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Shotgun Proteomics Analysis of Hibernating Arctic Ground Squirrels*

TitleShotgun Proteomics Analysis of Hibernating Arctic Ground Squirrels*
Publication TypeJournal Article
Year of Publication2010
AuthorsShao, C, Liu, Y, Ruan, H, Li, Y, Wang, H, Kohl, F, Goropashnaya, AV, Fedorov, VB, Zeng, R, Barnes, BM, Yan, J
JournalMolecular & Cellular Proteomics

Mammalian hibernation involves complex mechanisms ofmetabolic reprogramming and tissue protection. Previousgene expression studies of hibernation have mainly focusedon changes at the mRNA level. Large scale proteomicsstudies on hibernation have lagged behind largely becauseof the lack of an adequate protein database specific forhibernating species. We constructed a ground squirrel proteindatabase for protein identification and used a label-freeshotgun proteomics approach to analyze protein expressionthroughout the torpor-arousal cycle during hibernationin arctic ground squirrels (Urocitellus parryii). We identifiedmore than 3,000 unique proteins from livers of arctic groundsquirrels. Among them, 517 proteins showed significantdifferential expression comparing animals sampled after atleast 8 days of continuous torpor (late torpid), within 5 h ofa spontaneous arousal episode (early aroused), and 1–2months after hibernation had ended (non-hibernating). Consistentwith changes at the mRNA level shown in a previousstudy on the same tissue samples, proteins involved inglycolysis and fatty acid synthesis were significantly underexpressedat the protein level in both late torpid and earlyaroused animals compared with non-hibernating animals,whereas proteins involved in fatty acid catabolism were significantlyoverexpressed. On the other hand, when we comparedlate torpid and early aroused animals, there were discrepanciesbetween mRNA and protein levels for a largenumber of genes. Proteins involved in protein translation anddegradation, mRNA processing, and oxidative phosphorylationwere significantly overexpressed in early aroused animalscompared with late torpid animals, whereas no significantchanges at the mRNA levels between these stages hadbeen observed. Our results suggest that there is substantialpost-transcriptional regulation of proteins during torporarousalcycles of hibernation.

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