Metalloprotease Gp63 targeting novel glycoside exhibits potential antileishmanial activity

Abstract

Visceral Leishmaniasis (VL) and its aggressive cutaneous exacerbation known as Post Kala-azar Dermal Leishmaniasis (PKDL) cause a huge disease burden in tropics and sub-tropic endemic zones worldwide. Contemporary treatment modalities have been associated with various complications. Encouraged from the recent marked antimalarial effects from plant derived glycosides; here we have chemically synthesized a library of diverse Glycoside derivatives (Gly 1-12) and evaluated their inhibitory efficacy against Ag83 strain of Leishmania donovani. In vitro activity of Glycoside-2 (Gly 2) on Ag83 strain, unravelled its prominent anti-leishmanial property with IC50 value of 1.13μM. In-silico studies also unveiled the efficacy of Gly 2 to bind to the membrane surface of parasite. The toxic effect of Gly 2 causes necrosis like death in promastigote by abrogating its proliferation leading to imbalanced redox homeostasis by disruption of mitochondrial membrane potential. Additionally, Gly 2 treatment demonstrated increased susceptibility of parasites towards complement mediated lysis and displayed strong lethal effect on amastigote-macrophage infection model mimicking pathophysiological condition of body. This lead molecule was quite effective against the clinical PKDL strain BS12 with IC50 value of 1.97 μM making it the most suitable drug so far which can target both VL and PKDL simultaneously. Based on the above experimental validations we narrowed our thoughts regarding the potent role of Gly 2 targeting surface protein of L. donovani such as Gp63, a zinc metalloprotease. Further analysis of structure activity relationship (SAR) of these glycoside derivatives, demonstrated exceptional binding affinity of Gly 2 towards Gp63, a zinc metalloprotease of L. donovani; with strong H-bond interactions of Gly 2 with catalytic domain in the α-helix B region of Gp63. The strong confined interactions between Gly 2 and the target protein Gp63 in a physiologically relevant cellular environment was further assessed by Cellular Thermal Shift Assay (CETSA) which corroborated with our previous results. Taken together, this study reports the serendipitous discovery of glycoside derivative Gly 2 with enhanced leishmanicidal activity and proves to be novel chemotherapeutic prototype against VL and PKDL.

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“…2 The multifunctional virulence factor Glycoprotein 63 (GP63) has been characterized as being abundant on the surface of Leishmania spp. 3 It is the main enzyme in parasite replication, promastigote binding to and internalization in macrophages, and attenuation of reactive oxygen species formation (ROS), which favors amastigote proliferation. 3 , 4 This gene with higher copy numbers encodes a surface protein, and is an essential virulence factor in Leishmani a, favoring rapid migration, internalization, and survival in host macrophages.…”