Abstract
Protein synthesis is depressed during mammalian hibernation in concordance with metabolic demands. In the absence of significant protein synthesis, continued proteolysis would rapidly deplete protein pools. Since ubiquitin-dependent proteolysis is implicated in the turnover of most regulatory proteins, we examined the fate of this system during hibernation. Ubiquitin-dependent proteolysis consists of two major steps: (1) the tagging of a protein substrate by ubiquitin and (2) the protein substrate’s subsequent degradation by the 26S proteasome. An earlier study revealed a two to threefold elevation of ubiquitin conjugate concentrations during hibernation: an unexpected result that seemingly would suggest increased proteolytic activity. A more likely explanation for these data would be that proteolysis per se was depressed and that the increased levels of ubiquitylated proteins reflect an inability to degrade tagged proteins. We employed an assay based on the cleavage of fluorogenic substrates to address the well characterized proteolytic activities of the proteasome. All activities show little to no activity at temperatures associated with deep torpor. Coordinated depression of proteolytic activities by low temperature supports the hypothesis that the increased levels of ubiquitylated proteins during hibernation is explained by a net accumulation due to an inability to degrade the tagged proteins.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Ahlberg J, Berkenstam A, Henell F, Glaumann H (1985) Degradation of short and long lived proteins in isolated rat liver lysosomes. J Biol Chem 260:5847–5854
Carey HV, Andrews MT, Martin SL (2003) Mammalian hibernation: cellular and molecular responses to depressed metabolism and low temperature. Physiol Rev 83:1153–1181
Chen Y, Matsushita M, Nairn AC, Damuni Z, Cai D, Frerichs KU, Hallenbeck JM (2001) Mechanisms for increased levels of phosphorylation of elongation factor-2 during hibernation in ground squirrels. Biochem 40:11565–11570
Ciechanover A, Finley D, Varshavsky A (1984) Ubiquitin dependence of selective protein degradation demonstrated in the mammalian cell cycle mutant ts85. Cell 37:57–66
Dice JF (1987) Molecular determinants of protein half-lives in eukaryotic cells. FASEB J 1:349–357
Frerichs KU, Smith CB, Brenner M, DeGracia DJ, Krause GS, Marrone L, Dever TE, Hallenbeck JM (1998) Suppression of protein synthesis in brain during hibernation involves inhibition of protein initiation and elongation. Proc Natl Acad Sci 95:14511–14516
Harding CV, Unanue ER (1990) Low-temperature inhibition of antigen processing and iron uptake from transferrin: deficits in endosome functions at 18°C. Eur J Immunol 20:323–329
Hough R, Rechsteiner M (1984) Effects of temperature on the degradation of proteins in rabbit reticulocyte lysates and after injection into HeLa cells. Proc Natl Acad Sci 81:90–94
Kisselev AF, Akopian TN, Castillo V, Goldberg AL (1999) Proteasome active sites allosterically regulate each other, suggesting a cyclical bite-chew mechanism for protein breakdown. Mol Cell 4:395–402
Lee DH, Goldberg AL (1998) Proteasome inhibitors: valuable new tools for cell biologists. Trends Cell Biol 8:397–403
Martin SL, Maniero GD, Carey C, Hand SC (1999) Reversible depression of oxygen consumption in isolated liver mitochondria during hibernation. Physiol Biochem Zool 72:255–264
Müller M, Dubiel W, J. Rathmann, and S. Rapoport (1980) Determination and characteristics of energy-dependent proteolysis in rabbit reticulocytes. Eur J Biochem 109:405–410
Munro S, Pelham H (1985) What turns on heat shock genes?. Nature 317:477–478
Orlowski M, Wilk S (2000) Catalytic activities of the 20S proteasome, a multicatayltic proteinase complex. Arch Biochem Biophys 383:1–16
Pickart CM, Cohen RE (2004) Proteasomes and their kin: proteasomes in the machine age. Nat Rev Mol Cell Biol 5:177–187
Rock KL, Goldberg AL (1999) Degradation of cell proteins and the generation of MHC class I-presented peptides. Annu Rev Immunol 17:739–779
Rock KL, Gramm C, Rothstein L, Clark K, Stein R, Dick L, Hwang D, Goldberg AL (1994) Inhibitors of the proteosome block the degradation of most cell proteins and the generation of peptides presented on MHC class I molecules. Cell 78:761–771
Roederer M, Bowser R, Murphy RF (1987) Kinetics and temperature dependence of endocytosed material to proteolytic enzymes and low pH: evidence for a maturation model for the formation of lysosomes. J Cell Physiol 131:200–209
Rogers S, Wells R, Rechsteiner M (1986) Amino acid sequences common to rapidly degraded proteins: the PEST hypothesis. Science 234:364–368
Rolfe DFS, Brown GC (1997) Cellular energy utilization and molecular origin of standard metabolic rate in mammals. Physiol Rev 77:731–758
Schmidt H, Siems W, Müller M, Dumdey R, Rapoport SM (1991) ATP-producing and consuming processes of Ehrlich mouse ascites tumor cells in proliferating and resting phases. Exp Cell Res 194:122–127
Schrader M, Schulz-Knappe P (2001) Peptidomics technologies for human body fluids. Trends Biotech 19(Suppl):S55–S60
van Breukelen F, Carey HV (2002) Ubiquitin conjugate dynamics in the gut and liver of hibernating ground squirrels. J Comp Physiol B 172:269–273
van Breukelen F, Hand SC (2000) Characterization of ATP-dependent proteolysis in embryos of the brine shrimp, Artemia franciscana. J Comp Physiol B 170:125–133
van Breukelen F, Martin SL (2001) Translational inititiation is uncoupled from elongation at 18°C during mammalian hibernation. Am J Physiol Regul Integr Comp Physiol 281:R1374–R1379
van Breukelen F, Martin SL (2002) Molecular adaptations in mammalian hibernators: unique adaptations or generalized responses? J Appl Physiol 92:2640–2647
van Breukelen F, Sonenberg N, Martin S (2004) Seasonal and state dependent changes of eIF4E and 4E-BP1 during mammalian hibernation: implications for the control of translation during torpor. Am J Physiol Regul Integr Comp Physiol 287:R349–R353
Zhegunov GF, Mikulinsky YE, Kudokotseva EV (1988) Hyperactivation of protein synthesis in tissues of hibernating animals on arousal. Cryo Lett 9:236–245
Acknowledgements
Bryan Lloyd was supported by an American Physiological Society Summer Student Fellowship. Support for this project was also made through the National Science Foundation (IOB 0448396). The use of animals in these experiments comply with the current laws of the country in which the experiments were performed and were approved by the Institutional Animal Care and Use Committee of the University of Nevada, Las Vegas.
Author information
Authors and Affiliations
Corresponding author
Additional information
Communicated by H.V. Carey
Rights and permissions
About this article
Cite this article
Velickovska, V., Lloyd, B.P., Qureshi, S. et al. Proteolysis is depressed during torpor in hibernators at the level of the 20S core protease. J Comp Physiol B 175, 329–335 (2005). https://doi.org/10.1007/s00360-005-0489-x
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00360-005-0489-x