Emmy Noether Project: R-SNARE K-channel interactions in coordinating vesicle trafficking and ion transport

01.05.2018 bis 30.04.2019

Vesicle trafficking is enabled by a complex interplay of protein-protein interactions. Key players are
the so-called SNARE proteins facilitating the actual membrane fusion through a tight interaction of
their intrinsic SNARE motifs that helps to overcome the strong dehydration forces associated with
lipid bilayers. Both membrane and vesicle feature a specific subset of SNAREs: Q- and RSNAREs.
Until recently, understanding of SNARE function centred on their canonical role in
vesicle fusion. A novel interaction of the Q-SNARE SYP121 with the K-channel subunit KC1 in
Arabidopsis thaliana challenged our view of SNAREs being solely involved in facilitating membrane
fusions. Under K-limiting conditions, loss-of-function lines of SYP121 phenocopy the reduced
growth of corresponding K-channel knockouts. Complementary, root impalements of syp121 lines
show loss of inward K-currents suggesting a regulatory role on channel activity, probably through
direct modulation of its gating behaviour. Interestingly, the mechanism of the interaction is
executed through a novel motif at the N-terminus of the SNARE. This motif lies beyond previously
identified SNARE domains which are implicated in core complex formation. These findings allow
new hypotheses on additional, non-canonical roles of SNARE proteins.
This proposal is based on our recent discovery that specific members of the R-SNARE family
interact with K-channels as well. Research on R-SNAREs at present mainly focusses on their role in vesicle trafficking and is largely based on findings in the animal field. In plants, pathogen
resistance and cytokinesis are dependent on R-SNAREs canonical function in directing and driving
vesicle-trafficking. A functional role of the interaction of an R-SNARE with K-channels will allow an
alternative approach for understanding SNARE function in general and its involvement in Kchannel
regulation in particular. Questions that will be addressed within the scope of this project
should 1.) lead to a detailed understanding of the molecular mechanism of the interaction, 2.)
resolve trafficking-related effects in connection with the SNARE-channel interaction and 3.) explain
functional consequences in plant growth and development. Dissecting the involvement of different
types of SNAREs in K-channel interaction is likely to yield a mechanistic view involving either
competition of the SNAREs or sequential binding. Elucidating the mechanism of SNARE-channel
interaction as a dynamic process linking vesicle trafficking with ion transport is expected to lead to
a paradigm shift for SNARE function in general.