Fig 1.
brucei life cycle indicating characteristic gene expression differences between the stages.
Diagram of T. The slender BFs proliferate in the blood, express VSGs, and metabolize glucose as the main energy source and develop into nondividing stumpy BFs that cease VSG expression and express PAD1. The stumpy forms develop into PFs that proliferate in the fly gut, express EPs and GPEETs, and primarily generate energy via oxphos. The PFs develop into EFs in the salivary gland that express BARPs and subsequently develop into infective MFs that resume VSG expression. BARPs, brucei alanine-rich proteins; BFs, bloodstream forms; EFs, epimastigote forms; EPs, procyclin rich in Glu-Pro repeats; GPEETs, procyclin rich in Glu-Pro-Glu-Glu-Thr repeats; MFs, metacyclic forms; oxphos, oxidative phosphorylation; PAD1, proteins associated with differentiation 1; PFs, procyclic forms; VSGs, variant surface glycoproteins.
Fig 2.
Overview of the PI system in T. brucei.
(A) Diagram showing numbering of inositol positions that can be phosphorylated, dephosphorylated, or pyrophosphorylated. Positions 1, 4, and 5 are phosphorylated in IP3 (position 5 is shown in red) and is shown as an example. (B) Simplified diagram showing lipid conjugated (in black) and soluble (in blue) metabolites and enzyme activities for the metabolite interconversions. See Table 1 for the list of the enzymes (and their abbreviations) found in T. brucei. PLC cleavage releases IP3 from the lipid. Inositol can be synthesized from glucose-6-phosphate by INOS or transported as MIS, and PI is synthesized by PIS. (C) PI gene homologs in prokaryotes, protozoa, fungi, and metazoa. The numbers of homologous PI genes are indicated by the circle sizes in each organism. The general roles of the enzymes in synthesis, SGL, PI, or IP kinase (PIK or IPK) and IP or PI phosphatase (IP/PI Pase) are labeled and represented by different colors. IP/PI Pase indicate enzymes that can dephosphorylate IPs and/or PIs. The organisms are Homo sapiens (H. sap), Arabidopsis thaliana (A. tha), Drosophila melanogaster (D. mel), Saccharomyces cerevisiae (S. cer), T. brucei (T. bru), Plasmodium falciparum (P. fal), Giardia lamblia (G. lam), Mycobacterium tuberculosis (M. tub), Escherichia coli (E. col), and Thermus thermophilus (T. the). CDS, CDP-diacylglycerol synthetase; DK, diacylglycerol kinase; IMPA, Inositol-1-monophosphatase; IMPase, inositol (1,4) monophosphatase; INOS, inositol-3-phosphate synthase; INPP1, inositol polyphosphate-1-phosphatase; INPP4, inositol polyphosphate-4-phosphatase; INPP5, inositol polyphosphate-5-phosphatase; IP, inositol phosphate; IPK, inositol polyphosphate kinase; IPMK, inositol polyphosphate multikinase; IPPK, inositol-pentakisphosphate 2-kinase; IPTK, inositol trisphosphate 5/6 kinase; IP3, inositol trisphosphate; IP3R, inositol 1,4,5-triphosphate receptor; IP5Pase, inositol polyphosphate 5-phosphatase; IP6K, inositol hexakisphosphate kinase; MIOX, myo-inositol oxygenase; MIS, myo-inositol-1-phosphate synthase; MIT, myo-inositol/proton symporter; MTM, phosphatidylinositol-3-phosphatase myotubularin; PI, phosphatidylinositol; PIK, phosphatidylinositol kinases; PIP2, phosphatidylinositol 4,5-bisphosphate; PIP5K, phosphatidylinositol 4-phosphate 5-kinase; PIP5Pase, phosphatidylinositol 5-phosphatase; PIS, phosphatidylinositol synthase; PI3K, phosphatidylinositol 3-kinase; PI4K, phosphatidylinositol 4-kinase; PLC, phospholipase C; SGL, signaling; SYJ, phosphatidylinositol 5-phosphatase synaptojanin.
Table 1.
PI system genes of T. brucei.
Fig 3.
Subcellular immunofluorescence localization of PI enzymes in T. brucei slender BF.
V5-tagged PIP5K2 (A), CDS (B), or IP1Pase (C) were expressed from rDNA locus upon induction with tetracycline and stained green with anti-V5 fluorescein-conjugated monoclonal antibodies. Mitochondria are stained red with mitoTracker, DNA is stained blue with DAPI, and DIC indicates differential interference contrast. Arrows indicate PI enzyme staining in black and white in expanded regions. The cells were permeabilized with 0.2% NP40 except as indicated as NP. BF, bloodstream form; CDS, CDP-diacylglycerol synthetase; DAPI, 4′,6-diamidino-2-phenylindole; DIC, differential interference contrast; ER, endoplasmic reticulum; Gg, Golgi; IP1Pase, inositol polyphosphate 1-phosphatase; NP, non-permeabilized; PI, phosphatidylinositol; PIP5K2, phosphatidylinositol 4-phosphate 5-kinase 2; PM, plasma membrane.