Characterization of the Protein Tyrosine Phosphatase LmPRL-1 Secreted by Leishmania major via the Exosome Pathway

Abstract

Similar to other intracellular pathogens, Leishmania parasites are known to evade the antimicrobial effector functions of host immune cells. To date, however, only a few virulence factors have been described for Leishmania major, one of the causative agents of cutaneous leishmaniasis. Here, we have characterized the expression and function of an L. major phosphatase, which we termed LmPRL-1. This enzyme shows a strong structural similarity to the human phosphatases of regenerating liver (PRL-1, -2, and -3) that regulate the proliferation, differentiation, and motility of cells. The biochemical characterization of the L. major phosphatase revealed that the enzyme is redox sensitive. When analyzing the subcellular localization of LmPRL-1 in promastigotes, amastigotes, and infected macrophages, we found that the phosphatase was predominantly expressed and secreted by promastigotes via the exosome route. Finally, we observed that ectopic expression of LmPRL-1 in L. major led to an increased number of parasites in macrophages. From these data, we conclude that the L. major phosphatase LmPRL-1 contributes to the intracellular survival of the parasites in macrophages.KEYWORDS Leishmania, exosome, macrophage, tyrosine phosphatase L eishmaniasis is an infectious disease prevalent worldwide that is caused by kinetoplastid protozoan parasites belonging to the genus Leishmania (1). In nature, this heteroxenous parasite is transmitted by the bites of sand flies. Following the inoculation of flagellated promastigotes into the dermis of the host, the parasites are rapidly endocytosed by phagocytic cells, in which they differentiate into amastigotes, multiply, and reach inner compartments and organs, such as draining lymph nodes, spleen, liver, and bone marrow. The life cycle of the parasite is completed after ingestion of amastigote-infected cells by sand flies during their blood meal. In the digestive tract of their vector, parasites transform back into extracellular promastigotes that develop into infectious metacyclics (2). Depending on the status of the host immune system and the Leishmania species, the infection of mammals leads either to mostly self-healing skin lesions (cutaneous leishmaniasis [CL]) or to a systemic disease, termed visceral leishmaniasis (VL) or kala-azar, that is lethal if untreated (3-5).To survive in their hosts, Leishmania parasites need to quickly adapt their growth, metabolism, and mechanisms of protection to their new environment. Interestingly, only a few genes are differentially expressed during this adaptive process, suggesting an important role for the regulation of protein translation (6). Leishmania speciesspecific gene diversity also participates in the adaptation of the parasite to its organ-

Function of Macrophage and Parasite Phosphatases in Leishmaniasis

“…Recently, our laboratory has characterized a new dual specificity phosphatase, LmPRL-1, secreted by L. major during macrophage infection ( 118 ). The LmPRL-1 gene, LmjF.16.0230 , is organized in tandem with a paralogous gene, LmjF.16.0250 , which codes for LmPRL-2.…”

“…Strikingly, during the first days of macrophage infection LmPRL-1 reached the cytoplasm of its host cells through the exosome route. There, LmPRL-1 appeared to support the intracellular replication of the parasite in primary mouse macrophages ( 118 ). We currently do not know the molecular mechanism by which LmPRL-1 promotes L. major virulence.…”

LmxM.22.0250-Encoded Dual Specificity Protein/Lipid Phosphatase Impairs Leishmania mexicana Virulence In Vitro

“…Recently, protein tyrosine phosphatases have been implicated in Leishmania pathogenesis [38,39]. In this work, we identified and characterized a novel putative virulence factor of Leishmania infection.…”

Message in a vesicle – trans-kingdom intercommunication at the vector–host interface

“…Unlike what is seen with other intracellular pathogens, infection with Leishmania parasites alone does not increase extracellular vesicle secretion (Cronemberger-Andrade et al, 2014). Leishmania promastigote exosomes carry heat-shock proteins and virulence factors, including the metalloprotease GP63 and the protein tyrosine phosphatase L. major (Lm)-PRL-1, which contribute to parasite survival in the mammalian host (Leitherer et al, 2017;Silverman et al, 2010a). Leishmania exosomes isolated from amastigotes contain siRNAs and tRNAderived small RNAs (Lambertz et al, 2015).…”