Naegleria fowleri: contact-dependent secretion of electrondense granules (EDG).
The free living amoeba Naegleria fowleri is pathogenic to humans but also to other mammalians. These amoebae may invade the nasal mucosa and migrate into the brain causing cerebral hemorrhagic necrosis, a rapidly fatal infection. Knowledge of the cytolytic mechanism involved in the destruction of brain tissues by Naegleria trophozoites is limited. In other amoebic species, such as Entamoeba histolytica, we have previously reported the possible lytic role of small cytoplasmic components endowed with proteolytic activities, known as electrondense granules (EDG). Using transmission electron microscopy we now report that EDG, seldom found in long term cultured N. fowleri, are present in abundance in trophozoites recovered from experimental mice brain lesions. Numerous EDG were also observed in amoebae incubated with collagen substrates or cultured epithelial cells. SDS-PAGE assays of concentrated supernatants of these trophozoites, containing EDG, revealed proteolytic activities. These results suggest that EDG may have a clear role in the cytopathic mechanisms of this pathogenic amoeba.
Department of Infectomics and Molecular Pathogenesis, Center for Research and Advanced Studies, Av. IPN 2508, San Pedro Zacatenco, 07360 Mexico City, Mexico. Electronic address: bchavez@cinvestav.mx.
Bibiana
B
Chávez-Munguía
Department of Infectomics and Molecular Pathogenesis, Center for Research and Advanced Studies, Av. IPN 2508, San Pedro Zacatenco, 07360 Mexico City, Mexico.
Lizbeth Salazar
LS
Villatoro
School of Superior Studies Iztacala, Medicine, UNAM, Tlalnepantla, Mexico.
Maritza
M
Omaña-Molina
School of Superior Studies Iztacala, Medicine, UNAM, Tlalnepantla, Mexico.
Marco Aurelio
MA
Rodríguez-Monroy
Department of Infectomics and Molecular Pathogenesis, Center for Research and Advanced Studies, Av. IPN 2508, San Pedro Zacatenco, 07360 Mexico City, Mexico.
Norma
N
Segovia-Gamboa
Department of Infectomics and Molecular Pathogenesis, Center for Research and Advanced Studies, Av. IPN 2508, San Pedro Zacatenco, 07360 Mexico City, Mexico.
Adolfo
A
Martínez-Palomo
D000562:Amebiasis / Q000469:parasitology*; D000818:Animals; D001921:Brain / Q000469:parasitology / Q000473:pathology; D020808:Central Nervous System Protozoal Infections / Q000469:parasitology*; D003094:Collagen / Q000378:metabolism; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000469:parasitology; D061985:Madin Darby Canine Kidney Cells; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D046529:Microscopy, Electron, Transmission; D016848:Naegleria fowleri / Q000378:metabolism* / Q000472:pathogenicity / Q000648:ultrastructure; D022142:Secretory Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D014774:Virulence
D003094:Collagen
Cytolysis; Encephalitis; Free-living amoebae; Proteolytic activity; Secretion