The human VAMP7 isoforms: preliminary characterization and their role in neuritogenesis

VAMP7 (Vesicular Associated Membrane Protein 7) is a SNARE protein of the longin family conserved among eukaryotes. It plays a significant role in several physiological human processes, including neuritogenesis. Human VAMP7 gene (SYBL1) undergoes alternative splicing, thus leading to seven different isoforms: the main isoform VAMP7a, the non-SNARE variants VAMP7b, VAMP7i, VAMP7j and the non-longin variants VAMP7d, VAMP7h, VAMP7c. To better understand their function and role in L1CAM transport, this thesis analysed the specific effect of such isoforms during the neuritogenesis process and their subcellular localization. The experiments were performed in both proliferating and differentiated, neuroblastoma-derived SH-SY5Y cells. In this context, VAMP7j and VAMP7dh act respectively as a constitutive repressor and a constitutive inducer of neurite growth. Given the importance of the phosphorylation state of Y45 for VAMP7a activity, the repressor effect of VAMP7j on neuritogenesis may depend on Y45 as well. Therefore, the specific function of phosphorylation in VAMP7j was investigated by cloning a phosphomimetic and a non-phosphorylatable variant.