K+ Channel-SEC11 Binding Exchange Regulates SNARE Assembly for Secretory Traffic.

Sakharam Waghmare,Naomi Donald,Michael R. Blatt,Ben Zhang,Edita Liliekyte,Cecile Lefoulon

doi:10.1104/pp.19.00919

Abstract

Cell expansion requires that ion transport and secretory membrane traffic operate in concert. Evidence from Arabidopsis (Arabidopsis thaliana) indicates that such coordination is mediated by physical interactions between subsets of so-called SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, which drive the final stages of vesicle fusion, and K+ channels, which facilitate uptake of the cation to maintain cell turgor pressure as the cell expands. However, the sequence of SNARE binding with the K+ channels and its interweaving within the events of SNARE complex assembly for exocytosis remains unclear. We have combined protein-protein interaction and electrophysiological analyses to resolve the binding interactions of the hetero-oligomeric associations. We find that the RYxxWE motif, located within the voltage sensor of the K+ channels, is a nexus for multiple SNARE interactions. Of these, K+ channel binding and its displacement of the regulatory protein SEC11 is critical to prime the Qa-SNARE SYP121. Our results indicate a stabilizing role for the Qbc-SNARE SNAP33 in the Qa-SNARE transition to SNARE complex assembly with the R-SNARE VAMP721. They also suggest that, on its own, the R-SNARE enters an anomalous binding mode with the channels, possibly as a fail-safe measure to ensure a correct binding sequence. Thus, we suggest that SYP121 binding to the K+ channels serves the role of a primary trigger to initiate assembly of the secretory machinery for exocytosis.

Highlights

Introduction(Arabidopsis thaliana) indicates that such coordination is mediated by physical interactions between subsets of so-called SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, which drive the final stages of vesicle fusion, and K1 channels, which facilitate uptake of the cation to maintain cell turgor pressure as the cell expands
(Arabidopsis thaliana) indicates that such coordination is mediated by physical interactions between subsets of so-called SNARE proteins, which drive the final stages of vesicle fusion, and K1 channels, which facilitate uptake of the cation to maintain cell turgor pressure as the cell expands
We find that all three cognate SNAREs, SYP121, VAMP721, and SNAP33, bind with the N-terminal cytosolic domain of the K1 channels KAT1 and KC1 through the conserved linear motif RYxxWE situated at the cytosolic base of the first transmembrane a-helix of the channel voltage sensor domain (VSD)

Summary

Introduction

(Arabidopsis thaliana) indicates that such coordination is mediated by physical interactions between subsets of so-called SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, which drive the final stages of vesicle fusion, and K1 channels, which facilitate uptake of the cation to maintain cell turgor pressure as the cell expands. SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins have important roles in membrane traffic. In plants, they contribute to cell homeostasis and responses to biotic and abiotic stress, and they are vital for development and morphogenesis (Shope and Mott, 2006; Campanoni and Blatt, 2007; Kwon et al, 2008; Eisenach et al, 2012). K+ Channel Binding in SNARE Assembly to SNARE complex assembly (Burgoyne and Morgan, 2007; Ma et al, 2013; Demircioglu et al, 2014)

Methods

Results

Conclusion