Protein molecular responses of field-collected oysters Crassostrea hongkongensis with greatly varying Cu and Zn body burdens

Highlights: • The first quantitative shotgun proteomic study on Cu and Zn hyperaccumulation in oysters. • Reactive oxygen species induction was the main toxicity of excess Cu and Zn targeting proteins. • Reorganization of cytoskeleton and suppression of membrane mobility were identified. • Elevated ribosome activity and strengthened degradation of misfolded proteins compensated the damage of proteins. • Reducing production of endogenous ROS and enhancing detoxification of ROS for survival under metal stress. The oyster Crassostrea hongkongensis is an ideal biomonitor due to its widespread distribution along the coast of Southern China and the ability to hyperaccumulate metals including Cu and Zn. In this study, we conducted the first investigation of the molecular responses to metal hyperaccumulation based on quantitative shotgun proteomics technique and genome information. Gill tissue of oysters collected from the uncontaminated environment (Site 1, 59.6 μg/g and 670 μg/g dry weight for Cu and Zn) displayed significant protein profile differentiation compared to those from a moderately contaminated (Site 2, 1,465 μg/g and 10,170 μg/g for Cu and Zn) and a severely contaminated environment (Site 3, 3,899 μg/g and 39,170 μg/g for Cu and Zn). There were 626 proteins identified to be differentially expressed at Site 3 but only 247 proteins at Site 2. Oysters from a moderately contaminated estuary (Site 2) displayed fewer effects as compared to oysters under severe contamination, with fluctuated small molecule metabolism and enhanced translation process. At Site 3, the induction of reactive oxygen species (ROS) was the main toxicity under the extremely high level of metal stress, which resulted in protein damage. Additionally, the impaired structure of cytoskeleton and modified membrane tracking process at Site 3 oysters led to the blockage or less efficient protein or macromolecule distribution within cells. Nonetheless, proteomic analysis in this study revealed that oysters could partly alleviate the adverse metal effects by boosting the translation process, enhancing the ability to recycle the misfolded proteins, and enhancing the potential to eliminate the excess ROS. Our study demonstrated an adaptive potential of oysters at the protein level to survive under conditions of metal hyper-accumulation.