Entamoeba lysyl-tRNA Synthetase Contains a Cytokine-Like Domain with Chemokine Activity towards Human Endothelial Cells

Abstract

Immunological pressure encountered by protozoan parasites drives the selection of strategies to modulate or avoid the immune responses of their hosts. Here we show that the parasite Entamoeba histolytica has evolved a chemokine that mimics the sequence, structure, and function of the human cytokine HsEMAPII (Homo sapiens endothelial monocyte activating polypeptide II). This Entamoeba EMAPII-like polypeptide (EELP) is translated as a domain attached to two different aminoacyl-tRNA synthetases (aaRS) that are overexpressed when parasites are exposed to inflammatory signals. EELP is dispensable for the tRNA aminoacylation activity of the enzymes that harbor it, and it is cleaved from them by Entamoeba proteases to generate a standalone cytokine. Isolated EELP acts as a chemoattractant for human cells, but its cell specificity is different from that of HsEMAPII. We show that cell specificity differences between HsEMAPII and EELP can be swapped by site directed mutagenesis of only two residues in the cytokines' signal sequence. Thus, Entamoeba has evolved a functional mimic of an aaRS-associated human cytokine with modified cell specificity.

Crystal structures of Entamoeba histolytica lysyl‐tRNA synthetase reveal conformational changes upon lysine binding and a specific helix bundle domain

“…E. coli C41(DE3) cells were transformed with pET30-EhKRS vector [15]. The resulting recombinant protein harbors an amino-terminal hexahistidine tag and two additional residues from the cloning process (MHHHHHHML instead of the initial M).…”

“…In the genus Entamoeba , lysyl‐ and methionyl‐tRNA synthetases (EhKRS and EhMRS) share a common C‐terminal domain of 166 amino acids. This domain is highly similar to the human endothelial monocyte activating polypeptide II (EMAPII), and was named Entamoeba EMAPII‐like polypeptide (EELP) [15]. Human EMAPII is an inflammatory cytokine that induces apoptosis and migration in endothelial cells [16].…”

“…In Entamoeba , EELP is proteolytically released from the EhKRS and localized at the surface of the parasite. This polypeptide was proposed to facilitate the escape of Entamoeba from the host immune system, through modulation of the host cellular environment [15].…”

“…In Entamoeba, EELP is proteolytically released from the EhKRS and localized at the surface of the parasite. This polypeptide was proposed to facilitate the escape of Entamoeba from the host immune system, through modulation of the host cellular environment [15]. Class II KRS crystal structures have been solved in bacteria and eukaryotes: namely Escherichia coli [17][18][19], Thermus thermophilus [20], Geobacillus stearothermophilus [21], Burkholderia thailandensis [22], Plasmodium falciparum [23,24] and Homo sapiens [25,26].…”

Twin Attributes of Tyrosyl-tRNA Synthetase of Leishmania donovani

“…Studies have indicated that human tyrosyl-, tryptophanyl-, and lysyl-tRNA synthetases can be secreted extracellularly and can mimic cytokines (4,31,32). TyrRS of Plasmodium and LysRS of Entamoeba also mimic the functions of human cytokines (24,33).…”