'Identification of Protein Biomarkers Underlying Phenotypic Plasticity and Survival in the Environmental Sentinel Caenorhabditis elegans'

Abstract

Global public health is threatened by increasing risk of disease outbreaks, epidemics, industrial accidents, natural disasters and other health emergencies. Effective management of global public health is reliant upon understanding the response of an organism to its environment and in turn its development and evolution. An environmentally induced change in phenotype, termed phenotypic plasticity, allows survival in heterogeneous environments. Due to its ease of laboratory cultivation and close similarity to parasitic nematodes the genome verified free-living nematode Caenorhabditis elegans provides an ideal animal model in which phenotypic plasticity may be investigated. The developmentally arrested and environmentally resistant dauer stage in C. elegans represents a model in which the ageing process can be investigated. Numerous biochemical, metabolic and transcriptomic analyses have supported a diversion of energy consumption away from anabolic processes and towards enhanced cellular maintenance and detoxification processes. For the first time, this study confirms some of these findings on the protein level. Important components of this enhanced longevity system include the alpha-crystallin family of small heat shock proteins (HSP-12.3 and -12.6), as well as anti-ROS defence systems (including SOD-1 and glutathione peroxidise) and activity of cellular phase II detoxification processes. The multi-gene family of ubiquitous multifunctional proteins GSTs are able to detoxify a broad range of exogenous and endogenous toxins in Phase II cellular detoxification. Comparative investigations of GST complements in dauers and in long-lived daf-2 adults (in comparison to their respective L3 and wild-type controls) have found an up-regulation in daf-2 adults and in dauer larvae, respectively of Pi-class members GST-1 (CE00302) and GST-10 (CE21937) and Nu-Class members GST-5 (CE01613) and GST-7 (CE07055). The use of RNAi and recombinant technology along with synthetically available model and natural substrates has enabled functional and biochemical characterisation to begin on the most abundant of these differently expressed GSTs, GST-1 (CE00302), GST-5 (CE01613) and GST-7 (CE07055). 2DE sub- proteomics revealed that GST-1 and -7 were reduced by approximately 70-80 % and GST-5 by approximately 45 %. Furthermore, in response to RNAi knock-down of GST-1 (CE00302) GST-26 (CE22416) and GST-27 (CE22417) were significantly up-regulated (p < 0.01). Biochemical characterisation of recombinant CE00302 (GST-1), CE01613 (GST-5) and CE07055 (GST-7) has suggested a role in both detoxification of secondary metabolites of lipid peroxidation and in the transport or modification of eicanosoid signals. Furthermore, metabolic analyses of daf-2 and wild-type adults have shown possible evidence of reduced lipid peroxidation in daf-2 adults and also possibly a reduced rate of cell growth and apoptosis. Oxidative damage, as a result of both exogenous and endogenous toxins, is believed to play a role in drug-induced toxicity and in a wide array of clinical disorders (Szeto, 2005). Therefore, these GSTs may provide a useful application as biomarkers for disease and environmental contamination, as well as chemotherapeutic targets for clinical disease treatment and parasitic nematode control.