Identification of Candidate Protein Biomarkers Associated with Domoic Acid Toxicosis in Cerebrospinal Fluid of California Sea Lions (Zalophus californianus)

Since 1998, California sea lion (Zalophus californianus) stranding events associated with domoic acid toxicosis have consistently increased. Outside of direct measurement of DA in bodily fluids at the time of stranding, currently there are no practical non-lethal clinical tests for the diagnosis of domoic acid toxicosis (DAT) that can be utilized in a large-scale rehabilitation facility. Proteomic analysis was conducted to discover candidate protein markers of DAT using cerebrospinal fluid from stranded California sea lions with acute DAT (n = 8), chronic DAT (n = 19), or without DAT (n = 13). A total of 2005 protein families were identified experiment-wide (FDR < 0.01). Of these proteins, 83 were significantly different in abundance across the three groups (adj. p < 0.05). Cytoplasmic malate dehydrogenase (MDH1), 5-3 exonuclease PLD3, disintegrin and metalloproteinase domain-containing protein 22 (ADAM22), 14-3-3 protein gamma (YWHAG), neurosecretory protein VGF, and calsyntenin-1 (CLSTN1) were able to discriminate California sea lions with or without DAT (ROC > 0.75). Immunoglobulin kappa light chain-like (IGKV2D-28), receptor-type tyrosine-phosphatase F (PTRPF), kininogen-1 (KNG1), prothrombin (F2), and beta-synuclein (SNCB) were able to discriminate acute DAT from chronic DAT (ROC > 0.75). Interestingly, proteins involved in alpha synuclein deposition were over- represented as classifiers of DAT and many of these proteins have been implicated in a variety of neurodegenerative diseases. These proteins should be considered potential markers for DAT in California sea lions, as well as markers to discriminate between acute or chronic DAT, and should be considered priority for future validation studies as biomarkers. All MS data have been deposited in the ProteomeXchange with identifier PXD041356 (http://proteomecentral.proteomexchange.org/dataset/PXD041356).