Is cold the new hot? Elevated ubiquitin-conjugated protein levels in tissues of Antarctic fish as evidence for cold-denaturation of proteins in vivo

Abstract

Levels of ubiquitin (Ub)-conjugated proteins, as an index of misfolded or damaged proteins, were measured in notothenioid fishes, with both Antarctic (Trematomus bernacchii, T. pennellii, Pagothenia borchgrevinki) and non-Antarctic (Notothenia angustata, Bovichtus variegatus) distributions, as well as non-notothenioid fish from the Antarctic (Lycodichthys dearborni, Family Zoarcidae) and New Zealand (Bellapiscis medius, Family Tripterygiidae), in an effort to better understand the effect that inhabiting a sub-zero environment has on maintaining the integrity of the cellular protein pool. Overall, levels of Ub-conjugated proteins in cold-adapted Antarctic fishes were significantly higher than New Zealand fishes in gill, liver, heart and spleen tissues suggesting that life at sub-zero temperatures impacts protein homeostasis. The highest tissue levels of ubiquitinated proteins were found in the spleen of all fish. Ub conjugate levels in the New Zealand N. angustata, more closely resembled levels measured in other Antarctic fishes than levels measured in other New Zealand species, likely reflecting their recent shared ancestry with Antarctic notothenioids.

Transcriptomic and genomic evolution under constant cold in Antarctic notothenioid fish

“…The augmented need for cellular protein homeostasis is also indicated in the upregulation of genes in ubiquitin-dependent protein degradation pathways (Fig. 2Bii) and support the reported high levels of ubiquitin-conjugated proteins in Antarctic notothenioid tissues (25). Besides genes in intracellular protein catabolism, transcripts of several extracellular proteases such as Cathepsin Z and MMP-17 homolog (Fig.…”

Larval excretory-secretory products from the parasite Schistosoma mansoni modulate HSP70 protein expression in defence cells of its snail host, Biomphalaria glabrata

“…Intensities of immuno-reactive bands on blots from three independent experiments were measured and mean HSP70 expression levels calculated (b), with respect to control values represented by 1 and shown as the dotted line. **P≤ 0.01 when compared to DMSO controls (n=6, ±SEM) Discussion Aquatic organisms exhibit altered HSP expression when exposed to range of stressful conditions including seasonal acclimatisation, climate change (increase and decrease in temperature), competition for space, food availability, wave exposure, heavy metal exposure and laboratory adaptation (Buckley et al 2001;Franzellitti and Fabbri 2005;Helmuth et al 2002;Helmuth and Hofmann 2001;Kefaloyianni et al 2005;Lund et al 2006;Todgham et al 2007;Tomanek and Sanford 2003). For molluscs, HSP-like molecules have been identified in the sea slug, Aplysia californica, the oysters, Crassostrea virginica, O. edulis, and Crassostrea gigas, the mussel, Mytilus galloprovincialis, and the clams Tapes philippinarum and Scapharca inaequivalvis (Kuhl et al 1992;Piano et al 2002Piano et al , 2004Tirard et al 1995).…”

Cod and climate in a latitudinal cline: physiological analyses of climate effects in marine fishes

“…Rates of damage may be elevated due to trade-offs between enhanced protein flexibility required for function at cold temperature and the associated loss in stability (Fields 2001). Elevated levels of ubiquitin-bound proteins have, in fact, been found and interpreted as indicators of enhanced protein damage due to instability in coldadapted Antarctic notothenioids (Todgham et al 2007). Alternatively and as with elevated RNA levels, enhanced levels of ubiquitin-bound proteins in the cold may rather reflect cold-adjusted steady state levels at limited extra cost.…”