Cloning and distribution analysis of Nav1.5 sodium channel in rat brain

To clarify the gene and molecule characters of the tetrodotoxin-resistant (TTX-R) voltage -gate sodium channel and the distribution in different lobe of brain in different developmental stage, reverse transcriptase-polymerase chain reaction (RT-PCR) was used to clone the full sequence of Nav1.5 sodium channel (designated as rN1) alpha, subunit in rat brains and the distribution was compared in different lobe of brain in different developmental stage. The open reading frame(ORF) of rN1 encodes 2016 amino acid residues and sequence analysis indicated that rN1 is highly homologous with 96.53% amino acids identity to rat cardiac Nav1.5 sodium channel (rH1) and 96.13% amino acids identity to human neuroblastoma Nav1.5 sodium channel (hNbR1). It has all the structural features of a voltage-gated sodium channel and the presence of a cysteine residue (C373) in the pore loop region of domain I suggests that this channel is TTX resistant. A new exon (exon7) that distinct from rN1 was found in D I -S3 similar to S4. In addition, an alternative splicing isoforms that deleted 53 amino acids(exon20) was found in the loop between D II similar to III in rN1 (designated as rN1-2). Distribution result demonstrated that rN1 expressed discrepancy in different ages and lobe in brain. The expression level of rN1 was gradually more stable in adult than neonatal. These results suggest that Nav1.5 has a newly identified exon for alternative splicing and is more widely expressed than previously thought.