The involvement of an integrin-like protein and protein kinase C in amoebic adhesion to fibronectin and amoebic cytotoxicity

Abstract

Adherence of a pathogen to the host cell is one of the critical steps in microbial infections. Naegleria fowleri, a causative agent of primary amoebic meningoencephalitis in humans, is expected to interact with extracellular components of the host, such as fibronectin, in a receptor-mediated mode. In this study, we investigated the interaction between N. fowleri and fibronectin to understand its cytopathology. In binding assays using immobilized fibronectin, the number of amoebae bound to fibronectin was increased compared to the controls, and was dependent on the amount of coated fibronectin present. A fibronectin binding protein of 60 kDa was found in extracts of N. fowleri. Western blot and immunolocalization assays using integrin a 5 /FnR antibodies showed that a 60 kDa protein reacted with the antibodies in extracts of N. fowleri, which was localized on the surface of N. fowleri. Preincubation of N. fowleri with the integrin antibodies significantly inhibited amoebic binding to fibronectin and cytotoxicity to the CHO cells. Additionally, protein kinase C activity was detected in the extract of N. fowleri. When N. fowleri was pretreated with protein kinase C activator or inhibitor, the abilities of amoebic adhesion to fibronectin and cytotoxicity to the host cells were markedly affected compared to untreated amoebae. These results suggest that an amoebic integrin-like receptor and protein kinase C play important roles in amoebic cellular processes in response to fibronectin.

Pathogenic Naegleria fowleri and non-pathogenic Naegleria lovaniensis exhibit differential adhesion to, and invasion of, extracellular matrix proteins

“…Species of Acanthamoeba have been reported to bind to laminin-1, collagen IV and fibronectin (Gordon et al, 1993 et al, 2001). Consistent with these observations, it has been reported that N. fowleri binds to immobilized fibronectin in a concentration-dependent manner through the mediation of a 60 kDa fibronectin-binding protein (Han et al, 2004).In the present study the binding and invasive properties of thermotolerant pathogenic N. fowleri were compared with those of a thermotolerant non-pathogenic species, Naegleria lovaniensis. Adhesion to ECM components was shown to differ between the two species, with a higher level of adhesion observed for N. fowleri.…”

“…It has been reported previously that protozoa that are pathogenic recognize components of the ECM (Gordon et al, 1993;Han et al, 2004;Rocha-Azevedo et al, 2007Shibayama et al, 2003). For example, Entamoeba histolytica binds to ECM components, an interaction that may play an important role in its penetration of the intestinal mucosa (de Lourdes Muñoz et al, 2001;Li et al, 1995; Talamás-Rohana & Meza, 1988).…”

Disruption of MDCK cell tight junctions by the free-living amoeba Naegleria fowleri

“…For many micro-organisms, adherence is one of the most important features observed during the early invasion of different tissues or organs (Kucknoor et al, 2005;McCoy et al, 1994;Panjwani, 2010). N. fowleri is known to adhere to different cell types in a process that involves glycoconjugates as well as extracellular matrix proteins, such as fibronectin and collagen (Cervantes-Sandoval et al, 2010;Han et al, 2004;Shibayama et al, 2003). During the initial adherence step, N. fowleri may activate intracellular signals that could be important for traversing epithelial cells.…”

Biology and pathogenesis of Naegleria fowleri

“…fowleri to bind to nasal mucosa, locomotion, and chemotactic response to nerve cell components play a substantial role in disease progression (68)(69)(70) …”