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Surface sialic acids taken from the host allow trypanosome survival in tsetse fly vectors.

Nagamune K, Acosta-Serrano A, Uemura H, Brun R, Kunz-Renggli C, Maeda Y, Ferguson MA, Kinoshita T - J. Exp. Med. (2004)

Bottom Line: Here, we show that for successful survival in Tsetse flies, the trypanosomes use trans-sialidase to transfer sialic acids that they cannot synthesize from host's glycoconjugates to the glycosylphosphatidylinositols (GPIs), which are abundantly expressed on their surface.Trypanosomes lacking sialic acids due to a defective generation of GPI-anchored trans-sialidase could not survive in the intestine, but regained the ability to survive when sialylated by means of soluble trans-sialidase.Thus, surface sialic acids appear to protect the parasites from the digestive and trypanocidal environments in the midgut of Tsetse flies.

View Article: PubMed Central - PubMed

Affiliation: Dept. of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan.

ABSTRACT
The African trypanosome Trypanosoma brucei, which causes sleeping sickness in humans and Nagana disease in livestock, is spread via blood-sucking Tsetse flies. In the fly's intestine, the trypanosomes survive digestive and trypanocidal environments, proliferate, and translocate into the salivary gland, where they become infectious to the next mammalian host. Here, we show that for successful survival in Tsetse flies, the trypanosomes use trans-sialidase to transfer sialic acids that they cannot synthesize from host's glycoconjugates to the glycosylphosphatidylinositols (GPIs), which are abundantly expressed on their surface. Trypanosomes lacking sialic acids due to a defective generation of GPI-anchored trans-sialidase could not survive in the intestine, but regained the ability to survive when sialylated by means of soluble trans-sialidase. Thus, surface sialic acids appear to protect the parasites from the digestive and trypanocidal environments in the midgut of Tsetse flies.

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Related in: MedlinePlus

Both infectious ability to Tsetse flies and trans-sialidase activity are greatly decreased in GPI8KO procyclics. (A) Different infectivities to Tsetse flies of GPI10KO and GPI8KO T. brucei. Wild-type, GPI10KO, and GPI8KO procyclics (WT, 10, and 8, respectively) were fed to Tsetse flies. After 24 d, flies were dissected, and the infectivities were scored as heavy (black area, 100–300 trypanosomes per field in 10 fields with the 20× objective), intermediate (shaded area, between “heavy” and “weak”), weak (dotted area, <3 three trypanosomes per field), and negative (white area, no trypanosome detectable). The number of flies in each group is indicated above each bar. (B) Trans-sialidase activity of cell lysates from 108 of wild-type, GPI8KO, and GPI10KO parasites (WT, 8, and 10, respectively) were determined. Trans-sialidase activity is expressed in microunits. (C) Release of trans-sialidase from GPI10KO procyclics into culture supernatant. Wild-type (□), GPI8KO (×), and GPI10KO (○) procyclics were inoculated at 105 cells/ml and cultured for 3 d. Every 12 h, trans-sialidase in the culture supernatant (top) and cell density (bottom, ×105/ml) were determined. Trans-sialidase activity in the supernatant was normalized by cell density and is expressed in μU/105 cells.
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fig1: Both infectious ability to Tsetse flies and trans-sialidase activity are greatly decreased in GPI8KO procyclics. (A) Different infectivities to Tsetse flies of GPI10KO and GPI8KO T. brucei. Wild-type, GPI10KO, and GPI8KO procyclics (WT, 10, and 8, respectively) were fed to Tsetse flies. After 24 d, flies were dissected, and the infectivities were scored as heavy (black area, 100–300 trypanosomes per field in 10 fields with the 20× objective), intermediate (shaded area, between “heavy” and “weak”), weak (dotted area, <3 three trypanosomes per field), and negative (white area, no trypanosome detectable). The number of flies in each group is indicated above each bar. (B) Trans-sialidase activity of cell lysates from 108 of wild-type, GPI8KO, and GPI10KO parasites (WT, 8, and 10, respectively) were determined. Trans-sialidase activity is expressed in microunits. (C) Release of trans-sialidase from GPI10KO procyclics into culture supernatant. Wild-type (□), GPI8KO (×), and GPI10KO (○) procyclics were inoculated at 105 cells/ml and cultured for 3 d. Every 12 h, trans-sialidase in the culture supernatant (top) and cell density (bottom, ×105/ml) were determined. Trans-sialidase activity in the supernatant was normalized by cell density and is expressed in μU/105 cells.

Mentions: GPI-anchored proteins, such as procyclins, have a signal peptide for GPI attachment at their COOH termini. In the ER, GPI transamidase replaces the signal peptide with a preassembled GPI. The GPI transamidase of T. brucei consists of five subunits as follows: TbGPI8, TbGAA1, TbGPI16, TTA1, and TTA2 (10). TbGPI8 is a catalytic subunit that cleaves the signal peptide (11). GPI, a complex glycolipid, is also synthesized in the ER through sequential additions of components to phosphatidylinositol. TbGPI10 gene encodes α1-2 mannosyltransferase that adds the third mannose to GPI (12). TbGPI10 knockout procyclics (GPI10KO) lost the surface expression of procyclins due to a lack of fully assembled GPI anchors capable of attachment to procyclins and other proteins (12). We showed that procyclin-less GPI10KO survived and proliferated in Tsetse flies, albeit less efficiently than the wild-type parasites, confirming that the protein portions of procyclins play some role but are not essential for their survival (see Fig. 1 A; reference 12).


Surface sialic acids taken from the host allow trypanosome survival in tsetse fly vectors.

Nagamune K, Acosta-Serrano A, Uemura H, Brun R, Kunz-Renggli C, Maeda Y, Ferguson MA, Kinoshita T - J. Exp. Med. (2004)

Both infectious ability to Tsetse flies and trans-sialidase activity are greatly decreased in GPI8KO procyclics. (A) Different infectivities to Tsetse flies of GPI10KO and GPI8KO T. brucei. Wild-type, GPI10KO, and GPI8KO procyclics (WT, 10, and 8, respectively) were fed to Tsetse flies. After 24 d, flies were dissected, and the infectivities were scored as heavy (black area, 100–300 trypanosomes per field in 10 fields with the 20× objective), intermediate (shaded area, between “heavy” and “weak”), weak (dotted area, <3 three trypanosomes per field), and negative (white area, no trypanosome detectable). The number of flies in each group is indicated above each bar. (B) Trans-sialidase activity of cell lysates from 108 of wild-type, GPI8KO, and GPI10KO parasites (WT, 8, and 10, respectively) were determined. Trans-sialidase activity is expressed in microunits. (C) Release of trans-sialidase from GPI10KO procyclics into culture supernatant. Wild-type (□), GPI8KO (×), and GPI10KO (○) procyclics were inoculated at 105 cells/ml and cultured for 3 d. Every 12 h, trans-sialidase in the culture supernatant (top) and cell density (bottom, ×105/ml) were determined. Trans-sialidase activity in the supernatant was normalized by cell density and is expressed in μU/105 cells.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2211819&req=5

fig1: Both infectious ability to Tsetse flies and trans-sialidase activity are greatly decreased in GPI8KO procyclics. (A) Different infectivities to Tsetse flies of GPI10KO and GPI8KO T. brucei. Wild-type, GPI10KO, and GPI8KO procyclics (WT, 10, and 8, respectively) were fed to Tsetse flies. After 24 d, flies were dissected, and the infectivities were scored as heavy (black area, 100–300 trypanosomes per field in 10 fields with the 20× objective), intermediate (shaded area, between “heavy” and “weak”), weak (dotted area, <3 three trypanosomes per field), and negative (white area, no trypanosome detectable). The number of flies in each group is indicated above each bar. (B) Trans-sialidase activity of cell lysates from 108 of wild-type, GPI8KO, and GPI10KO parasites (WT, 8, and 10, respectively) were determined. Trans-sialidase activity is expressed in microunits. (C) Release of trans-sialidase from GPI10KO procyclics into culture supernatant. Wild-type (□), GPI8KO (×), and GPI10KO (○) procyclics were inoculated at 105 cells/ml and cultured for 3 d. Every 12 h, trans-sialidase in the culture supernatant (top) and cell density (bottom, ×105/ml) were determined. Trans-sialidase activity in the supernatant was normalized by cell density and is expressed in μU/105 cells.
Mentions: GPI-anchored proteins, such as procyclins, have a signal peptide for GPI attachment at their COOH termini. In the ER, GPI transamidase replaces the signal peptide with a preassembled GPI. The GPI transamidase of T. brucei consists of five subunits as follows: TbGPI8, TbGAA1, TbGPI16, TTA1, and TTA2 (10). TbGPI8 is a catalytic subunit that cleaves the signal peptide (11). GPI, a complex glycolipid, is also synthesized in the ER through sequential additions of components to phosphatidylinositol. TbGPI10 gene encodes α1-2 mannosyltransferase that adds the third mannose to GPI (12). TbGPI10 knockout procyclics (GPI10KO) lost the surface expression of procyclins due to a lack of fully assembled GPI anchors capable of attachment to procyclins and other proteins (12). We showed that procyclin-less GPI10KO survived and proliferated in Tsetse flies, albeit less efficiently than the wild-type parasites, confirming that the protein portions of procyclins play some role but are not essential for their survival (see Fig. 1 A; reference 12).

Bottom Line: Here, we show that for successful survival in Tsetse flies, the trypanosomes use trans-sialidase to transfer sialic acids that they cannot synthesize from host's glycoconjugates to the glycosylphosphatidylinositols (GPIs), which are abundantly expressed on their surface.Trypanosomes lacking sialic acids due to a defective generation of GPI-anchored trans-sialidase could not survive in the intestine, but regained the ability to survive when sialylated by means of soluble trans-sialidase.Thus, surface sialic acids appear to protect the parasites from the digestive and trypanocidal environments in the midgut of Tsetse flies.

View Article: PubMed Central - PubMed

Affiliation: Dept. of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan.

ABSTRACT
The African trypanosome Trypanosoma brucei, which causes sleeping sickness in humans and Nagana disease in livestock, is spread via blood-sucking Tsetse flies. In the fly's intestine, the trypanosomes survive digestive and trypanocidal environments, proliferate, and translocate into the salivary gland, where they become infectious to the next mammalian host. Here, we show that for successful survival in Tsetse flies, the trypanosomes use trans-sialidase to transfer sialic acids that they cannot synthesize from host's glycoconjugates to the glycosylphosphatidylinositols (GPIs), which are abundantly expressed on their surface. Trypanosomes lacking sialic acids due to a defective generation of GPI-anchored trans-sialidase could not survive in the intestine, but regained the ability to survive when sialylated by means of soluble trans-sialidase. Thus, surface sialic acids appear to protect the parasites from the digestive and trypanocidal environments in the midgut of Tsetse flies.

Show MeSH
Related in: MedlinePlus