Phosphorylation of a Toxoplasma gondii tyrosine transporter by calcium-dependent kinase 3 is important for parasite fitness

Abstract

22Toxoplasma gondii parasites rapidly exit their host cell when exposed to calcium 23 ionophores. The calcium-dependent protein kinase 3 (TgCDPK3) was previously 24 identified as a key mediator in this process, as TgCDPK3 knockout (∆cdpk3) (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/339671 doi: bioRxiv preprint first posted online Jun. 5, 2018; 3 allow the parasites to sense and respond rapidly to their environment. While some 46 key kinases and secondary messengers within these pathways have been 47 identified, functional analysis of non-kinases has been very limited. This is 48 especially true for candidates that are not predicted to play a role in active motility 49 or are not known to function in established signalling pathways. Here we have 50 followed up on an unexpected target of the T. gondii calcium-dependent kinase 3 51 (TgCDPK3), a plant-like calcium dependent kinase, that was previously shown to 52 play an important role in calcium-mediated exit from the host cell. We show that, 53 in addition to controlling motility of the parasite (as previously shown), TgCDPK3 54 phosphorylates an essential tyrosine transporter in the plasma membrane. 55Mutational analysis of the phosphorylation sites demonstrates an important role 56 in maintaining parasite fitness, thus demonstrating that TgCDPK3 plays a 57 pleiotropic role in controlling both egress and metabolism. 58 59

Metabolic interactions between Toxoplasma gondii and its host

“…Besides glutamine, a range of amino acids are imported, as shown recently by gas chromatography–coupled mass spectrometry (GC/MS). These include alanine, valine, leucine, isoleucine, proline, glycine, serine, threonine, methionine, and tyrosine 24 , 27 . Phenylalanine import 28 was observed by using Raman spectroscopy.…”

“…Recently, several amino acid transporters have been identified as part of a transporter family that appears to be specific to apicomplexans 24 . Arginine and tyrosine transport activity has been assigned to T. gondii apicomplexan amino acid transporter 1 and 5-3 (TgApiAT1 and TgApiAT5-3), respectively 24 , 27 , 29 . Other amino acids such as histidine, lysine, branched-chain amino acids, and cysteine or methionine have been considered to be essential 18 but this remains to be experimentally verified.…”