title: The Arabidopsis R-SNARE VAMP721 Interacts with KAT1 and KC1 K+ Channels to Moderate K+ Current at the Plasma Membrane.
abstract: SNARE (soluble N-ethylmaleimide-sensitive factor protein attachment protein receptor) proteins drive vesicle traffic, delivering membrane and cargo to target sites within the cell and at its surface. They contribute to cell homeostasis, morphogenesis, and pathogen defense. A subset of SNAREs, including the Arabidopsis thaliana SNARE SYP121, are known also to coordinate solute uptake via physical interactions with K(+) channels and to moderate their gating at the plasma membrane. Here, we identify a second subset of SNAREs that interact to control these K(+) channels, but with opposing actions on gating. We show that VAMPs (vesicle-associated membrane proteins), which target vesicles to the plasma membrane, also interact with and suppress the activities of the inward-rectifying K(+) channels KAT1 and KC1. Interactions were evident in yeast split-ubiquitin assays, they were recovered in vivo by ratiometric bimolecular fluorescence complementation, and they were sensitive to mutation of a single residue, Tyr-57, within the longin domain of VAMP721. Interaction was also recovered on exchange of the residue at this site in the homolog VAMP723, which normally localizes to the endoplasmic reticulum and otherwise did not interact. Functional analysis showed reduced channel activity and alterations in voltage sensitivity that are best explained by a physical interaction with the channel gates. These actions complement those of SYP121, a cognate SNARE partner of VAMP721, and lead us to propose that the channel interactions reflect a "hand-off" in channel control between the two SNARE proteins that is woven together with vesicle fusion.
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
authors.forename: Ben
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
authors.forename: Rucha
authors.initials: R
authors.lastname: Karnik
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
authors.forename: Yizhou
authors.initials: Y
authors.lastname: Wang
authors.affiliation: ZMBP Developmental Genetics, D-72076 Tuebingen, Germany.
authors.forename: Niklas
authors.initials: N
authors.lastname: Wallmeroth
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom michael.blatt@glasgow.ac.uk.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Blatt
authors.affiliation: ZMBP Developmental Genetics, D-72076 Tuebingen, Germany.
authors.forename: Christopher
authors.initials: C
authors.lastname: Grefen
mesh_terms: D017360:Arabidopsis / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying / Q000502:physiology*; D050683:R-SNARE Proteins / Q000502:physiology*; D027981:Symporters / Q000502:physiology*; D000096922:K Cl- Cotransporters
chemical_list: D029681:Arabidopsis Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D050683:R-SNARE Proteins; D027981:Symporters; D000096922:K Cl- Cotransporters; C501210:KAT1 protein, Arabidopsis; C570049:VAMP721 protein, Arabidopsis