Metalloprotease Gp63 targeting novel glycoside exhibits potential antileishmanial activity
Authors: Chakrabarti Amrita , Narayana Chintam , Joshi Nishant , Garg Swati , Garg Lalit , Sagar Ram , Pati Soumya , Singh Shailja 
Published: September 2020

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 againstAg83strain ofLeishmania donovani. In vitroactivity of Glycoside-2(Gly 2)on promastigote form ofAg83strain, unravelled its prominent anti-leishmanial property withIC50value of 1.13μM.In-silicostudies also unveiled the efficacy ofGly 2to bind to the membrane surface of parasite. The toxic effect ofGly 2causes necrosis like death in promastigote by abrogating its proliferation leading to imbalanced redox homeostasis by disruption of mitochondrial membrane potential. Additionally,Gly 2treatment 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 on promastigotes form of 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 ofGly 2targeting surface protein ofL. donovanisuch as Gp63, a zinc metalloprotease. Further analysis of structure activity relationship (SAR) of these glycoside derivatives, demonstrated exceptional binding affinity ofGly 2towards Gp63, a zinc metalloprotease ofL. donovani; with strong H-bond interactions ofGly 2with catalytic domain in the α-helix B region of Gp63. The strong confined interactions betweenGly 2and 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 derivativeGly 2with enhanced leishmanicidal activity and proves to be novel chemotherapeutic prototype against VL and PKDL.

Highlights

A novel glycoside derivative (Gly 2) targets Gp63 functioning inL. donovanipromastigotes, resulting in its abrogated proliferation and severely detabilized redox homeostasis, leading to parasitic death.

Structure activity relationship (SAR) analysis revealed exceptional ligandability of Gly 2 towards Gp63 catalytic domain bothin silicoand in Cellular Thermal Shift Assay (CETSA) basedin vitroanalysis.

Gly 2 treatment exhibited increased parasite susceptibility towards complement mediated lysis and reduced macrophage infectionin vitromimicking the pathophysiological conditions.

Gly 2 showed profound antileishmanial activity against the clinical isolates of Post Kala-azar Dermal Leishmaniasis (PKDL).