Leishmania major targets macrophage Syntaxin-2 to impair phagolysosome biogenesis and promote intracellular survival

Abstract

Macrophages destroy pathogens by engulfing them into phagosomes that mature into degradative phagolysosomes via lysosome fusion. Leishmania parasites subvert this antimicrobial pathway to establish intracellular infection and cause leishmaniasis. We previously identified the SNARE protein syntaxin-2 (Stx2) as a promoter of phagolysosome biogenesis that simultaneously limits particle binding and uptake. Consistent with this dual role, Stx2-depleted macrophages (Stx2-KD) show enhanced binding and internalization of Leishmania major. Stx2-KD macrophages also sustain higher intracellular parasite loads. We find that L. major actively targets macrophage Stx2 by selectively depleting Stx2 from phagosomes through its virulence metalloprotease GP63. Phagosomes containing GP63-deficient L. major retain Stx2 and acquire increased levels of lysosomal hydrolases and v-ATPase, restoring degradative capacity. In BALB/c mice, L. major infection markedly reduces Stx2 in infected tissues in a GP63-dependent manner. Collectively, our findings identify GP63-mediated Stx2 depletion as a key virulence strategy of L. major, positioning the GP63-Stx2 axis as a promising therapeutic target for leishmaniasis.