GRASP negatively regulates the secretion of the virulence factor gp63 in Leishmania.

ABSTRACT

Metalloprotease-gp63 is a virulence factor secreted by Leishmania. However, secretory pathway in Leishmania is not well defined. Here, we cloned and expressed the GRASP homolog from Leishmania. We found that Leishmania expresses one GRASP homolog of 58 kDa protein (LdGRASP) which localizes in LdRab1- and LPG2-positive Golgi compartment in Leishmania. LdGRASP was found to bind with COPII complex, LdARF1, LdRab1 and LdRab11 indicating its role in ER and Golgi transport in Leishmania. To determine the function of LdGRASP, we generated LdGRASP knockout parasites using CRISPR-Cas9. We found fragmentation of Golgi in LdGRASPKO parasites. Our results showed enhanced transport of non-GPI-anchored gp63 to the cell surface leading to higher secretion of this form of gp63 in LdGRASPKO parasites in comparison to LdWT cells. In contrast, we found that transport of GPI-anchored gp63 to the cell surface is blocked in LdGRASPKO parasites and thereby inhibits its secretion. The overexpression of dominant-negative mutant of LdRab1 or LdSar1 in LdGRASPKO parasites significantly blocked the secretion of non-GPI-anchored gp63. Interestingly, we found that survival of transgenic parasites overexpressing LdGRASP-GFP is significantly compromised in macrophages in comparison to LdWT and LdGRASPKO parasites. These results demonstrated that LdGRASP differentially regulates Ldgp63 secretory pathway in Leishmania.