CLONING AND TISSUE DISTRIBUTION OF THE APLYSIA NA-SUBUNIT CDNA( CHANNEL ALPHA)

Voltage-gated Na+ channels generate the depolarizing inward current th at is critical for the initiation and conduction of action potentials. To study the roles of Na+ channels in neuronal signaling, we have beg un the molecular analysis of Na+ channels in Aplysia californica. We h ave isolated cDNAs that encode a neuronal Na+ channel alpha-subunit, w hich we have named SCAP1. DNA sequence analysis of the SCAP1 cDNA reve aled an open reading frame that predicts a protein of 1,993 amino acid s, which is highly similar to other members of the Na+ channel alpha-s ubunit gene family. RNase protection assays carried out on various Apl ysia tissues indicated that SCAP1 is expressed predominantly in the ne rvous system. All of the nonneuronal tissues tested were negative with the exceptions that low levels of expression were observed in ovotest is and parapodium, probably due to the presence of small numbers of ne urons within these tissue preparations. Southern blot hybridization at reduced stringency indicated that the genome of Aplysia contains more than one Na+ channel alpha-subunit gene.