Phylogenetic and Structural Analyses of Vesicular Glutamate Transporters

Vesicular glutamate transporters are members of the solute carrier 17 (SLC17) family, and mammals express three closely related isoforms: vGluT1-3. While vGluT genes have been identified across various species in the Animalia kingdom, the evolutionary relationships and the natural history of vGluT members remain poorly understood. This study aimed to address these gaps by presenting a phylogenetic analysis of vGluTs across the animal kingdom. The study also included a detailed sequence analysis and structural modeling of vGluT isoforms among species. The phylogenetic tree revealed distinct clusters corresponding to the vGluts isoform 1, 2, and 3, with functional amino acid residues highly conserved among them. Invertebrate vGluTs emerged as the most divergent proteins, serving as the root of the tree. Sequence analysis confirmed the high conservation of vGluTs transmembrane core regions but identified high variations in the N and C-terminal ones. Structural analysis revealed that AlphaFold2-predicted models demonstrated high confidence quality in the transmembrane domains, but exhibited limited local similarity in the N-terminal, C-terminal, and loop regions. On the other hand, the expected topology of these helices was accurately captured and positioned in the Swiss-Model-generated structures, with the functionally relevant residues precisely positioned in three-dimensional space. In conclusion, we expect that our findings will contribute to a deeper understanding of vesicular glutamate transporter structure and function, as well as their roles across distinct species and biological contexts.