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Biol Open 2013 Aug 21;210:1057-69. doi: 10.1242/bio.20136106.
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Significant modulation of the hepatic proteome induced by exposure to low temperature in Xenopus laevis.

Nagasawa K , Tanizaki Y , Okui T , Watarai A , Ueda S , Kato T .

The African clawed frog, Xenopus laevis, is an ectothermic vertebrate that can survive at low environmental temperatures. To gain insight into the molecular events induced by low body temperature, liver proteins were evaluated at the standard laboratory rearing temperature (22°C, control) and a low environmental temperature (5°C, cold exposure). Using nano-flow liquid chromatography coupled with tandem mass spectrometry, we identified 58 proteins that differed in abundance. A subsequent Gene Ontology analysis revealed that the tyrosine and phenylalanine catabolic processes were modulated by cold exposure, which resulted in decreases in hepatic tyrosine and phenylalanine, respectively. Similarly, levels of pyruvate kinase and enolase, which are involved in glycolysis and glycogen synthesis, were also decreased, whereas levels of glycogen phosphorylase, which participates in glycogenolysis, were increased. Therefore, we measured metabolites in the respective pathways and found that levels of hepatic glycogen and glucose were decreased. Although the liver was under oxidative stress because of iron accumulation caused by hepatic erythrocyte destruction, the hepatic NADPH/NADP ratio was not changed. Thus, glycogen is probably utilized mainly for NADPH supply rather than for energy or glucose production. In conclusion, X. laevis responds to low body temperature by modulating its hepatic proteome, which results in altered carbohydrate metabolism.

PubMed ID: 24167716
PMC ID: PMC3798189
Article link: Biol Open

Species referenced: Xenopus laevis
Genes referenced: acss2.2 agl aldob ces2.8 cs fubp1 g6pd gak gbe1 gck gk gnpda1 gpd1 grhpr.1 gys1 ids pfkm pklr pkm prkg1 pygl tkt tpi1

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References [+] :
Aizawa, Expression of erythropoietin receptor-like molecule in Xenopus laevis and erythrocytopenia upon administration of its recombinant soluble form. 2005, Pubmed, Xenbase