title: The effect of temperature adaptation on the ubiquitin-proteasome pathway in notothenioid fishes.
abstract: There is an accumulating body of evidence suggesting that the sub-zero Antarctic marine environment places physiological constraints on protein homeostasis. Levels of ubiquitin (Ub)-conjugated proteins, 20S proteasome activity and mRNA expression of many proteins involved in both the Ub tagging of damaged proteins as well as the different complexes of the 26S proteasome were measured to examine whether there is thermal compensation of the Ub-proteasome pathway in Antarctic fishes to better understand the efficiency of the protein degradation machinery in polar species. Both Antarctic (Trematomus bernacchii, Pagothenia borchgrevinki) and non-Antarctic (Notothenia angustata, Bovichtus variegatus) notothenioids were included in this study to investigate the mechanisms of cold adaptation of this pathway in polar species. Overall, there were significant differences in the levels of Ub-conjugated proteins between the Antarctic notothenioids and B. variegatus, with N. angustata possessing levels very similar to those of the Antarctic fishes. Proteasome activity in the gills of Antarctic fishes demonstrated a high degree of temperature compensation such that activity levels were similar to activities measured in their temperate relatives at ecologically relevant temperatures. A similar level of thermal compensation of proteasome activity was not present in the liver of two Antarctic fishes. Higher gill proteasome activity is likely due in part to higher cellular levels of proteins involved in the Ub-proteasome pathway, as evidenced by high mRNA expression of relevant genes. Reduced activity of the Ub-proteasome pathway does not appear to be the mechanism responsible for elevated levels of denatured proteins in Antarctic fishes, at least in the gills.
authors.affiliation: Department of Animal Science, University of California, Davis, Davis, CA 95616, USA todgham@ucdavis.edu.
authors.forename: Anne E
authors.identifier: http://orcid.org/0000-0003-1439-6985
authors.initials: AE
authors.lastname: Todgham
authors.affiliation: Department of Biology, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Crombie
authors.affiliation: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
authors.forename: Gretchen E
authors.initials: GE
authors.lastname: Hofmann
mesh_terms: D000064:Acclimatization; D000818:Animals; D000864:Antarctic Regions; D003080:Cold Temperature; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D010473:Perciformes / Q000502:physiology*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism*
chemical_list: D029941:Fish Proteins; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex
keywords: Antarctic fish; Cold adaptation; Notothenioid; Protein homeostasis; Ub–proteasome pathway