A Biochemical Comparison of Proteases from Pathogenic Naegleria fowleri and Non‐Pathogenic Naegleria gruberi

Abstract

Naegleria fowleri is the etiologic agent of primary amoebic meningoencephalitis (PAM). Proteases have been suggested to be involved in tissue invasion and destruction during infection. We analyzed and compared the complete protease profiles of total crude extract and conditioned medium of both pathogenic N. fowleri and non-pathogenic Naegleria gruberi trophozoites. Using SDS-PAGE, we found differences in the number and molecular weight of proteolytic bands between the two strains. The proteases showed optimal activity at pH 7.0 and 35 degrees C for both strains. Inhibition assays showed that the main proteolytic activity in both strains is due to cysteine proteases although serine proteases were also detected. Both N. fowleri and N. gruberi have a variety of different protease activities at different pH levels and temperatures. These proteases may allow the amoebae to acquire nutrients from different sources, including those from the host. Although, the role of the amoebic proteases in the pathogenesis of PAM is not clearly defined, it seems that proteases and other molecules of the parasite as well as those from the host, could be participating in the damage to the human central nervous system.

Naegleria fowleri after 50 years: is it a neglected pathogen?

“…Another study showed the presence of a differential pattern of degradation between N. fowleri and N. gruberi in total crude extracts and in the conditioned medium. The authors found mainly cysteine proteases and small amounts of serine proteases in N. fowleri (Serrano-Luna et al, 2007). The same group demonstrated a mucinase activity in total crude extracts of N. fowleri (Cervantes-Sandoval et al, 2008b).…”

“…When an infection of the protozoan occurs, it can damage tissues after the invasion to the CNS. A broad battery of mechanisms, such as poreforming proteins, proteases and adhesion-mediating glycoproteins, among others, are involved in the pathogenic mechanisms through which N. fowleri acts (Aldape et al, 1994;Herbst et al, 2002;Serrano-Luna et al, 2007;Shibayama et al, 2013) (Fig. 1a).…”

A Trojan horse mechanism of bacterial pathogenesis against nematodes

“…However, the chemical nature of these volatile organic compounds (VOCs) remains largely unknown (15, 17). Recently, it was found that nematoxic bacterium P. aeruginosa can produce acylated homoserine lactones, the signal molecules in quorum sensing, as attractants for nematodes (7).A common group of virulence factors shared among bacterial pathogens are the proteases, and protease inhibitors have proven effective therapeutic agents in treating infectious diseases in vertebrates (18,19). For example, in the pathogenic bacterium E. faecalis both gelatinase and serine protease are required for systemic infections in mammalian hosts (15,20,21).…”

“…A common group of virulence factors shared among bacterial pathogens are the proteases, and protease inhibitors have proven effective therapeutic agents in treating infectious diseases in vertebrates (18,19). For example, in the pathogenic bacterium E. faecalis both gelatinase and serine protease are required for systemic infections in mammalian hosts (15,20,21).…”

Biology and pathogenesis of Naegleria fowleri

“…fowleri exhibit extracellular proteolytic activity (92,94) that degrade zonula occludens-1 (ZO-1) and claudin-1 proteins but not occludin (95). The optimal protease activity is observed at pH 7.0 and 35°C and activity can be inhibited mainly using cysteine proteases inhibitors, while serine protease activity is also observed (94).…”