9.B.409. The Babesia bovis 10 TMS Secreted Multigene Membrane Protein (Bb-Mtm) Family
Babesia bovis causes a pathogenic form of babesiosis in cattle. Following invasion of red blood cells (RBCs) the parasite extensively modifies host cell structural and mechanical properties via the export of numerous proteins. Despite their crucial role in virulence and pathogenesis, such proteins have not been functionally characterized. Hakimi et al. 2020 described the surface biotinylation of infected RBCs (iRBCs), followed by proteomic analysis. They identified a multigene family (mtm) that encodes predicted multi-transmembrane integral membrane proteins which are exported and expressed on the surface of iRBCs. One mtm gene was downregulated in blasticidin-S-resistant parasites, suggesting an association with blasticidin S uptake. These homologues are of varying sizes with many having 10 TMSs, but some having 12, and others 16 TMSs. Repeat seœuences in the TM domain have been identified in several of these proteins.
Induced knockdown of a novel exported protein encoded by BBOV_III004280, named VESA export-associated protein (BbVEAP) with a single N-terminal TMS, resulted in a decreased growth rate, reduced RBC surface ridge numbers, mis-localized VESA1, and abrogated cytoadhesion to endothelial cells, suggesting that BbVEAP is a novel virulence factor for B. bovis (Hakimi et al. 2020).