Calcineurin is required for Leishmania major stress response pathways and for virulence in the mammalian host

Thomas Naderer, Orwa Dandash, Malcolm J McConville

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Abstract

Leishmania parasites must adapt to elevated temperatures and other environmental stresses during infection of their mammalian hosts. How these environmental cues are sensed is poorly understood. In this study we show that calcium uptake is required for parasite thermotolerance at 34a??37A?C. To identify potential downstream targets of calcium influx, a Leishmania major mutant lacking the essential regulatory subunit (CnB) of the Ca2+/calmodulin-dependent serine/threonine-specific phosphatase, calcineurin, was generated. The I?cnb mutant grew as well as wild-type parasites at 27A?C and differentiated normally to infective metacyclic promastigotes. However, I?cnb parasites lost viability when exposed to increased temperature (34A?C) and were hypersensitive to endoplasmic reticulum and membrane stress, induced by tunicamycin and inhibitors of sterol and sphingolipid biosynthesis respectively. I?cnb promastigotes were internalized by macrophages, but their differentiation to the heat adapted amastigote stage was delayed and the resulting parasites failed to proliferate. Strikingly, the I?cnb parasites were completely cleared by susceptible BALB/c mice. Complementation of I?cnb parasites with CnB restored thermotolerance and infectivity in both macrophages and animal models. Our results suggest that Ca2+ influx and calcineurin signalling are required for both early and long-term adaptive parasite responses to environmental stresses encountered in the mammalian host.
Original languageEnglish
Pages (from-to)471 - 480
Number of pages10
JournalMolecular Microbiology
Volume80
Issue number2
DOIs
Publication statusPublished - 2011
Externally publishedYes

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