Primary structure of Entamoeba histolytica γ-tubulin and localisation of amoebic microtubule organising centres

Ray, Sib Sankar; Gangopadhyay, Samudra S.; Pande, Gopal; Samuelson, John; Lohia, Anuradha

doi:10.1016/s0166-6851(97)00157-6

Cited by 17 publications

(4 citation statements)

References 12 publications

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“…It has also been predicted that the microtubular assembly may be unstable due to steric hindrances in tubulin polymerization. However, reasons for the formation of a radial microtubular assembly instead of a typical bipolar spindle are not clear because proteins required for spindle pole or MTOC formation are present in E. histolytica (Ray et al ., 1997). It has been difficult to study microtubule dynamics and chromosome segregation in E. histolytica because little is known about proteins regulating microtubular assembly .…”

Section: Introductionmentioning

confidence: 99%

Eh Klp5 is a divergent member of the kinesin 5 family that regulates genome content and microtubular assembly in Entamoeba histolytica

Dastidar

Majumder

Lohia³

2007

Cell Microbiol

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SummaryEarlier studies have established two unusual features in the cell division cycle of Entamoeba histolytica. First, microtubules form a radial assembly instead of a bipolar mitotic spindle, and second, the genome content of E. histolytica cells varied from 1¥ to 6¥ or more. In this study, Eh Klp5 was identified as a divergent member of the BimC kinesin family that is known to regulate formation and stabilization of the mitotic spindle in other eukaryotes. In contrast to earlier studies, we show here that bipolar microtubular spindles were formed in E. histolytica but were visible only in 8-12% of the cells after treatment with taxol. The number of bipolar spindles was significantly increased in Eh Klp5 stable transformants (20-25%) whereas Eh Klp5 double-stranded RNA (dsRNA) transformants did not show any spindles (< 1%). The genome content of Eh Klp5 stable transformants was regulated between 1¥ and 2¥ unlike control cells. Binucleated cells accumulated in Eh Klp5 dsRNA transformants and after inhibition of Eh Klp5 with small molecule inhibitors in control cells, suggesting that cytokinesis was delayed in the absence of Eh Klp5. Taken together, our results indicate that Eh Klp5 regulates microtubular assembly, genome content and cell division in E. histolytica. Additionally, Eh Klp5 showed alterations in its drug-binding site compared with its human homologue, Hs Eg5 and this was reflected in its reduced sensitivity to Eg5 inhibitors -monastrol and HR22C16 analogues.

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Section: Introductionmentioning

confidence: 99%

Eh Klp5 is a divergent member of the kinesin 5 family that regulates genome content and microtubular assembly in Entamoeba histolytica

Dastidar

Majumder

Lohia³

2007

Cell Microbiol

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“…Later we reported microtubules in the cytoplasm of trophozoites activated by collagen type I and Ca 2ϩ . It is very interesting to note that tubulin from this parasite is one of the most divergent tubulins, which probably makes it insensitive to known microtubuletargeted drugs [Katiyar and Edlind, 1996;Ray et al, 1997] and causes it to have atypical futures. For example, its detection in cytoplasm has been difficult and it is interesting to note the lack of centrosome-like structures and the use of an apparently rudimentary spindle that does not form a metaphase stage [Ray et al, 1997].…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, transmission electron microscopy of microtubules that were detected exclusively in the nucleus [Orozco et al, 1988] were recently detected in the cytoplasm of trophozoites activated by collagen type I and Ca 2ϩ . Interestingly, a very recent report showed microtubule organizing centers (MTOCs) using specific antibodies against ␥-tubulin [Ray et al, 1997]. In an effort to define this event, we study the distribution of cytoskeleton microfilaments, microtubules, IF and integrin distribution in trophozoites activated by collagen type I and Ca 2ϩ .…”

Section: Introductionmentioning

confidence: 97%

Entamoeba histolytica trophozoites activated by collagen type I and Ca²⁺ have a structured cytoskeleton during collagenase secretion

Muñoz

Das

Tovar

2001

Cell Motil. Cytoskeleton

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A peculiar characteristic of Entamoeba histolytica trophozoites is their capacity to invade human tissues. One of the cellular determinants of invasion may include adhesion to extracellular matrix components such as collagen, induction, and secretion of electron-dense granules (EDG) and tissue digestion. The mechanism and receptors involved in this process are not well understood. Previous results suggested that cytoskeleton plays a very important role during EDG secretion. We present evidence suggesting that adhesion to collagen and activation of EDG secretion are integrin-dependent events, since beta1 subunits detected by antibodies are concentrated at membrane sites where collagen and actin were colocalized. Furthermore, the involvement of actin, vimentin, and tubulin in restructuring cytoskeleton during EDG secretion was evident, since cytoskeleton isolation was possible exclusively in activated cells. Studies of immunolocalization of tubulin, actin, and vimentin by immunofluorescence and transmission electron microscopy suggest a role for cytoskeleton in EDG secretion.

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“…Bipolar spindle assemblies are nucleated at microtubule organizing centers (MTOCs). In spite of the presence of the components of microtubule organizing centers (MTOCs)-such as c-tubulin in E. histolytica (Ray et al 1997, Vayssie et al 2004, bipolar spindle assembly could not be visualized in normally cycling cells. However, after incubation with taxol-a microtubule stabilizing drug, bipolar spindles were observed at low frequency (8-12%) (Dastidar et al 2007).…”

Section: Alterations In the Microtubular Assembly May Lead To Erraticmentioning

confidence: 99%

Genome Re-duplication and Irregular Segregation Occur During the Cell Cycle of Entamoeba histolytica

et al. 2007

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Heterogeneity of genome content is commonly observed in axenic cultures of Entamoeba histolytica. Cells with multiple nuclei and nuclei with heterogenous genome contents suggest that regulatory mechanisms that ensure alternation of DNA synthesis and mitosis are absent in this organism. Therefore, several endo-reduplicative cycles may occur without mitosis. The data also shows that unlike other endo-reduplicating organisms, E.histolytica does not undergo a precise number of endo-reduplicative cycles. We propose that irregular endo-reduplication and genome partitioning lead to heterogeneity in the genome content of E.histolytica trophozoites in their proliferative phase. The goal of future studies should be aimed at understanding the mechanisms that are involved in (a) accumulation of multiple genome contents in a single nucleus; (b) genome segregation in nuclei that contain multiple genome contents and (c) maintenance of genome fidelity in E. histolytica.

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Primary structure of Entamoeba histolytica γ-tubulin and localisation of amoebic microtubule organising centres

Cited by 17 publications

References 12 publications

Eh Klp5 is a divergent member of the kinesin 5 family that regulates genome content and microtubular assembly in Entamoeba histolytica

Eh Klp5 is a divergent member of the kinesin 5 family that regulates genome content and microtubular assembly in Entamoeba histolytica

Entamoeba histolytica trophozoites activated by collagen type I and Ca²⁺ have a structured cytoskeleton during collagenase secretion

Genome Re-duplication and Irregular Segregation Occur During the Cell Cycle of Entamoeba histolytica

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Primary structure of Entamoeba histolytica γ-tubulin and localisation of amoebic microtubule organising centres

Cited by 17 publications

References 12 publications

Eh Klp5 is a divergent member of the kinesin 5 family that regulates genome content and microtubular assembly in Entamoeba histolytica

Eh Klp5 is a divergent member of the kinesin 5 family that regulates genome content and microtubular assembly in Entamoeba histolytica

Entamoeba histolytica trophozoites activated by collagen type I and Ca2+ have a structured cytoskeleton during collagenase secretion

Genome Re-duplication and Irregular Segregation Occur During the Cell Cycle of Entamoeba histolytica

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Entamoeba histolytica trophozoites activated by collagen type I and Ca²⁺ have a structured cytoskeleton during collagenase secretion