TY - JOUR
T1 - Novel Thioredoxin-like proteins are components of a protein complex coating the cortical microtubules of Toxoplasma gondii
AU - Liu, Jun
AU - Wetzel, Laura
AU - Zhang, Ying
AU - Nagayasu, Eiji
AU - Ems-Mcclung, Stephanie
AU - Florens, Laurence
AU - Hu, Ke
PY - 2013
Y1 - 2013
N2 - Microtubules are versatile biopolymers that support numerous vital cellular functions in eukaryotes. The specific properties of microtubules are dependent on distinct microtubule-associated proteins, as the tubulin subunits and microtubule structure are exceptionally conserved. Highly specialized microtubule-containing assemblies are often found in protists, which are rich sources for novel microtubule-associated proteins. A protozoan parasite, Toxoplasma gondii, possesses several distinct tubulin containing structures, including 22 microtubules closely associated with the cortical membrane. Early ultrastructural studies have shown that the cortical microtubules are heavily decorated with associating proteins. However, little is known about the identities of these proteins. Here, we report the discovery of a novel protein, TrxL1 (for Thioredoxin-Like protein 1), and an associating complex that coats the cortical microtubules. TrxL1 contains a thioredoxin-like fold. To visualize its localization in live parasites by fluorescence, we replaced the endogenous TrxL1 gene with an mEmeraldFP-TrxL1 fusion gene. Structured illumination-based superresolution imaging of this parasite line produced a detailed view of the microtubule cytoskeleton. Despite its stable association with the cortical microtubules in the parasite, TrxL1 does not seem to bind to microtubules directly. Coimmunoprecipitation experiments showed that TrxL1 associates with a protein complex containing SPM1, a previously reported microtubule-associated protein in T. gondii. We also found that SPM1 recruits TrxL1 to the cortical microtubules. Besides SPM1, several other novel proteins are found in the TrxL1-containing complex, including TrxL2, a close homolog of TrxL1. Thus, our results reveal for the first time a microtubule-associated complex in T. gondii.
AB - Microtubules are versatile biopolymers that support numerous vital cellular functions in eukaryotes. The specific properties of microtubules are dependent on distinct microtubule-associated proteins, as the tubulin subunits and microtubule structure are exceptionally conserved. Highly specialized microtubule-containing assemblies are often found in protists, which are rich sources for novel microtubule-associated proteins. A protozoan parasite, Toxoplasma gondii, possesses several distinct tubulin containing structures, including 22 microtubules closely associated with the cortical membrane. Early ultrastructural studies have shown that the cortical microtubules are heavily decorated with associating proteins. However, little is known about the identities of these proteins. Here, we report the discovery of a novel protein, TrxL1 (for Thioredoxin-Like protein 1), and an associating complex that coats the cortical microtubules. TrxL1 contains a thioredoxin-like fold. To visualize its localization in live parasites by fluorescence, we replaced the endogenous TrxL1 gene with an mEmeraldFP-TrxL1 fusion gene. Structured illumination-based superresolution imaging of this parasite line produced a detailed view of the microtubule cytoskeleton. Despite its stable association with the cortical microtubules in the parasite, TrxL1 does not seem to bind to microtubules directly. Coimmunoprecipitation experiments showed that TrxL1 associates with a protein complex containing SPM1, a previously reported microtubule-associated protein in T. gondii. We also found that SPM1 recruits TrxL1 to the cortical microtubules. Besides SPM1, several other novel proteins are found in the TrxL1-containing complex, including TrxL2, a close homolog of TrxL1. Thus, our results reveal for the first time a microtubule-associated complex in T. gondii.
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U2 - 10.1128/EC.00082-13
DO - 10.1128/EC.00082-13
M3 - Article
C2 - 23873863
AN - SCOPUS:84888233751
SN - 1535-9778
VL - 12
SP - 1588
EP - 1599
JO - Eukaryotic Cell
JF - Eukaryotic Cell
IS - 12
ER -