Roles for lysine acetyltransferases during mammalian hibernation

The thirteen-lined ground squirrel (Ictidomys tridecemlineatus) is a well-known model for studying hibernation. While in a torpid state, these animals globally suppress energy expensive processes, while supporting specialized pathways necessary for survival. Lysine acetyltransferases (KATs) play a crucial role in modulating the expression and activity of a wide-variety of cellular pathways and processes, and therefore, may play a role during hibernation when the cell is shifting to an energy conservative, cytoprotective state. Here we measured protein levels of four KATs (CBP, PCAF, GCN5L2, HAT1), total histone acetyltransferase (HAT) activity, and the levels of acetylation of histone H3 lysine 9 (H3K9ac), in multiple tissues across the torpor-arousal cycle. Our results show a tissue-specific response of KATs, particularly in the adipose tissues where specific KATs (PCAF and GCN5L2), HAT activity, and H3K9ac increased in the metabolically active BAT while HAT1, HAT activity and H3K9ac decreased in WAT. Liver showed significant increases in the KAT PCAF whereas skeletal muscle had decreased CBP and GCN5L2. Both liver and skeletal muscle showed no change in HAT activity and H3K9me3 increased in muscle during torpor. Together, these results suggest KATs may play specialized roles in the different tissues of the ground squirrel to contribute to the hibernator phenotype.