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Inside JEB |
ESTIVATOR'S ALTERNATIVE APPROACH
kathryn{at}biologists.com
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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 2
(eIF2) is a key component of
transcriptional machinery, but when eIF2 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 eIF2 to switch off protein synthesis and
save energy. They found that the frogs had high levels of phosphorylated
eIF2 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 eIF2, whether
or not they were estivating (p.
2363).
Having found that frogs downregulate their metabolism by depressing protein
synthesis, Guppy hopes to find the signal that triggers eIF2
phosphorylation. However, it's less clear how snails regulate their metabolic
rate by phosphorylating eIF2, or whether they have opted for an
alternative approach that is yet to be discovered.
References
Pakay, J. L., Hobbs, A. A., Kimball, S. R. and Guppy, M.
(2003). The role of eukaryotic initiation factor 2 during
the metabolic depression associated with estivation. J. Exp.
Biol. 206,2363
-2371.
Related articles in JEB:
during the metabolic depression associated with estivation
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