Entamoeba histolytica: Cell cycle and nuclear division

Orozco, Esther; Solis, Francisco J.; Domínguez, Jorge Domínguez; Chávez, Benigno Zenteno; Hernández, Fidel de la Cruz Hernández

doi:10.1016/0014-4894(88)90011-2

Cited by 57 publications

(38 citation statements)

References 10 publications

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“…In addition to their association with actin assemblies, mammalian Diaphanous proteins mDia1 and mDia3 associate with spindle microtubular assemblies to regulate spindle positioning and proper chromosome alignment to the kinetochore (26,67). In E. histolytica, microtubular assemblies have been found to be both radial (13,41,57) and bipolar spindles (13). Practically nothing is known about the mode of chromosome alignment or segregation on the radial or bipolar assembly in E. histolytica.…”

Section: Resultsmentioning

confidence: 99%

Entamoeba histolytica Encodes Unique Formins, a Subset of Which Regulates DNA Content and Cell Division

Majumder

Lohia

2008

Infect Immun

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The formin family of proteins mediates dynamic changes in actin assembly in eukaryotes, and therefore it is important to understand the function of these proteins in Entamoeba histolytica, where actin forms the major cytoskeletal network. In this study we have identified the formin homologs encoded in the E. histolytica genome based on sequence analysis. Using multiple tools, we have analyzed the primary sequences of the eight E. histolytica formins and discovered three subsets: (i) E. histolytica formin-1 to -3 (Ehformin-1 to -3), (ii) Ehformin-4, and (iii) Ehformin-5 to -8. Two of these subsets (Ehformin-1 to -3 and Ehformin-4) showed significant sequence differences from their closest homologs, while Ehformin-5 to -8 were unique among all known formins. Since Ehformin-1 to -3 showed important sequence differences from Diaphanous-related formins (DRFs), we have studied the functions of Ehformin-1 and -2 in E. histolytica transformants. Like other DRFs, Ehformin-1 and -2 associated with F-actin in response to serum factors, in pseudopodia, in pinocytic and phagocytic vesicles, and at cell division sites. Ehformin-1 and -2 also localized with the microtubular assembly in the nucleus, indicating their involvement in genome segregation. While increased expression of Ehformin-1 and -2 did not affect phagocytosis or motility, it clearly showed an increase in the number of binucleated cells, the number of nuclei in multinucleated cells, and the average DNA content of each nucleus, suggesting that these proteins regulate both mitosis and cytokinesis in E. histolytica.Polymerization of actin into helical filaments is nucleated by different groups of actin-binding proteins, which in turn are controlled by specific signaling molecules in eukaryotic cells (10, 66). Currently, the three known groups of F-actin nucleating factors are the Arp2/3 complex, formins, and spire (10, 21). Formin homology proteins promote rapid assembly of unbranched actin filaments and local reorganization of higherorder cellular structures to execute specified cytoskeletal functions (reviewed in reference 21). These multidomain proteins have many isoforms that are ubiquitously expressed and perform diverse cellular functions in almost all eukaryotic cells, from vertebrates and plants to unicellular protists (25). The defining feature of formin proteins is the formin homology 2 (FH2) domain, which is required for the nucleation and elongation of nascent actin filaments (24,43,46). The FH1 domain, preceding the FH2 domain, is another key region found in most formins and is made up of tandem repeats of proline and other amino acids (24). Polyproline residues in the FH1 domain interact with profilin to recruit assembly-competent actin monomers in the vicinity of the FH2 domain (50, 52, 61). The FH1 domain also interacts with Src homology 3 (SH3) domainor WW domain-containing proteins (17, 59). Thus, the core FH1-FH2 region nucleates unbranched actin filaments, unlike the Arp2/3 complex, which creates branched filaments (21). Other regulatory domains,...

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Section: Resultsmentioning

confidence: 99%

Entamoeba histolytica Encodes Unique Formins, a Subset of Which Regulates DNA Content and Cell Division

Majumder

Lohia

2008

Infect Immun

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“…Since Entamoeba at rest lack cytoplasmic microtubules, which appear only in the nuclei of dividing cells (Orozco et al 1988), the target of oryzalin may be restricted to microtubules that appear as mitotic spindles during nuclear division. Thus, the aforementioned ®ndings suggest that oryzalin inhibits encystation through the inhibition of nuclear division.…”

Section: Discussionmentioning

confidence: 99%

“…Accumulation of trophozoites in the mitotic phase during culture with oryzalin Since Entamoeba at rest lack cytoplasmic mictotubules and the latter appear only in the nuclei during nuclear division (Orozco et al 1988), we examined the nuclei of trophozoites incubated in growth medium supplemented with oryzalin by light microscopy. As shown in Fig.…”

Section: Eect Of Pretreatment With Oryzalin On Encystationmentioning

confidence: 99%

Effect of the antitubulin drug oryzalin on the encystation of Entamoeba invadens

Makioka¹,

Kumagai²,

Ohtomo³

et al. 2000

Parasitol Res

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We have recently demonstrated that the antimicrotubule drug oryzalin inhibits the growth of Entamoeba invadens as well as E. histolytica, the former being more resistant to the drug than the latter, and that effective doses of oryzalin are higher for Entamoeba than for the other parasitic protozoa examined thus far. The aim of the present study was to examine the effect of oryzalin on the encystation of E. invadens using an axenic encystation system in vitro. Oryzalin inhibited the encystation of E. invadens strain IP-1 in a dose-dependent manner. The addition of oryzalin after the induction of encystation was also inhibitory for encystation and cyst maturation. Trophozoites incubated for 1 day in encystation medium with oryzalin did not encyst after removal of the drug. Although trophozoites grown in the presence of 300 microM oryzalin for 2 days did not encyst after their transfer to encystation medium containing the same concentration of drug, a number of trophozoites survived for at least 3 days. In contrast, trophozoites grown in the absence of oryzalin neither survived nor encysted after their transfer to encystation medium supplemented with the drug, which suggests that pretreatment of trophozoites with oryzalin contributes to their continued survival as trophozoites, i.e., without their transforming into cysts, in encystation medium. Trophozoites grown with oryzalin did encyst after their transfer to encystation medium without the drug. Accumulation of trophozoites in the mitotic phase was observed after culture with oryzalin. When cysts prepared at day 1 of encystation, most of which were mononucleate, were reincubated in the presence of oryzalin for an additional 2 days, inhibition of their maturation was observed. Thus, oryzalin is a potent mitotic-phase inhibitor of E. invadens and may become a useful tool for studies on the relationship between the cell cycle and encystation of this parasite.

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“…To interprete these results on a single-cell basis, it is important to synchronize cell cultures prior to making measurements and a few attempts have been made in the past to synchronize E. histolytica cultures by using serum deprivation or cytostatic drugs (Orozco et al 1988).…”

Section: Discussionmentioning

confidence: 99%

“…Our attempts to synchronize E. histolytica with colchicine (600 lg/ml) as reported by Orozco et al (1988) were unsuccessful: even after 12 h of drug treatment, the culture was not synchronized (data not shown). Even Orozco et al (1988) reported only one synchronous cycle with a clone of HM1:1MSS, i.e., clone L-6, and not with the parent strain which we have employed.…”

Section: Discussionmentioning

confidence: 99%

Role of serum in regulating the Entamoeba histolytica cell cycle: a flowcytometric analysis

Vohra

Mahajan

Ganguly

1998

Parasitology Research

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To identify stage-specific molecules that might be important in pathogenicity, we focused on synchronizing Entamoeba histolytica HM1:1MSS axenic cultures by serum deprivation. By growing trophozoites in medium containing 2% serum for 16 h and then replacing with complete medium, we found that most of the trophozoites were in the G0/G1 phase of the cell cycle. Subsequently, the distribution of trophozoites in G0/G1, S and G2/M phases was studied for up to 24 h and it was observed that after 8 h, the trophozoites began to come out of the quiescent G0/G1 phase and the S and G2/M populations increased, indicating that certain serum factors regulate induction of cell division. It will be important to investigate these factors to find serum substitutes for cultivation media.

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Entamoeba histolytica: Cell cycle and nuclear division

Cited by 57 publications

References 10 publications

Entamoeba histolytica Encodes Unique Formins, a Subset of Which Regulates DNA Content and Cell Division

Entamoeba histolytica Encodes Unique Formins, a Subset of Which Regulates DNA Content and Cell Division

Effect of the antitubulin drug oryzalin on the encystation of Entamoeba invadens

Role of serum in regulating the Entamoeba histolytica cell cycle: a flowcytometric analysis

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