Quantitative proteomics analysis of zebrafish exposed to sub-lethal dosages of β-methyl-amino-L-alanine (BMAA)

Abstract

The non-protein amino acid β-methylamino-L-alanine (BMAA) is a neurotoxin present in microalgae and shown to accumulate in the food web. BMAA has been linked to the complex neurodegenerative disorder of Guam and to increased incidents sporadic ALS. Two main neurotoxic routes are suggested; an excitotoxic by acting as an agonist towards glutamate receptors and a metabolic by misincorporating into cellular proteins. We have used zebrafish, an increasingly used model for neurodegenerative diseases, to further identify signaling components involved in BMAA-induced toxicity. Zebrafish embryos were exposed to sub-lethal dosages of BMAA and a label-free proteomics analysis was conducted on larvae 4 days post fertilization. The exposed larvae showed no developmental abnormalities, but a reduced heart rate and increased expression of GSK3 isoforms. Search towards a reviewed database containing 2968 entries identified 480 proteins. Only 17 of these were regulated 2-fold or more in the exposed larvae. Seven of these proteins could be associated to glutamate receptor signaling and recycling. The remaining nine have all been linked to disturbance in protein homeostasis, reactive oxygen species (ROS) development or neuronal cell death. We also found that BMAA influenced the endocannabinoid system by up-regulation of fatty acid amide hydrolase (FAAH) and that FAAH inhibitor URB597 reduced the BMAA effect on heart rate and GSK3 expression.

Exposure to BMAA mirrors molecular processes linked to neurodegenerative disease

“…The functions encompassed by the UPR include: (i) increased expression of folding chaperones to assist in proper protein folding, (ii) attenuation of translation, and (iii) activation of cellular apoptosis machinery in the event of irreversible ER stress . Activation of the UPR due to BMAA exposure has previously been described in exposed zebrafish by Frøyset and coworkers .…”

Zebrafish models in neuropsychopharmacology and CNS drug discovery

“…Pericardiac injection of BMAA during embryonic development alters protein homeostasis and glutamate signalling, whereas fish exposed to a sublethal dose of BMAA display reduced heart rate and abnormal spinal axis formation, but can be rescued pharmacologically (e.g. by inhibiting the endocannabinoid enzyme fatty acid amide hydrolase) (Purdie et al, ; Froyset et al, ).…”

Zebrafish as a Vertebrate Model System to Evaluate Effects of Environmental Toxicants on Cardiac Development and Function

“…Gene expression profiling using a small zebrafish sample has become possible due to recent advances in technology such as next-generation sequencing and RNA-seq [52,53,54]. Proteomics is also used in zebrafish toxicology research [55]. …”