Abstract
Entamoeba histolytica is the etiologic agent of human amoebiasis, disease that causes 40,000 to 100,000 deaths annually worldwide. The cytopathic activity as well as the growth and differentiation of this microorganism is dependent on both, extracellular and free cytoplasmic calcium. However, few is known about the proteins that regulate the calcium flux in this parasite. In many cells, the calcium extrusion from the cytosol is performed by plasma membrane Ca2+-ATPases and calcium/cation exchangers. The aim of this work was to identify a calcium/cation exchanger of E. histolytica and to analyze its possible role in some cellular processes triggered by calcium flux, such as the programmed cell death and in vitro virulence. By searching putative calcium/cation exchangers in the genome database of E. histolyica we identified a protein belonging to the CCX family (EhCCX). We generated a specific antibody against EhCCX, which showed that this protein was expressed in higher levels in E. histolytica than its orthologous in the non-pathogenic amoeba E. dispar. In addition, the expression of EhCCX was increased in trophozoites incubated with hydrogen peroxide. This E. histolytica exchanger was localized in the plasma membrane and in the membrane of some cytoplasmic vesicles. However, after 10 min of erythrophagocytosis, EhCCX was found predominantly in the plasma membrane of the trophozoites. On the other hand, the parasites that overexpress this exchanger contained higher cytosolic calcium levels than control, but the extrusion of calcium after the addition of hydrogen peroxide was more efficient in EhCCX-overexpressing trophozoites; consequently, the programmed cell death was retarded in these parasites. Interestingly, the overexpression of EhCCX increased the in vitro virulence of trophozoites. These results suggest that EhCCX plays important roles in the programmed cell death and in the in vitro virulence of E. histolytica.
Highlights
The ion calcium (Ca2+) is a highly versatile secondary messenger that operates over a wide temporal range to regulate many different cellular processes (Berridge et al, 2003)
The superfamily of calcium exchangers comprises five branches (Lytton, 2007; Emery et al, 2012): (i) H+/ Ca2+ exchangers (CAX), mainly found in plants; (ii) bacteria exchangers (YRGB); (iii) Na+/Ca2+ exchangers (NCX or SLC8); (iv) Na+/Ca2+ + K+ exchangers (NCKX or SLC24); and (v) Ca2+/cation exchangers (CCX), which contains one mammalian member, the Na+/Ca2+ or Li+ exchanger (NCLX) that is named as NCKX6
The overexpression of EhCCX retarded the programmed cell death and increased the in vitro virulence. These results suggest that the Ca2+ flux through EhCCX plays an important role in the programmed cell death and the virulence of E. histolytica
Summary
The ion calcium (Ca2+) is a highly versatile secondary messenger that operates over a wide temporal range to regulate many different cellular processes (Berridge et al, 2003). In many cells Ca2+ extrusion from the cytosol is performed by plasma membrane Ca2+-ATPases (PMCAs) and by Ca2+/cations exchangers (Berridge et al, 2003). PMCAs are involved in the maintenance of the resting cytoplasmic concentration of Ca2+, whereas exchangers are important in the restoration of cytoplasmic concentration of Ca2+ after it has been elevated during signaling (Harper and Sage, 2016). Exchangers participate in the entry of Ca2+ to cytoplasm, since they can reverse its transport in response to changes in the concentration of the transported ions and membrane potential (Harper and Sage, 2016). The superfamily of calcium exchangers comprises five branches (Lytton, 2007; Emery et al, 2012): (i) H+/ Ca2+ exchangers (CAX), mainly found in plants; (ii) bacteria exchangers (YRGB); (iii) Na+/Ca2+ exchangers (NCX or SLC8); (iv) Na+/Ca2+ + K+ exchangers (NCKX or SLC24); and (v) Ca2+/cation exchangers (CCX), which contains one mammalian member, the Na+/Ca2+ or Li+ exchanger (NCLX) that is named as NCKX6
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
