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INFLAMMATION AND CYTOKINES

Constitutive roles for inducible genes: evidence for the alteration in expression of the inducible hsp70 gene in Antarctic notothenioid fishes

Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California 93106-9610

Submitted 2 April 2004 ; accepted in final form 23 April 2004

Previous research on the Antarctic notothenioid fish Trematomus bernacchii demonstrated the loss of the heat shock response (HSR), a classical cellular defense mechanism against thermal stress, characterized by the rapid synthesis of heat shock proteins (Hsps). In the current study, we examined potential mechanisms for the apparent loss of the HSR in Antarctic notothenioids and, in addition, compared expression patterns of two genes from the 70-kDa Hsp family (hsc71 and hsp70) in tissues from T. bernacchii to expression patterns in tissues of two closely related temperate notothenioid fishes from New Zealand, Bovichtus variegatus and Notothenia angustata. The results showed that transcript for both the constitutive and inducible genes in the Hsp70 gene family were expressed in detectable levels in all three species. However, only the cold-temperate New Zealand fishes displayed the ability to upregulate the inducible transcript, hsp70. Although hsp70 was present in detectable levels in several tissues of the Antarctic notothen T. bernacchii, in vitro thermal stresses failed to produce a significant increase in mRNA levels. In all species, the expression of the constitutive transcript hsc71 was variable and nonresponsive to temperature increases, even at temperatures as high as 10°C above the ecologically relevant range for the species under study. Field-collected tissues from T. bernacchii (sampled immediately after capture) indicated that hsp70 mRNA was expressed at high levels in field-acclimatized fishes. Thus upregulation of molecular chaperones suggested that low-temperature stress may be significantly denaturing to cellular proteins in Antarctic fish, an observation that was supported by elevated levels of ubiquitin-conjugated protein.

heat shock response; molecular chaperones; heat shock proteins; gene expression; cold adaptation; hsp70 messenger ribonucleic acid

This article has been cited by other articles:

				S. P. Place and G. E. Hofmann Comparison of Hsc70 orthologs from polar and temperate notothenioid fishes: differences in prevention of aggregation and refolding of denatured proteins Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2005; 288(5): R1195 - R1202. [Abstract] [Full Text] [PDF]