Profiling of myristoylation in Toxoplasma gondii reveals an N-myristoylated protein important for host cell penetration

Abstract

<jats:p>N-myristoylation is a ubiquitous class of protein lipidation across eukaryotes and N-myristoyl transferase (NMT) has been proposed as an attractive drug target in several pathogens. Myristoylation often primes for subsequent palmitoylation and stable membrane attachment, however, growing evidence suggests additional regulatory roles for myristoylation on proteins. Here we describe the myristoylated proteome of Toxoplasma gondii using chemoproteomic methods and show that a small-molecule NMT inhibitor developed against related Plasmodium spp. is also functional in Toxoplasma. We identify myristoylation on a transmembrane protein, the microneme protein 7 (MIC7), which enters the secretory pathway in an unconventional fashion with the myristoylated N-terminus facing the lumen of the micronemes. MIC7 and its myristoylation play a crucial role in the initial steps of invasion, likely during the interaction with and penetration of the host cell. Myristoylation of secreted eukaryotic proteins represents a substantial expansion of the functional repertoire of this co-translational modification.</jats:p>

A Conditional Protein Degradation System To Study Essential Gene Function in Cryptosporidium parvum

“…It is also possible that CDPK1 levels are post-transcriptionally or post-translationally regulated and the DDD system may be perturbating this regulation, thus resulting in incomplete knockdown of CDPK1 in the absence of TMP or aberrant expression in sexual developmental stages during the parasite cycle. In other apicomplexan parasites, post-translational modification such as myristoylation of signaling effectors has been demonstrated to play critical roles in cellular localization and regulating key parasite functions such as microneme secretion, invasion, and egress ( 39 , 55 – 57 ). Since there is a predicted N-myristoylation site in C. parvum CDPK1 ( 58 ), it is possible that post-translational modification of this protein may be required for proper localization and function.…”

Faculty Opinions recommendation of A Conditional Protein Degradation System To Study Essential Gene Function in Cryptosporidium parvum.

“…It is also possible that CDPK1 levels are posttranscriptionally or post-translationally regulated and the DDD system may be perturbating this regulation, thus resulting in incomplete knockdown of CDPK1 in the absence of TMP or aberrant expression in sexual developmental stages during the parasite cycle. In other apicomplexan parasites, post-translational modification such as myristoylation of signaling effectors has been demonstrated to play critical roles in cellular localization and regulating key parasite functions such as microneme secretion, invasion, and egress (39,(55)(56)(57). Since there is a predicted N-myristoylation site in C. parvum CDPK1 (58), it is possible that post-translational modification of this protein may be required for proper localization and function.…”

Unraveling the Elusive Rhoptry Exocytic Mechanism of Apicomplexa

“…This restores the cytosolic Ca 2+ to basal levels, and also promotes the release of rhoptry proteins [8]. MIC secretion is also important for triggering rhoptry discharge in T. gondii, where the relevant microneme factors include transmembrane protein AMA1 [39], MIC8 [7], possibly CLAMP [40], and MIC7 [41]. The roles of MICs in this process is not limited to extracellular binding, since, in P. falciparum, the cytoplasmic tail of PfEBA175 was found to be required for a GPA-dependent host-cell invasion pathway [42].…”