Limits...
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.

Show MeSH

Related in: MedlinePlus

Model for processing of procyclin and trans-sialidase (TS) in wild type and GPI mutant trypanosomes. (A) The successful GPI anchoring of procyclins and TS in the ER (bottom) and subsequent addition of branched poly-N-acetyl-lactosamine side chains in the Golgi (middle) lead to the surface expression of GPI-anchored procyclins and TS. The surface-expressed TS sialylates GPI side chains on procyclins and free GPIs. (B) The lack of TbGPI10 leads to the formation of a truncated GPI precursor that cannot be transferred to nascent procyclins and TS. Therefore, the transamidase (TA) produces soluble forms of procyclins and TS that are secreted from the cell. Thus, cell surface–free GPIs that have been modified with poly-N-acetyl-lactosamine structures become sialylated by soluble TS. (C) The lack of TbGPI8, the catalytic subunit of transamidase, prevents any processing of procyclins and TS, probably resulting in their intracellular degradation. Unused intact PP1 glycolipids are processed in the Golgi with branched poly-N-acetyl-lactosamine side chains and expressed on the cell surface. The free GPIs are not sialylated due to the absence of cell surface TS. However, when GPI8KO cells are transformed with a gene-encoding, soluble, secreted form of TS (sTS) (right), the surface of GPI8KO cells becomes sialylated. Mannose, galactose, inositol, N-acetylglucosamine, glucosamine, and sialic acid are represented by open circles, closed circles, dotted circles, open squares, dotted squares, and diamonds, respectively. Procyclins and GPI attachment signal peptides are depicted as black and dotted rectangles, respectively.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2211819&req=5

fig2: Model for processing of procyclin and trans-sialidase (TS) in wild type and GPI mutant trypanosomes. (A) The successful GPI anchoring of procyclins and TS in the ER (bottom) and subsequent addition of branched poly-N-acetyl-lactosamine side chains in the Golgi (middle) lead to the surface expression of GPI-anchored procyclins and TS. The surface-expressed TS sialylates GPI side chains on procyclins and free GPIs. (B) The lack of TbGPI10 leads to the formation of a truncated GPI precursor that cannot be transferred to nascent procyclins and TS. Therefore, the transamidase (TA) produces soluble forms of procyclins and TS that are secreted from the cell. Thus, cell surface–free GPIs that have been modified with poly-N-acetyl-lactosamine structures become sialylated by soluble TS. (C) The lack of TbGPI8, the catalytic subunit of transamidase, prevents any processing of procyclins and TS, probably resulting in their intracellular degradation. Unused intact PP1 glycolipids are processed in the Golgi with branched poly-N-acetyl-lactosamine side chains and expressed on the cell surface. The free GPIs are not sialylated due to the absence of cell surface TS. However, when GPI8KO cells are transformed with a gene-encoding, soluble, secreted form of TS (sTS) (right), the surface of GPI8KO cells becomes sialylated. Mannose, galactose, inositol, N-acetylglucosamine, glucosamine, and sialic acid are represented by open circles, closed circles, dotted circles, open squares, dotted squares, and diamonds, respectively. Procyclins and GPI attachment signal peptides are depicted as black and dotted rectangles, respectively.

Mentions: A significant difference between GPI10KO and GPI8KO cells should be in the structures of their GPIs. TbGPI10 encodes a mannosyltransferase that adds the third mannose to GPI (12), which suggests that GPI10KO cells have truncated “nonprotein-linked” GPI with only two mannoses (Fig. 2 B). TbGPI8 encodes a catalytic subunit of GPI transamidase (11), suggesting that GPI8KO cells have nonprotein-linked GPI with a complete core (Fig. 2 C). Vassella et al. reported that procyclic trypanosomes completely lacking all procyclin genes express free GPI on their surface (24). Lillico et al. reported that some of the nonprotein-linked GPIs are on the surface of the GPI8KO (17). We found that GPI10KO as well as GPI8KO trypanosomes express abundant nonprotein-linked GPIs on their cell surface (unpublished data). To determine the carbohydrate compositions of these free GPIs, we isolated them from GPI10KO and GPI8KO cells, and as a reference, intact procyclins from the wild-type cells. The procyclins had the carbohydrate composition expected from their known structures (Table I) . The free GPI from GPI10KO cells had ∼2 mol of mannose per mole of myo-inositol and, in addition, galactose, N-acetylglucosamine, and sialic acid. The latter sugars are components of the sialylated poly-N-acetyl-lactosamine side chains found on procyclins (25) and free GPIs from procyclin mutant (24) and GPI10KO (unpublished data). In contrast, the free GPIs from GPI8KO cells had mannose, galactose, and N-acetylglucosamine, but no sialic acid. Because it was reported that the GPI anchors are the major sialylated molecules on procyclic form T. brucei (14, 15), we determined the total sialic acid contents of those cells. Wild-type and GPI10KO cells had 5–6 × 106 and 2.5 × 106 sialic acid molecules per cell, respectively, whereas GPI8KO cells had no detectable sialic acid. Therefore, a lack of sialic acid is a major phenotype of GPI8KO cells.


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)

Model for processing of procyclin and trans-sialidase (TS) in wild type and GPI mutant trypanosomes. (A) The successful GPI anchoring of procyclins and TS in the ER (bottom) and subsequent addition of branched poly-N-acetyl-lactosamine side chains in the Golgi (middle) lead to the surface expression of GPI-anchored procyclins and TS. The surface-expressed TS sialylates GPI side chains on procyclins and free GPIs. (B) The lack of TbGPI10 leads to the formation of a truncated GPI precursor that cannot be transferred to nascent procyclins and TS. Therefore, the transamidase (TA) produces soluble forms of procyclins and TS that are secreted from the cell. Thus, cell surface–free GPIs that have been modified with poly-N-acetyl-lactosamine structures become sialylated by soluble TS. (C) The lack of TbGPI8, the catalytic subunit of transamidase, prevents any processing of procyclins and TS, probably resulting in their intracellular degradation. Unused intact PP1 glycolipids are processed in the Golgi with branched poly-N-acetyl-lactosamine side chains and expressed on the cell surface. The free GPIs are not sialylated due to the absence of cell surface TS. However, when GPI8KO cells are transformed with a gene-encoding, soluble, secreted form of TS (sTS) (right), the surface of GPI8KO cells becomes sialylated. Mannose, galactose, inositol, N-acetylglucosamine, glucosamine, and sialic acid are represented by open circles, closed circles, dotted circles, open squares, dotted squares, and diamonds, respectively. Procyclins and GPI attachment signal peptides are depicted as black and dotted rectangles, respectively.
© Copyright Policy
Related In: Results  -  Collection

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

fig2: Model for processing of procyclin and trans-sialidase (TS) in wild type and GPI mutant trypanosomes. (A) The successful GPI anchoring of procyclins and TS in the ER (bottom) and subsequent addition of branched poly-N-acetyl-lactosamine side chains in the Golgi (middle) lead to the surface expression of GPI-anchored procyclins and TS. The surface-expressed TS sialylates GPI side chains on procyclins and free GPIs. (B) The lack of TbGPI10 leads to the formation of a truncated GPI precursor that cannot be transferred to nascent procyclins and TS. Therefore, the transamidase (TA) produces soluble forms of procyclins and TS that are secreted from the cell. Thus, cell surface–free GPIs that have been modified with poly-N-acetyl-lactosamine structures become sialylated by soluble TS. (C) The lack of TbGPI8, the catalytic subunit of transamidase, prevents any processing of procyclins and TS, probably resulting in their intracellular degradation. Unused intact PP1 glycolipids are processed in the Golgi with branched poly-N-acetyl-lactosamine side chains and expressed on the cell surface. The free GPIs are not sialylated due to the absence of cell surface TS. However, when GPI8KO cells are transformed with a gene-encoding, soluble, secreted form of TS (sTS) (right), the surface of GPI8KO cells becomes sialylated. Mannose, galactose, inositol, N-acetylglucosamine, glucosamine, and sialic acid are represented by open circles, closed circles, dotted circles, open squares, dotted squares, and diamonds, respectively. Procyclins and GPI attachment signal peptides are depicted as black and dotted rectangles, respectively.
Mentions: A significant difference between GPI10KO and GPI8KO cells should be in the structures of their GPIs. TbGPI10 encodes a mannosyltransferase that adds the third mannose to GPI (12), which suggests that GPI10KO cells have truncated “nonprotein-linked” GPI with only two mannoses (Fig. 2 B). TbGPI8 encodes a catalytic subunit of GPI transamidase (11), suggesting that GPI8KO cells have nonprotein-linked GPI with a complete core (Fig. 2 C). Vassella et al. reported that procyclic trypanosomes completely lacking all procyclin genes express free GPI on their surface (24). Lillico et al. reported that some of the nonprotein-linked GPIs are on the surface of the GPI8KO (17). We found that GPI10KO as well as GPI8KO trypanosomes express abundant nonprotein-linked GPIs on their cell surface (unpublished data). To determine the carbohydrate compositions of these free GPIs, we isolated them from GPI10KO and GPI8KO cells, and as a reference, intact procyclins from the wild-type cells. The procyclins had the carbohydrate composition expected from their known structures (Table I) . The free GPI from GPI10KO cells had ∼2 mol of mannose per mole of myo-inositol and, in addition, galactose, N-acetylglucosamine, and sialic acid. The latter sugars are components of the sialylated poly-N-acetyl-lactosamine side chains found on procyclins (25) and free GPIs from procyclin mutant (24) and GPI10KO (unpublished data). In contrast, the free GPIs from GPI8KO cells had mannose, galactose, and N-acetylglucosamine, but no sialic acid. Because it was reported that the GPI anchors are the major sialylated molecules on procyclic form T. brucei (14, 15), we determined the total sialic acid contents of those cells. Wild-type and GPI10KO cells had 5–6 × 106 and 2.5 × 106 sialic acid molecules per cell, respectively, whereas GPI8KO cells had no detectable sialic acid. Therefore, a lack of sialic acid is a major phenotype of GPI8KO cells.

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