iTRAQ-based quantitative proteomic analysis identified Eno1 as a cadmium stress response gene in Propsilocerus akamusi (Tokunaga) hemolymph.

Propsilocerus akamusi (Tokunaga) is a common species of midge in Siberia, Japan, and China and an important prey species for fish and aquatic birds. Furthermore, this species has been shown to have an extraordinary capacity to resist cadmium (Cd) toxicity. In this study, isobaric tags for relative and absolute quantitation (iTRAQ) coupled liquid chromatography tandem mass spectrometry (LC-MS/MS) was used to analyze relative changes in the P. akamusi hemolymph proteome following exposure to a sublethal concentration of Cd2+. The results showed that Cd2+ stress affects energy metabolism in P. akamusi. After examining the differentially expressed proteins (DEPs), only one up-regulated protein associated with metabolism, α-enolase (Eno1) was identified and further isolated and characterized. Sequence alignments showed that the deduced P. akamusi Eno1 amino acid sequence is highly conserved, with similarities of 77–95% noted when compared to other Dipteran Eno1 sequences. Furthermore, prolonged Cd2+ exposure impacted Eno1 transcription, protein expression and enzyme activity levels. These results suggest that Eno1 may play a role in the response to Cd2+ stress in P. akamusi.