title: Identification of atg8 isoform in encysting Acanthamoeba.
abstract: Autophagy-related protein 8 (Atg8) is an essential component of autophagy formation and encystment of cyst-forming parasites, and some protozoa, such as, Acanthamoeba, Entamoeba, and Dictyostelium, have been reported to possess a type of Atg8. In this study, an isoform of Atg8 was identified and characterized in Acanthamoeba castellanii (AcAtg8b). AcAtg8b protein was found to encode 132 amino acids and to be longer than AcAtg8 protein, which encoded 117 amino acids. Real-time PCR analysis showed high expression levels of AcAtg8b and AcAtg8 during encystation. Fluorescence microscopy demonstrated that AcAtg8b is involved in the formation of the autophagosomal membrane. Chemically synthesized siRNA against AcAtg8b reduced the encystation efficiency of Acanthamoeba, confirming that AcAtg8b, like AcAtg8, is an essential component of cyst formation in Acanthamoeba. Our findings suggest that Acanthamoeba has doubled the number of Atg8 gene copies to ensure the successful encystation for survival when 1 copy is lost. These 2 types of Atg8 identified in Acanthamoeba provide important information regarding autophagy formation, encystation mechanism, and survival of primitive, cyst-forming protozoan parasites.
authors: Department of Parasitology, Kyungpook National University School of Medicine, Daegu 700-422, Korea.
authors: Eun-Kyung
authors: EK
authors: Moon
authors: Yeonchul
authors: Y
authors: Hong
authors: Dong-Il
authors: DI
authors: Chung
authors: Hyun-Hee
authors: HH
authors: Kong
mesh_terms: D048248:Acanthamoeba castellanii / Q000166:cytology / Q000235:genetics* / Q000502:physiology; D000562:Amebiasis / Q000469:parasitology*; D000595:Amino Acid Sequence; D001343:Autophagy; D002462:Cell Membrane / Q000378:metabolism; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D018628:Gene Dosage; D020868:Gene Silencing; D017930:Genes, Reporter; D006801:Humans; D008969:Molecular Sequence Data; D010588:Phagosomes / Q000378:metabolism; D020033:Protein Isoforms; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D016053:RNA, Protozoan / Q000235:genetics; D034741:RNA, Small Interfering / Q000138:chemical synthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins; D016415:Sequence Alignment
chemical_list: D016054:DNA, Protozoan; D020033:Protein Isoforms; D015800:Protozoan Proteins; D012333:RNA, Messenger; D016053:RNA, Protozoan; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins
keywords: Acanthamoeba castellanii; autophagy protein 8; encystation; isoform