DIRECT INTERACTION IN ARABIDOPSIS OF SNARE PROTEIN SYP51 WITH NON-SNARE PROTEIN NLM1

SNAREs (N-ethylmaleimide-sensitive factor adaptor protein receptors) are small polypeptides characterized by a particular domain, the SNARE motif, that can form a coiled-coil structure. Via hetero-oligomeric interactions, these proteins form highly stable protein-protein interactions, the so called SNARE-complex, that allow membrane fusion. SNAREs also interact with several proteins acting as regulators of SNARE-complex formation. Stoichiometry of these proteins reveals that they are more abundant than required for membrane traffic. Indeed their function appears to be more diversified. It was shown (1) that they may assemble to form non-fusogenic complexes acting as interfering-SNAREs or iSNARE (2) as in the case of AtSYP51 and SYP52. It was also shown that plasma membrane SNAREs can be phosphorylated as part of the signaling cascade elicited by interaction with microorganisms or hormonal stimulation and that they influence turnover of channels. In particulat Grefen and co-workers (3; 4) provided direct evidence that SYP121 is part of a scaffold of proteins associated, by direct interaction with channel KAT1, with the membrane transport of K+. In fact, few SNARE proteins are known to interact with ion channels, notably mammalian Syntaxin 1A, which binds several different Ca2+ and K+ channels in nerves. Here we show that AtSYP51 interacts directly with a non-SNARE protein, AtNLM1, probably regulating autophagocytosis processes. Aknowledgement The authors thank the contribution of the Italian project ‘Reti di Laboratori Pubblici di Ricerca per la Selezione, Caratterizzazione e Conservazione di Germoplasma 2009’. 1) De Benedictis M, Bleve G, Faraco M, Stigliano S, Grieco F, Piro G, Dalessandro G, Di Sansebastiano GP. (2013) AtSYP51/52 Functions Diverge in the Post-Golgi Traffic and Differently Affect Vacuolar Sorting, Mol. Plant 6(3): 916-930. 2) Di Sansebastiano GP. (2013) Defining new SNARE functions: the i-SNARE. Front Plant Sci. 4: 99. 3) Grefen C, Blatt MR. (2008) SNAREs--molecular governors in signalling and development. Curr Opin Plant Biol. 11(6): 600-9. 4) Grefen C, Chen Z, Honsbein A, Donald N, Hills A, Blatt MR. (2010) A novel motif essential for SNARE interaction with the K(+) channel KC1 and channel gating in Arabidopsis. Plant Cell. 22(9): 3076-92.