Gene expression of components of the insulin/insulin-like signaling pathway in response to heat stress in the garter snake,Thamnophis elegans

Abstract

The insulin/insulin-like signaling (IIS) pathway is an evolutionary conserved molecular signaling pathway that regulates growth, reproduction, stress resistance, and longevity in response to nutrition and external stress. While the constituents of this pathway and their functions are relatively well understood in laboratory model animals, they have not been explored in many other organisms, with notable exceptions in the fisheries literature. We tested for the gene expression of four key components of this pathway in the garter snake (Thamnophis elegans) liver, and determine how the transcription of these components responds to heat stress. We found that the two insulin-like growth factor ligands (IGF-1 and IGF-2) and the receptors (IGF-1 Receptor and M6P/IGF-2 Receptor, or IGF-1R and IGF-2R) are expressed in garter snake liver tissue. Under normal laboratory conditions, IGF-2 and IGF-2R are expressed at a higher level than IGF-1 and IGF-1R. In response to heat stress, IGF-1 expression remained the same, IGF-2 expression decreased, and the expression of both receptors increased. These results demonstrate that elements of the IIS pathway are responsive to heat stress in snakes. Further studies are needed to fully understand the biological consequences of this response.