Korean J Parasitol.  2013 Oct;51(5):497-502.

Identification of Atg8 Isoform in Encysting Acanthamoeba

  • 1Department of Parasitology, Kyungpook National University School of Medicine, Daegu 700-422, Korea.
  • 2Department of Parasitology, Dong-A University College of Medicine, Busan 602-714, Korea. hhkong@dau.ac.kr


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.


Acanthamoeba castellanii; encystation; autophagy protein 8; isoform

MeSH Terms

Acanthamoeba castellanii/cytology/*genetics/physiology
Amino Acid Sequence
Cell Membrane/metabolism
DNA, Protozoan/chemistry/genetics
Gene Dosage
Gene Silencing
Genes, Reporter
Molecular Sequence Data
Protein Isoforms
Protozoan Proteins/*genetics/metabolism
RNA, Messenger/genetics
RNA, Protozoan/genetics
RNA, Small Interfering/chemical synthesis/genetics
Recombinant Fusion Proteins
Sequence Alignment
DNA, Protozoan
Protein Isoforms
Protozoan Proteins
RNA, Messenger
RNA, Protozoan
RNA, Small Interfering
Recombinant Fusion Proteins
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