When the going gets tough, it's often better to sit tight and weather it out. So when the summer sun is too high, some creatures downregulate their metabolism, and aestivate to conserve energy. One cellular process that gobbles up ATP is protein synthesis and many creatures that become dormant slow down their metabolic rate by blocking the machinery that translates mRNA into protein. Michael Guppy's group wondered whether estivating frogs and snails also block protein translation to conserve energy.
Eukaryotic initiation factor 2α (eIF2α) is a key component of transcriptional machinery, but when eIF2α is phosphorylated, it ceases to initiate translation, and protein synthesis stops. Knowing that some dormant animals used high levels of the phosphorylated protein to stop protein synthesis and conserve energy, the team tested whether estivating frogs and snails also phosphorylated eIF2α to switch off protein synthesis and save energy. They found that the frogs had high levels of phosphorylated eIF2α to reduce protein translation. But surprisingly, the snails hadn't switched off protein synthesis by phosphorylating the initiation factor, and they maintained the same level of active unphosphorylated eIF2α, whether or not they were estivating ().
Having found that frogs downregulate their metabolism by depressing protein synthesis, Guppy hopes to find the signal that triggers eIF2αphosphorylation. However, it's less clear how snails regulate their metabolic rate by phosphorylating eIF2α, or whether they have opted for an alternative approach that is yet to be discovered.
