Characterization of Sarcocystis fayeri's actin‐depolymerizing factor as a toxin that causes diarrhea

• Published in: Genes to cells : devoted to molecular & cellular mechanisms Vol. 22; no. 9; pp. 825 - 835
• Main Authors: Irikura, Daisuke, Saito, Morihiro, Sugita‐Konishi, Yoshiko, Ohnishi, Takahiro, Sugiyama, Kei‐ichi, Watanabe, Maiko, Yamazaki, Akiko, Izumiyama, Shinji, Sato, Hirotaka, Kimura, Yusuke, Doi, Rie, Kamata, Yoichi
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.09.2017
• Subjects: Actin; Actin Depolymerizing Factors - chemistry; Actin Depolymerizing Factors - toxicity; Actin-depolymerizing protein; ADF/cofilin protein; Amino acid sequence; Animals; Cell culture; Cell Line; Cofilin; Conserved Sequence; Cysts; Cytotoxicity; Diarrhea; Diarrhea - parasitology; Fibroblasts; Fibroblasts - drug effects; Fibroblasts - metabolism; Food contamination & poisoning; Food poisoning; Homology; Ileum; Intestinal Mucosa - drug effects; Intestinal Mucosa - parasitology; Intestine; Macrophages; Macrophages - drug effects; Macrophages - metabolism; Mice; Mucosa; Parasites; Polymerase chain reaction; Protein Domains; Proteins; Protozoan Proteins - chemistry; Protozoan Proteins - toxicity; Rabbits; Sarcocystis - pathogenicity; Toxins, Biological - chemistry; Toxins, Biological - toxicity; Tumor Necrosis Factor-alpha - genetics; Tumor Necrosis Factor-alpha - metabolism
• ISSN: 1356-9597; 1365-2443; 1365-2443
• DOI: 10.1111/gtc.12515

Raw horsemeat has the potential to induce food poisoning which often presents with diarrheal symptoms. A sample of horsemeat was found to be infected with Sarcocystis fayeri, and a 15‐kDa protein isolated from the cysts of S. fayeri was found to clearly show its diarrhea‐inducing activity. A nested polymerase chain reaction was used to clone the cDNA of the 15‐kDa protein. The deduced amino acid sequence showed homology to actin‐depolymerizing factor (ADF). A recombinant 15‐kDa protein depolymerized prepolymerized actins in a test tube. The 15‐kDa protein possessed conserved amino acid sequences of ADF of Toxoplasma gondii and Eimeria tenella. These characteristics indicate that the 15‐kDa protein of S. fayeri belongs to the ADF/cofilin protein family. The recombinant 15‐kDa protein evoked fluid accumulation in the looped ileum, resulting in diarrhea, but it did not kill the cultured fibroblast cells, macrophages or intestinal mucosal cells. In addition, the culture supernatant of the macrophages treated with the recombinant 15‐kDa protein killed the fibroblast L929 cells. This fact indicates that ADF of S. fayeri induced cytotoxic substances, such as tumor necrosis factor‐α, according to the published reports. Although further experiments are needed now to elucidate the enterotoxic mechanism of S. fayeri's ADF, our findings may offer new insight into research on parasites and parasite‐instigated food poisoning. Raw horsemeat containing Sarcocystis fayeri induces food poisoning. A toxic protein of S. fayeri was identified, and its cDNA was cloned. The protein was actin‐depolymerizing factor (ADF). Its recombinant protein evoked fluid accumulation in the ileal loop test, suggesting the ADF is the cause for the food poisoning.