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Sensing Host Arginine Is Essential for Leishmania Parasites' Intracellular Development.

mBio (2020-10-15)
Adele Goldman-Pinkovich, Sriram Kannan, Roni Nitzan-Koren, Madhu Puri, Harsh Pawar, Yael Bar-Avraham, Jacquelyn McDonald, Aakash Sur, Wen-Wei Zhang, Greg Matlashewski, Rentala Madhubala, Shulamit Michaeli, Peter J Myler, Dan Zilberstein
ABSTRACT

Arginine homeostasis in lysosomes is critical for the growth and metabolism of mammalian cells. Phagolysosomes of macrophages are the niche where the parasitic protozoan Leishmania resides and causes human leishmaniasis. During infection, parasites encounter arginine deprivation, which is monitored by a sensor on the parasite cell surface. The sensor promptly activates a mitogen-activated protein kinase 2 (MAPK2)-mediated arginine deprivation response (ADR) pathway, resulting in upregulating the abundance and activity of the Leishmania arginine transporter (AAP3). Significantly, the ADR is also activated during macrophage infection, implying that arginine levels within the host phagolysosome are limiting for growth. We hypothesize that ADR-mediated upregulation of AAP3 activity is necessary to withstand arginine starvation, suggesting that the ADR is essential for parasite intracellular development. CRISPR/Cas9-mediated disruption of the AAP3 locus yielded mutants that retain a basal level of arginine transport but lack the ability to respond to arginine starvation. While these mutants grow normally in culture, they were impaired in their ability to develop inside THP-1 macrophages and were ∼70 to 80% less infective in BALB/c mice. Hence, inside the host macrophage, Leishmania must overcome the arginine "hunger games" by upregulating the transport of arginine via the ADR. We show that the ability to monitor and respond to changes in host metabolite levels is essential for pathogenesis.IMPORTANCE In this study, we report that the ability of the human pathogen Leishmania to sense and monitor the lack of arginine in the phagolysosome of the host macrophage is essential for disease development. Phagolysosomes of macrophages are the niche where Leishmania resides and causes human leishmaniasis. During infection, the arginine concentration in the phagolysosome decreases as part of the host innate immune response. An arginine sensor on the Leishmania cell surface activates an arginine deprivation response pathway that upregulates the expression of a parasite arginine transporter (AAP3). Here, we use CRISPR/Cas9-mediated disruption of the AAP3 locus to show that this response enables Leishmania parasites to successfully compete with the host macrophage in the "hunger games" for arginine.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
RPMI-1640 Medium, With L-glutamine and sodium bicarbonate, liquid, sterile-filtered, suitable for cell culture
Sigma-Aldrich
TRI Reagent®, For processing tissues, cells cultured in monolayer or cell pellets
Sigma-Aldrich
Phorbol 12-myristate 13-acetate, ≥99% (TLC), film or powder
Sigma-Aldrich
Giemsa Stain, Modified Solution, according to Giemsa
SAFC
RPMI-1640 Medium, With L-glutamine and sodium bicarbonate. Without arginine, leucine, lysine, and phenol red, liquid, sterile-filtered, suitable for cell culture, designed for isotope labeling for cell culture applications