Giardia lamblia: Regulation of secretory vesicle formation and loss of ability to reattach during encystation in vitro

Faubert, G M; Reiner, David S.; Gillin, Frances D.

doi:10.1016/0014-4894(91)90080-g

Cited by 50 publications

(45 citation statements)

References 24 publications

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“…Appearance of this activity in encysting cells coincides with that of the other recently described inducible enzymes of Giardia, which collectively synthesize the UDP-GalNAc from endogenous glucose reserves (Macechko et al, 1992). Furthermore, its appearance coincides with the appearance of encystation-specific vesicles (Faubert et al, 1991) and with the appearance of intact Giardia cysts in vitro. This enzyme activity exhibits a very low K m for UDP-GalNAc, suggesting that this enzyme has a high affinity for UDP-GalNAc.…”

Section: Discussionsupporting

confidence: 53%

“…Because of the apparent particle association of CWS activity, it is possible that CWS is associated with encystation-specific vesicles (ESVs) (Faubert et al, 1991) since these vesicles do sediment with a P-fraction under the organelle-preserving conditions of our cellular fractionation procedure (E. L. Jarroll, unpublished observations). Samples tested in the laboratory of Dr Ted Nash, NIH, demonstrated that CWS-containing vesicles react positively with monoclonal antibodies 5-3C, 8G8 and 7D2, which specifically recognize the developmentally induced ESV-associated cyst wall proteins CWP1 and CWP2 (Lujan et al, 1995b;Mowatt et al, 1995;Boone et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

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Cyst wall synthase: N-acetylgalactosaminyltransferase activity is induced to form the novel N-acetylgalactosamine polysaccharide in the Giardia cyst wall

Karr

Jarroll

2004

Microbiology

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Section: Discussionsupporting

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Cyst wall synthase: N-acetylgalactosaminyltransferase activity is induced to form the novel N-acetylgalactosamine polysaccharide in the Giardia cyst wall

Karr

Jarroll

2004

Microbiology

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“…During encystation, trophozoites, which are shaped like a half-pear, round up and lose the ability to re-attach because their flagella and adhesive disc are curled up inside the cyst wall (68). A major challenge of excystation in the duodenum is for the excyzoite to emerge from the cyst wall, recover motility, undergo its first round of cytokinesis, and attach before being carried away by intestinal flow.…”

Section: And This Work)mentioning

confidence: 99%

Calcium Signaling in Excystation of the Early Diverging Eukaryote, Giardia lamblia

Reiner

Hetsko

Meszaros

et al. 2003

Journal of Biological Chemistry

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Excystation of Giardia lamblia, which initiates infection, is a poorly understood but dramatic differentiation induced by physiological signals from the host. Our data implicate a central role for calcium homeostasis in excystation. Agents that alter cytosolic Ca 2؉ levels (1,2-bis(2-aminophenoxy)ethane-N,N,N ,N -tetraacetic acidtetra(acetyloxymethyl) ester, a Ca 2؉ channel blocker, Ca 2؉ ionophores, and thapsigargin) strongly inhibit excystation. Treatment of Giardia with thapsigargin raised intracellular Ca 2؉ levels, and peak Ca 2؉ responses increased with each stage of excystation, consistent with the kinetics of inhibition. Fluorescent thapsigargin localized to a likely Ca 2؉ storage compartment in cysts. The ability to sequester ions in membranebounded compartments is a hallmark of the eukaryotic cell. These studies support the existence of a giardial thapsigargin-sensitive Ca 2؉ storage compartment resembling the sarcoplasmic/endoplasmic reticulum calcium ATPase pump-leak system and suggest that it is important in regulation of differentiation and appeared early in the evolution of eukaryotic cells. Calmodulin antagonists also blocked excystation. The divergent giardial calmodulin localized to the eight flagellar basal bodies/centrosomes, like protein kinase A. Inhibitor kinetics suggest that protein kinase A signaling triggers excystation, whereas calcium signaling is mainly required later, for parasite activation and emergence.

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“…Unfortunately, the knowledge of the transport machinery in Giardia is limited, mostly due to the fact that trophozoites lack essential secretory organelles, such as morphologically identifiable Golgi apparatus and secretory granules (4,5). However, constitutive protein secretion in Giardia is exemplified by the continuous transport to the plasma membrane and release into the culture medium of variant-specific surface proteins (VSP) (6,7), whereas regulated secretion apparently occurs only during encystation (3,8). The biogenesis of the Golgi complex and of typical secretory granules containing cyst wall materials, called encystationspecific secretory vesicles (ESVs), has been reported to occur at early stages of trophozoite differentiation into cyst (8 -10).…”

mentioning

confidence: 99%

“…Since Giardia derives from the earliest branch of the eukaryotic line of descent (17), the study of the biogenesis of secretory organelles that occurs during differentiation might provide new insights into the minimal machinery required for protein transport by the regulated secretory pathway in eukaryotes (1)(2)(3). Moreover, the ability to control the biogenesis of the Golgi apparatus (5) and secretory granules (8) in Giardia by just varying the composition of the culture medium (18) offers an excellent opportunity to investigate the physiological mechanisms underlying granule formation, maturation, and discharge (1,2).…”

mentioning

confidence: 99%

Identification and Characterization of a Novel Secretory Granule Calcium-binding Protein from the Early Branching Eukaryote Giardia lamblia

Touz¹,

Gottig²,

Nash³

et al. 2002

Journal of Biological Chemistry

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Giardia lamblia is a flagellate protozoan that infects humans and other mammals and the most frequently isolated intestinal parasite worldwide. Giardia trophozoites undergo essential biological changes to survive outside the intestine of their host by differentiating into infective cysts. Cyst formation, or encystation, is considered one of the most primitive adaptive responses developed by eukaryotes early in evolution and crucial for the transmission of the parasite among susceptible hosts. During this process, proteins that will assemble into the extracellular cyst wall (CWP1 and CWP2) are transported to the cell surface within encystation-specific secretory vesicles (ESVs) by a developmentally regulated secretory pathway. Cyst wall proteins (CWPs) are maintained as a dense material inside the ESVs, but after exocytosis, they form the fibrillar matrix of the cyst wall. Little is known about the molecular mechanisms involved in granule biogenesis and discharge in Giardia, as well as the assembly of the extracellular wall. In this work, we provide evidences that a novel 54-kDa protein that exclusively localizes to the ESVs is induced during encystation similar to CWPs, proteolytically processed during granule maturation, and able to bind calcium in vitro. The gene encoding this molecule predicts a novel protein (called gGSP for G. lamblia Granule-specific Protein) without homology to any other protein reported in public databases. Nevertheless, it possesses characteristics of calcium-sequestering molecules of higher eukaryotes. Inhibition of gGSP expression abolishes cyst wall formation, suggesting that this secretory granule protein regulates Ca 2؉

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Giardia lamblia: Regulation of secretory vesicle formation and loss of ability to reattach during encystation in vitro

Cited by 50 publications

References 24 publications

Cyst wall synthase: N-acetylgalactosaminyltransferase activity is induced to form the novel N-acetylgalactosamine polysaccharide in the Giardia cyst wall

Cyst wall synthase: N-acetylgalactosaminyltransferase activity is induced to form the novel N-acetylgalactosamine polysaccharide in the Giardia cyst wall

Calcium Signaling in Excystation of the Early Diverging Eukaryote, Giardia lamblia

Identification and Characterization of a Novel Secretory Granule Calcium-binding Protein from the Early Branching Eukaryote Giardia lamblia

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