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

Levels of ubiquitin (Ub)-conjugated proteins, as an index of misfolded or damaged proteins, were measured in notothenioid Wshes, with both Antarctic (Trematomus bernacchii, T. pennellii, Pagothenia borchgrevinki) and non-Antarctic (Notothenia angustata, Bovichtus variegatus) distributions, as well as non-notothenioid Wsh from the Antarctic (Lycodichthys dearborni, Family Zoarcidae) and New Zealand (Bellapiscis medius, Family Tripterygiidae), in an eVort to better understand the eVect 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 Wshes were signiWcantly higher than New Zealand Wshes 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 Wsh. Ub conjugate levels in the New Zealand N. angustata, more closely resembled levels measured in other Antarctic Wshes than levels measured in other New Zealand species, likely reXecting their recent shared ancestry with Antarctic notothenioids.