Trophozoites of<i>Giardia lamblia</i>may have a Golgi-like structure

Lanfredi-Rangel, Adriana; Kattenbach, W. M.; Diniz, José A.; Souza, Wanderley de

doi:10.1111/j.1574-6968.1999.tb08851.x

Cited by 30 publications

(4 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The diplomonads as the most basal eukaryotes known to date may shed light on some of these developments. For example, certain groups suggested that Giardia has no membrane structures resembling a Golgi apparatus, whereas others have claimed to detect the classical multicisternal membrane arrangement in EM studies (25,43). In agreement with the former, we recently showed that sorting of cargo proteins to the regulated ESV or the constitutive VSP pathways occurred at or immediately after export from the ER during encystation (18).…”

Section: Discussionsupporting

confidence: 71%

“…In a tEM survey using a novel method for preparing adhering Giardia for analysis we found no evidence for conventional Golgi stacks in a single parasite. Most encysting cells contained a large spindle-shaped membrane structure (up to 2 m) adjacent to one or both nuclei that had been interpreted as Golgi stacks in earlier EM investigations of randomly sectioned cells (43), but resembled "karmellae" from higher eukaryotes (i.e. layers of proliferated ER membranes wrapped around the nucleus (44)).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

An Ancestral Secretory Apparatus in the Protozoan Parasite Giardia intestinalis

Marti

Regös

et al. 2003

Journal of Biological Chemistry

104

137

View full text Add to dashboard Cite

The protozoan parasite Giardia intestinalis belongs to one of the earliest diverged eukaryotic lineages. This is also reflected in a simple intracellular organization, as Giardia lacks common subcellular compartments such as mitochondria, peroxisomes, and apparently also a Golgi apparatus. During encystation, developmentally regulated formation of large secretory compartments containing cyst wall material occurs. Despite the lack of any morphological similarities, these encystation-specific vesicles (ESVs) show several biochemical characteristics of maturing Golgi cisternae. Previous studies suggested that Golgi structure and function are induced only during encystation in Giardia, giving rise to the hypothesis that ESVs, as a Giardia Golgi equivalent, are generated de novo. Alternatively, ESV compartments could be built on the template structure of a cryptic Golgi in trophozoites in response to ER export of cyst wall material during encystation. We addressed this question by defining the molecular framework of the Giardia secretory apparatus using a comparative genomic approach. Analysis of the corresponding transcriptome during growth and encystation revealed surprisingly little stage-specific regulation. A panel of antibodies was generated against selected marker proteins to investigate the developmental dynamics of the endomembrane system. We show evidence that Giardia accommodates the export of large amounts of cyst wall material through re-organization of membrane compartment(s) in trophozoites with biochemical similarities to ESVs. This suggests that ESVs are selectively stabilized Golgi-like compartments in a unique and archetypical secretory system, which arise from a structural template in trophozoites rather than being generated de novo.

show abstract

Section: Discussionsupporting

confidence: 71%

Section: Discussionmentioning

confidence: 99%

An Ancestral Secretory Apparatus in the Protozoan Parasite Giardia intestinalis

Marti

Regös

et al. 2003

Journal of Biological Chemistry

104

137

View full text Add to dashboard Cite

show abstract

“…Possibly in these cases, the CWP2 basic extension competes with endogenous CWP2 for an anionic receptor. Localization of T CWP2 -HA and VSPH7(ϪTMϩT CWP2 )-HA moved from the ER to a more limited clamp-shaped pattern adjacent to the ER/nuclear envelope compartment, in a pattern similar to the Golgispecific marker 12-(N-methyl-N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl))-ceramide (3,41). In these experiments, the presence of the basic extension inhibited extracellular secretion of chimeras containing the CWP2 basic extension.…”

Section: Discussionmentioning

confidence: 97%

Active and Passive Mechanisms Drive Secretory Granule Biogenesis during Differentiation of the Intestinal Parasite Giardia lamblia

Gottig

Elias

Quiroga

et al. 2006

Journal of Biological Chemistry

View full text Add to dashboard Cite

The parasitic protozoan Giardia lamblia undergoes important changes to survive outside the intestine of its host by differentiating into infective cysts. During encystation, three cyst wall proteins (CWPs) are specifically expressed and concentrated within encystation-specific secretory vesicles (ESVs). ESVs are electron-dense secretory granules that transport CWPs before exocytosis and extracellular polymerization into a rigid cyst wall. Because secretory granules form at the trans-Golgi in higher eukaryotes and because Giardia lacks an identifiable Golgi apparatus, the aim of this work was to investigate the molecular basis of secretory granule formation in Giardia by examining the role of CWPs in this process. Although CWP1, CWP2, and CWP3 are structurally similar in their 26-kDa leucine-rich overlapping region, CWP2 is distinguished by the presence of a 13-kDa C-terminal basic extension. In non-encysting trophozoites, expression of different CWP chimeras showed that the CWP2 basic extension is necessary for biogenesis of ESVs, which occurs in a compartment derived from the endoplasmic reticulum. Nevertheless, the CWP2 basic extension per se is insufficient to trigger ESV formation, indicating that other domains in CWPs are also required. We found that CWP2 is a key regulator of ESV formation by acting as an aggregation factor for CWP1 and CWP3 through interactions mediated by its conserved region. CWP2 also acts as a ligand for sorting via its C-terminal basic extension. These findings show that granule biogenesis requires complex interactions among granule components and membrane receptors.

show abstract

“…As the majority of ceramide is taken up from the culture medium or from the small intestinal milieu, some could be generated by breaking down sphingomyelin by Smase enzymes [38•, 45–47]. Exogenously administered fluorescently conjugated ceramide was found to be targeted in the ER/perinuclear regions of trophozoites [48, 49], and in encysting cells it reacted with parallel perinuclear cisternae, which appeared to be a Golgi apparatus [25, 35, 36, 50]. This suggests that exogenous ceramide not only serves as a precursor of GlcCer but is also required for organelle biogenesis in Giardia.…”

Section: Sphingolipids and Encystationmentioning

confidence: 99%

Sphingolipids, Lipid Rafts, and Giardial Encystation: The Show Must Go On

et al. 2015

View full text Add to dashboard Cite

Sphingolipids are sphingosine-based phospholipids, which are present in the plasma and endomembranes of many eukaryotic cells. These lipids are involved in various cellular functions, including cell growth, differentiation, and apoptosis. In addition, sphingolipid and cholesterol-enriched membrane microdomains (also called “lipid rafts”) contain a set of proteins and lipids, which take part in the signaling process in response to intra- or extracellular stimuli. Recent findings suggest that sphingolipids, especially glucosylceramide, play a critical role in inducing encystation and maintaining the cyst viability in Giardia. Similarly, the assembly/disassembly of lipid rafts modulates the encystation and cyst production of this ubiquitous enteric parasite. In this review article, we discuss the overall progress in the field and examine whether sphingolipids and lipid rafts can be used as novel targets for designing therapies to control infection by Giardia, which is rampant in developing countries, where children are especially vulnerable.

show abstract

Trophozoites ofGiardia lambliamay have a Golgi-like structure

Cited by 30 publications

References 27 publications

An Ancestral Secretory Apparatus in the Protozoan Parasite Giardia intestinalis

An Ancestral Secretory Apparatus in the Protozoan Parasite Giardia intestinalis

Active and Passive Mechanisms Drive Secretory Granule Biogenesis during Differentiation of the Intestinal Parasite Giardia lamblia

Sphingolipids, Lipid Rafts, and Giardial Encystation: The Show Must Go On

Contact Info

Product

Resources

About