Dysregulation of SUMOylation During Hibernation

Abstract

Hibernation is a dynamic process wherein animals oscillate between states of torpor and interbout arousal (IBA). IBA is characterized by a return to euthermy from the low temperatures and depressed metabolic rates of torpor. During late torpor (LT), the golden‐mantled ground squirrel, Spermophilus lateralis, must survive temperatures as low as −2º C at only 1% of active metabolic rates. As a result, cells may lose the ability to regulate key processes such as SUMOylation, which is involved in protein stabilization and transcriptional regulation. It has recently been shown that SUMO‐conjugate levels increase significantly during torpor. Here we present evidence that the observed increase in SUMO‐conjugate levels results from an inability to regulate SUMOylation at the low temperatures of torpor. We show that SUMOylation occurs at >20% of maximum rates at 0º C and that SUMOylation rates are not significantly different between LT, IBA, or summer active (SA) lysates at temperatures spanning 0º C to 37º C. We propose that the observed increase in SUMO‐conjugate levels during torpor is due to an inability to regulate SUMOylation combined with reduced de‐SUMOylation rates, rather than an increase in SUMOylation rates. We are currently working to identify targets of SUMOylation during hibernation, and relate these findings to their relevant cellular processes.