Bernard
authors.initials: B
authors.lastname: Attali
authors.forename: Ilana
authors.initials: I
authors.lastname: Lotan
mesh_terms: D000818:Animals; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D007150:Immunohistochemistry; D051658:KCNQ2 Potassium Channel / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D017729:Presynaptic Terminals; D011485:Protein Binding; D050827:Syntaxin 1 / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D051658:KCNQ2 Potassium Channel; D050827:Syntaxin 1
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