Life in the Slow Lane: The Rate of Protein Synthesis Is Slower in the Protoendothermic Tenrec than the Boreoeutherian Golden-Mantled Ground Squirrel

Abstract

In order to address mechanisms of how hibernating mammals depress protein synthesis during torpor, we developed primary cell cultures from golden-mantled ground squirrels (Spermophilus [Callospermophilus] lateralis) and tenrecs (Tenrec ecaudatus). During torpor in squirrels, there is an acute uncoupling of translational initiation and elongation at body temperature (Tb) = 18°C as animals enter torpor. As a result, there are robust changes to the polysome profile of squirrels depending on state. Protein synthesis is depressed to 0.23 to 0.5% of active rates during torpor. In the bizarre, Afrotherian Tenrec ecaudatus, metabolism and Tb are remarkably plastic. Tenrecs may be fully active with a Tb of 12 °C or hibernating at a Tb of 28 °C. Moreover, oxygen consumption rates may vary 25 fold in active tenrecs. With this high variability in Tb, one might expect that these tenrecs might not be able to use Tb to control protein synthesis. Liver polysome profiles were confusing- there were no real changes between states or temperature. Rather, all tenrecs had a rather modest polysome profile with little heavy material typical of very active protein synthesis. To address this, we developed liver (do not grow well) and kidney cell (grow very well) cultures from ground squirrels and tenrecs. Our results indicate that the translation rate in tenrec primary cells is ~30 % of the translation rate in golden-mantled ground squirrel (p < 0.05). We interpret these results as tenrecs living ‘Life in the Slow Lane.’ By experiencing these low rates of a process critical to homeostasis, we contend tenrecs are avoiding rapid changes as a consequence of their rapid changes in Tb or metabolism. In effect, ‘driving slowly’ allows a tenrec to avoid major accidents which would imperil the animal. Perhaps not surprisingly, tenrec litters are enormous with as many as 32 confirmed young in a single litter. This research was supported by the Translational Research Institute for Space Health (TRISH). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.