Ubiquitin-like Atg8 protein is expressed during autophagy and the encystation process in Naegleria gruberi

Abstract

Members of the Naegleria genus are free-living amoebae, and the only pathogenic specie described to date for humans is N. fowleri. However, as the complete genome of this specie has not been reported, non-pathogenic N. gruberi is employed to describe molecular pathways in N. fowleri. Regardless, certain mechanisms, such as autophagy, have not yet been characterized in N. gruberi. Autophagy is involved in different cellular processes in some protozoa, including the recycling of unnecessary organelles, development, and cell differentiation. In this work, we characterized autophagy in N. gruberi using the specific inducer rapamycin. The formation of autophagy vacuoles in treated trophozoites was observed by ultrastructural analysis, and real time quantitative PCR demonstrated overexpression of the atg8 gene. In addition, we detected an increase in the vacuolar acidification of treated amoebae using the LysoTracker. Finally, confocal microscopy was utilized to identify Atg8 protein signal in the cytoplasm of N. gruberi trophozoites induced with rapamycin and even in trophozoites induced to encyst. In conclusion, N. gruberi possesses an Atg8 protein homolog that is overexpressed during the autophagic mechanism induced by rapamycin and also during encystation of this free-living amoeba.

Biogenesis of Autophagosome in Trichomonas vaginalis during Macroautophagy Induced by Rapamycin‐treatment and Iron or Glucose Starvation Conditions

“…) and encystation in Naegleria gruberi (Cárdenas‐Zúñiga et al. ). In humans, it is related to tumorigenesis, neurodegenerative diseases, type II diabetes, and longevity (Mizushima et al.…”

Autophagy-related Djatg8 is required for remodeling in planarians Dugesia japonica

“…From yeast to mammals, autophagy is an important mechanism for sustaining cellular homeostasis through facilitating the degradation and recycling of aged and cytotoxic components (Yoshimori and Noda, 2008; Kourtis and Tavernarakis, 2009; Xie et al, 2008; Cárdenas-Zuñiga et al, 2016). In yeast, autophagy initiation, cargo recognition, cargo engulfment and vesicle closure is Atg8-dependent (Yoshimori and Noda, 2008; Kourtis and Tavernarakis, 2009; Xie et al, 2008; Cárdenas-Zuñiga et al, 2016). In mammals, Atg8 belongs to the LC3/GABARAP protein family, which consists of seven family proteins [LC3A (two splice variants), LC3B, LC3C, GABARAP, GABARAPL1 and GABARAPL2] (Marco et al, 2016).…”

“…Autophagy was first found in yeasts wherein more than 30 autophagy-related genes have been identified ( Atg1 – Atg32 ). The majority of these Atg genes are also found in higher eukaryotes, including mammals (Yoshimori and Noda, 2008; Kourtis and Tavernarakis, 2009; Xie et al, 2008; Cárdenas-Zuñiga et al, 2016). The Atg8 protein has been explored as one of the most important Atg molecules in autophagy; it is a ubiquitin-like protein involved in the labeling of autophagic vesicles (AVs), and actively controls their formations (Cárdenas-Zuñiga et al, 2016; Krick and Thumm, 2016).…”

A Novel Cysteine Protease Inhibitor of Naegleria fowleri That Is Specifically Expressed during Encystation and at Mature Cysts

“…The role of proteases in encystation of the amoeba is also unknown. Only a few molecules, including ubiquitin-like Atg8 and enolase, have been reported to be associated with encystation [39,40]. Given the specific expression of NfCPI during encystation of N. fowleri, it could play a critical role in regulating the proteolytic activities of cysteine proteases, mediating the encystation process or mature cyst formation in amoeba.…”