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Toxoplasma DJ-1 Regulates Organelle Secretion by a Direct Interaction with Calcium-Dependent Protein Kinase 1.

ABSTRACT: Human DJ-1 is a highly conserved and yet functionally enigmatic protein associated with a heritable form of Parkinson's disease. It has been suggested to be a redox-dependent regulatory scaffold, binding to proteins to modulate their function. Here we present the X-ray crystal structure of the Toxoplasma orthologue Toxoplasma gondii DJ-1 (TgDJ-1) at 2.1-Å resolution and show that it directly associates with calcium-dependent protein kinase 1 (CDPK1). The TgDJ-1 structure identifies an orthologously conserved arginine dyad that acts as a phospho-gatekeeper motif to control complex formation. We determined that the binding of TgDJ-1 to CDPK1 is sensitive to oxidation and calcium, and that this interaction potentiates CDPK1 kinase activity. Finally, we show that genetic deletion of TgDJ-1 results in upregulation of CDPK1 expression and that disruption of the CDPK1/TgDJ-1 complex in vivo prevents normal exocytosis of parasite virulence-associated organelles called micronemes. Overall, our data suggest that TgDJ-1 functions as a noncanonical kinase-regulatory scaffold that integrates multiple intracellular signals to tune microneme exocytosis in T. gondiiIMPORTANCE Apicomplexan parasites such as Toxoplasma and Plasmodium are obligate intracellular parasites that require the protective environment of a host cell in order to replicate and survive within a host organism. These parasites secrete effector proteins from specialized apical organelles to select and invade a chosen host cell. The secretion of these organelles is a tightly regulated process coordinated by endogenous small molecules and calcium-dependent protein kinases. We previously identified the Toxoplasma orthologue of the highly conserved protein DJ-1 as a regulator of microneme secretion, but the molecular basis for this was not known. We have now identified the molecular mechanism for how TgDJ-1 regulates microneme secretion. TgDJ-1 interacts with the kinase responsible for the secretion of these organelles (calcium-dependent kinase 1) and synergizes with calcium to potentiate kinase activity. This interaction is direct, phosphodependent, and necessary for the normal secretion of these important organelles.

SUBMITTER: Child MA

PROVIDER: S-EPMC5347346 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Toxoplasma DJ-1 Regulates Organelle Secretion by a Direct Interaction with Calcium-Dependent Protein Kinase 1.

Child Matthew A MA Garland Megan M Foe Ian I Madzelan Peter P Treeck Moritz M van der Linden Wouter A WA Oresic Bender Kristina K Weerapana Eranthie E Wilson Mark A MA Boothroyd John C JC Reese Michael L ML Bogyo Matthew M

mBio 20170228 1

Human DJ-1 is a highly conserved and yet functionally enigmatic protein associated with a heritable form of Parkinson's disease. It has been suggested to be a redox-dependent regulatory scaffold, binding to proteins to modulate their function. Here we present the X-ray crystal structure of the <i>Toxoplasma</i> orthologue <i>Toxoplasma gondii</i> DJ-1 (TgDJ-1) at 2.1-Å resolution and show that it directly associates with calcium-dependent protein kinase 1 (CDPK1). The TgDJ-1 structure identifies ...[more]

PMID: 28246362

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Project description:Calcium-regulated exocytosis is a ubiquitous process in eukaryotes, whereby secretory vesicles fuse with the plasma membrane and release their contents in response to an intracellular calcium surge. This process regulates various cellular functions such as plasma membrane repair in plants and animals, the discharge of defensive spikes in Paramecium, and the secretion of insulin from pancreatic cells, immune modulators from lymphocytes, and chemical transmitters from neurons. In animal cells, serine/threonine kinases including cAMP-dependent protein kinase, protein kinase C and calmodulin kinases have been implicated in calcium-signal transduction leading to regulated secretion. Although plants and protozoa also regulate secretion by means of intracellular calcium, the method by which these signals are relayed has not been explained. Here we show that the Toxoplasma gondii calcium-dependent protein kinase 1 (TgCDPK1) is an essential regulator of calcium-dependent exocytosis in this opportunistic human pathogen. Conditional suppression of TgCDPK1 revealed that it controls calcium-dependent secretion of specialized organelles called micronemes, resulting in a block of essential phenotypes including parasite motility, host-cell invasion, and egress. These phenotypes were recapitulated by using a chemical biology approach in which pyrazolopyrimidine-derived compounds specifically inhibited TgCDPK1 and disrupted the parasite's life cycle at stages dependent on microneme secretion. Inhibition was specific to TgCDPK1, because expression of a resistant mutant kinase reversed sensitivity to the inhibitor. TgCDPK1 is conserved among apicomplexans and belongs to a family of kinases shared with plants and ciliates, suggesting that related CDPKs may have a function in calcium-regulated secretion in other organisms. Because this kinase family is absent from mammalian hosts, it represents a validated target that may be exploitable for chemotherapy against T. gondii and related apicomplexans.

Dataset Information

Toxoplasma DJ-1 Regulates Organelle Secretion by a Direct Interaction with Calcium-Dependent Protein Kinase 1.

Publications

Toxoplasma DJ-1 Regulates Organelle Secretion by a Direct Interaction with Calcium-Dependent Protein Kinase 1.

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