Entamoeba histolytica: Comparison of the role of receptors and filamentous actin among various endocytic processes

Welter, Brenda H.; Powell, Rhonda R.; Laughlin, Richard; McGugan, Glen C.; Bonner, Mark; King, Ada; Temesvari, Lesly A.

doi:10.1016/j.exppara.2005.12.012

Cited by 14 publications

(12 citation statements)

References 47 publications

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“…However, when the endocytic process was followed using higher holoTf concentrations, it was also Tfbp-independent. This result is in agreement with Welter et al (2006), who did not obtain saturation when using concentrations of holoTf in the micromolar range.…”

Section: Discussionsupporting

confidence: 81%

“…This result together with that of the wortmannin experiment suggests that holoTf mainly enters via the clathrin route and relies to a lesser extent on other mechanisms. Recently, it was reported that holoTf could be internalized by fluid-phase endocytocis in E. histolytica (Welter et al, 2006). Similarly, in rat hepatocytes, it was found that holoTf is endocytosed by two pathways (Qian & Tang, 1995;Richardson & Ponka, 1997).…”

Section: Discussionmentioning

confidence: 98%

“…This mAb co-localized with FITC-holoTf on the amoeba membrane and also in the cytoplasm, as observed by confocal laser-scanning microscopy (Reyes-Ló pez et al , 2001). In this work we suggest that E. histolytica possesses at least two ways to internalize holoTf: one via a specific binding protein, EhTfbp, reported here, and another via a receptor-independent process (Welter et al, 2006). It is suggested that, due to its absolute requirement for the ion, the parasite must obtain iron through multiple mechanisms.…”

mentioning

confidence: 95%

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Acetaldehyde/alcohol dehydrogenase-2 (EhADH2) and clathrin are involved in internalization of human transferrin by Entamoeba histolytica

et al. 2011

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Transferrin (Tf) is a host glycoprotein capable of binding two ferric-iron ions to become holotransferrin (holoTf), which transports iron in to all cells. Entamoeba histolytica is a parasitic protozoan able to use holoTf as a sole iron source in vitro. The mechanism by which this parasite scavenges iron from holoTf is unknown. An E. histolytica holoTf-binding protein (EhTfbp) was purified by using an anti-human transferrin receptor (TfR) monoclonal antibody. EhTfbp was identified by MS/MS analysis and database searches as E. histolytica acetaldehyde/alcohol dehydrogenase-2 (EhADH2), an iron-dependent enzyme. Both EhTfbp and EhADH2 bound holoTf and were recognized by the anti-human TfR antibody, indicating that they correspond to the same protein. It was found that the amoebae internalized holoTf through clathrin-coated pits, suggesting that holoTf endocytosis could be important for the parasite during colonization and invasion of the intestinal mucosa and liver. INTRODUCTIONIron is a vital element for nearly all living organisms but it is bound to proteins to prevent tissue damage by oxygen free-radical formation. In mammals, iron is an enzyme cofactor and forms part of haemoproteins. In addition, iron is sequestered by proteins such as the iron-transporter transferrin (Tf) in serum and the iron-withholding defence lactoferrin (Lf) in mucosae. Thus, the free ionic-iron concentration (~10 218 M) is far too low to sustain the growth of pathogens (Bullen et al., 1978).Bacterial pathogens have developed several mechanisms for obtaining host iron; one of these is the use of receptors that can bind iron-containing proteins, such as holoTf, holoLf, and haemoglobin, with very high host specificity (Weinberg, 2009). In Gram-negative bacteria, receptors for holoTf generally consist of two iron-regulated outer-membrane proteins, termed TbpA and TbpB (Genco & Desai, 1996), and iron is removed from its receptor in an energydependent process. A transferrin-binding protein A (StbA, also known as IsdA), has been reported in Staphylococcus aureus strain RN6390 (Maresso & Schneewind, 2006;Mazmanian et al., 2003;Taylor & Heinrichs, 2002). Homologues of the isd gene are also found in Gram-positive bacilli (Bierne et al., 2004; Gat et al., 2008;Maresso & Schneewind, 2006). These pathogens have several elaborate mechanisms for iron sequestration.Furthermore, it has been reported that S. aureus strain BB and Staphylococcus epidermidis strain 138 utilize the enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (Gap or Tpn) to bind holoTf (Modun & Williams, 1999). Interestingly, the parasite Trypanosoma brucei also makes use of GAPDH for holoLf binding rather than for holoTf binding (Tanaka et al., 2004). Enzymes that bind holoTf have not previously been described in parasitic protozoa.Iron uptake in mammalian cells is initiated by the binding of holoTf to the TfR on the cell surface. Then, via clathrincoated pits, the Tf-TfR complex becomes trapped within endocytic vesicles, which are rapidly acidified, and the iron is removed from ...

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Section: Discussionsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 98%

mentioning

confidence: 95%

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Acetaldehyde/alcohol dehydrogenase-2 (EhADH2) and clathrin are involved in internalization of human transferrin by Entamoeba histolytica

et al. 2011

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“…However, when the endocytic process was followed using high TF concentrations, the TF was internalized independently of the binding protein [Reyes-López et al, 2011]. This result is in agreement with the observation that TF internalization is unsaturable [Welter et al, 2006]. The presence of clathrin has been demonstrated in some protozoa and in E. histolytica [León-Sicairos et al, 2005;López-Soto et al, 2009a;Reyes-López et al, 2011]; clathrin may be important in parasites for the acquisition of nutrients.…”

Section: E Histolytica Transferrin Binding Proteins Ehtfbpssupporting

confidence: 80%

“…Interestingly, this parasite has two methods of obtaining iron from TF: one is mediated by receptor-independent internalization [Welter et al, 2006] and the other is through three specific TF-binding proteins (EhTFbps) of 70, 96 and 140 kDa of molecular mass, identified by overlay assays with holoTF. The 140 kDa protein is recognized by an anti-HsTFR mAb B3/25 (Boehringerheim cat.…”

Section: E Histolytica Transferrin Binding Proteins Ehtfbpsmentioning

confidence: 99%