P10 : Tissue-specific pattern of PI3K-Akt signaling during freezing in wood frog, Rana sylvatica

Abstract

Wood frogs, Rana sylvatica, can survive under freezing conditions. Biochemical adaptations including metabolic rate depression and regulations on key cell signal transduction pathways ensure their survival. The serine/threonine kinase Akt (or Protein Kinase B, PKB), which is mainly involved in the growth factor re gulated PI3K (phosphoinositide-3-kinase)-Akt pathway, has been considered as one of the most important cell signaling components. The pathway rapidly held the spotlight because of its abundant downstream effects – protein synthesis (related to mRNA translation), cell survival (related to apoptosis), cell proliferation (related to cell cycle), glucose metabolism, etc. The present study examined the tissue specific regulation patterns of Akt pathway in wood frog during freezing exposure, as well as that after the thawing treatment. The results showed that the level of active phospho-form of Akt was down-regulated in muscle, liver and kidney, but not in liver during freezing. The level of the main Akt activity inhibitor PTEN decreased in liver significantly under stress. The select downstream targets of Akt (p21, TSC2, Cyclin D1) also showed corresponding responses in each tissue. Accordingly, the data demonstrated that Akt pathway is activated in liver, but not in muscle, heart and kidney in wood frog during freezing exposure.