Molecular Characterization of Voltage-Gated Sodium Channels and Their Relations with Paralytic Shellfish Toxin Bioaccumulation in the Pacific Oyster Crassostrea gigas.

Paralytic shellfish toxins (PST) bind to voltage-gated sodium channels (Nav) and block conduction of action potential in excitable cells. This study aimed to (i) characterize Nav sequences in and (ii) investigate a putative relation between Nav and PST-bioaccumulation in oysters. The phylogenetic analysis highlighted two types of Nav in : a Nav1 () and a Nav2 () with sequence properties of sodium-selective and sodium/calcium-selective channels, respectively. Three alternative splice transcripts of named A, B and C, were characterized. The expression of , analyzed by in situ hybridization, is specific to nervous cells and to structures corresponding to neuromuscular junctions. Real-time PCR analyses showed a strong expression of in the striated muscle while is mainly expressed in visceral ganglia. expression is ubiquitous. The PST binding site (domain II) of variants possess an amino acid Q that could potentially confer a partial saxitoxin (STX)-resistance to the channel. The genotype or alternative splicing would not be the key point determining PST bioaccumulation level in oysters.