Translational initiation is uncoupled from elongation at 18° C during mammalian hibernation

Cellular and organismal homeostasis must be maintained across a body temperature (T-b) range of 0 to 37 degreesC during mammalian hibernation. Hibernators depress biosynthetic activities including protein synthesis, concordant with limited energy availability and temperature effects on reaction rates. We used polysome analysis to show that initiation of protein synthesis ceases during entrance into torpor in golden-mantled ground squirrels (Spermophilus lateralis) when T-b reaches 18 degreesC. Elongation of preinitiated polypeptides continues slowly throughout the torpor bout. As T-b begins to rise, initiation resumes even at temperatures below 18 degreesC, although the euthermic polysome pattern is not reestablished. At precisely 18 degreesC, there is a large increase in initiation events and a complete restoration of euthermic polysome distribution patterns. These data indicate a role for both passive and active depression of translation during torpor and are consistent with a requirement for new protein biosynthesis during each interbout arousal.