Amylopectin biogenesis and characterization in the protozoan parasite Toxoplasma gondii, the intracellular development of which is restricted in the HepG2 cell line

Guérardel, Yann; Leleu, Denis; Coppin, Alexandra; Liénard, Luc; Slomianny, Christian; Strecker, Gérard; Ball, Steven; Tomavo, Stanislas

doi:10.1016/j.micinf.2004.09.007

Cited by 59 publications

(53 citation statements)

References 38 publications

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“…Lipid species were identified by mild base and acid treatments ( Figure S4C, Figure S5C). is normally increased in slow-growing parasite stages (Gué rardel et al, 2005;Lin et al, 2011), suggesting that the decreased flux into amylopectin synthesis following downregulation of TgFBP2 expression is a direct consequence of reduced flux into glycan synthesis and not due to slow parasite growth. This was further confirmed by independently arresting parasite growth with 5-fluorodeoxyuridine (FUDR) ( Figure S5E).…”

Section: Loss Of Tgfbp2 Results In General Dysregulation Of Hexose Phmentioning

confidence: 99%

A Toxoplasma gondii Gluconeogenic Enzyme Contributes to Robust Central Carbon Metabolism and Is Essential for Replication and Virulence

Blume

Nitzsche

Sternberg

et al. 2015

Cell Host & Microbe

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The expression of gluconeogenic enzymes is typically repressed when glucose is available. The protozoan parasite Toxoplasma gondii utilizes host glucose to sustain high rates of intracellular replication. However, despite their preferential utilization of glucose, intracellular parasites constitutively express two isoforms of the gluconeogenic enzyme fructose 1,6-bisphosphatase (TgFBP1 and TgFBP2). The rationale for constitutive expression of FBPases in T. gondii remains unclear. We find that conditional knockdown of TgFBP2 results in complete loss of intracellular growth in vitro under glucose-replete conditions and loss of acute virulence in mice. TgFBP2 deficiency was rescued by expression of catalytically active FBPase and was associated with altered glycolytic and mitochondrial TCA cycle fluxes, as well as dysregulation of glycolipid, amylopectin, and fatty acid biosynthesis. Futile cycling between gluconeogenic and glycolytic enzymes may constitute a regulatory mechanism that allows T. gondii to rapidly adapt to changes in nutrient availability in different host cells.

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Section: Loss Of Tgfbp2 Results In General Dysregulation Of Hexose Phmentioning

confidence: 99%

A Toxoplasma gondii Gluconeogenic Enzyme Contributes to Robust Central Carbon Metabolism and Is Essential for Replication and Virulence

Blume

Nitzsche

Sternberg

et al. 2015

Cell Host & Microbe

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“…The mutant parasites had all the hallmarks of tachyzoites, however, they accumulated amylopectin granules in their cytoplasm (Fig. 8A, panel c), which is a characteristic of tissue cyst forms (bradyzoites) that grow very slowly and rely on sugar stores for glycolysis and gluconeogenesis (48). The presence of these glucose storage granules suggests that the ⌬lcat parasites exhibited signs of stress.…”

Section: Toxoplasma Lacking Lcat Show Delayed Egress Whereas Parasitementioning

confidence: 99%

A Lipolytic Lecithin:Cholesterol Acyltransferase Secreted by Toxoplasma Facilitates Parasite Replication and Egress

Pszenny

Ehrenman

Romano

et al. 2016

Journal of Biological Chemistry

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The protozoan parasite Toxoplasma gondii develops within a parasitophorous vacuole (PV) in mammalian cells, where it scavenges cholesterol. When cholesterol is present in excess in its environment, the parasite expulses this lipid into the PV or esterifies it for storage in lipid bodies. Here, we characterized a unique T. gondii homologue of mammalian lecithin:cholesterol acyltransferase (LCAT), a key enzyme that produces cholesteryl esters via transfer of acyl groups from phospholipids to the 3-OH of free cholesterol, leading to the removal of excess cholesterol from tissues. TgLCAT contains a motif characteristic of serine lipases "AHSLG" and the catalytic triad consisting of serine, aspartate, and histidine (SDH) from LCAT enzymes. TgL-CAT is secreted by the parasite, but unlike other LCAT enzymes it is cleaved into two proteolytic fragments that share the residues of the catalytic triad and need to be reassembled to reconstitute enzymatic activity. TgLCAT uses phosphatidylcholine as substrate to form lysophosphatidylcholine that has the potential to disrupt membranes. The released fatty acid is transferred to cholesterol, but with a lower transesterification activity than mammalian LCAT. TgLCAT is stored in a subpopulation of dense granule secretory organelles, and following secretion, it localizes to the PV and parasite plasma membrane. LCAT-null parasites have impaired growth in vitro, reduced virulence in animals, and exhibit delays in egress from host cells. Parasites overexpressing LCAT show increased virulence and faster egress. These observations demonstrate that TgLCAT influences the outcome of an infection, presumably by facilitating replication and egress depending on the developmental stage of the parasite.The phospholipase A 2 (PLA 2 ) 2 family of serine lipases comprises more than 30 enzymes in mammals. The PLA 2 members hydrolyze the sn-2 ester of phospholipids, yielding lysophospholipid and releasing a fatty acid (1). Approximately one-third of the PLA 2 family members are secreted from cells and display various localizations post-secretion, reflecting their specialized biological functions (2). Among the secretory PLA 2 , lecithin: cholesterol acyltransferase (LCAT; EC 2.3.1.43) is characterized by dual activity, PLA 2 and acyltransferase. In mammals, this enzyme catalyzes the transacylation of the sn-2 fatty acid liberated from various phospholipids (e.g. phosphatidylcholine or phosphatidylethanolamine) to the 3-␤-hydroxyl group on the A-ring of cholesterol, thereby forming cholesteryl esters (3-5). The primary sequence of LCAT is well conserved between mammalian species (6). A structural model for LCAT predicts the conformation of a catalytic triad formed by SerAsp-His residues involved in the phospholipase reaction (7). Mammalian LCATs are primarily expressed in the liver and secreted to the plasma where they circulate in association with HDL (8). These enzymes are components of the reverse cholesterol transport pathway by which cholesterol from peripheral cells is delivered to the liver f...

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“…These particles present a characteristic shape. Those protozoa, which are members of the Apicomplexa group, are able to accumulate amilopectin granules which appear as rounded to ovoid structures with a mean diameter of xxxx m [133]. Since the biogenesis of these structures involves the participation of several enzymes this process may also constitute a drug target, especially in the case of amilopectin granules, a structure not found in animal cells.…”

Section: Polysaccharide Granulesmentioning

confidence: 99%

An Introduction to the Structural Organization of Parasitic Protozoa

Souza¹

2008

CPD

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As eukaryotic cells, protozoa present a classical structural organization where most of the structures and organelles typical of mammalian cells are found. However, even for usual organelles these organisms present structural diversity. In addition, some of the protozoa structures, such as the mitochondria, peroxisomes and even the Golgi complex, are not observed. On the other hand, new organelles such as the hydrogenosomes, mitosomes, Apicoplast, kinetoplast, glycosomes (specialized peroxisomes), rhoptries, micronemes and dense granules, are characteristic features of some protozoa. Also, several unusual cytoskeletal structures, some of them made of yet uncharacterized proteins, are seen in these eukaryotic microorganisms. Further characterization of these structures indicates that they contain special enzymes involved in distinct metabolic pathways making them potential targets for the development of new anti parasite drugs.

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Amylopectin biogenesis and characterization in the protozoan parasite Toxoplasma gondii, the intracellular development of which is restricted in the HepG2 cell line

Cited by 59 publications

References 38 publications

A Toxoplasma gondii Gluconeogenic Enzyme Contributes to Robust Central Carbon Metabolism and Is Essential for Replication and Virulence

A Toxoplasma gondii Gluconeogenic Enzyme Contributes to Robust Central Carbon Metabolism and Is Essential for Replication and Virulence

A Lipolytic Lecithin:Cholesterol Acyltransferase Secreted by Toxoplasma Facilitates Parasite Replication and Egress

An Introduction to the Structural Organization of Parasitic Protozoa

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