CLONING OF A SODIUM-CHANNEL ALPHA-SUBUNIT FROM RABBIT SCHWANN-CELLS

Overlapping cDNA clones spanning the entire coding region of a Na-channel alpha subunit were isolated from cultured Schwann cells from rabbits, The coding region predicts a polypeptide (Na-s) of 1984 amino acids exhibiting several features characteristic of Na-channel alpha subunits isolated from other tissues, Sequence comparisons showed that the Na-s alpha subunit resembles most the family of Na channels isolated from brain (approximate to 80% amino acid identity) and is least similar (approximate to 55% amino acid identity) to the atypical Na channel expressed in human heart and the partial rat cDNA, Nac, As for the brain II and III isoforms, two variants of Na-s exist that appear to arise by alternative splicing, The results of reverse transcriptase-polymerase chain reaction experiments suggest that expression of Na-s transcripts is restricted to cells in the peripheral and central nervous systems, Expression was detected in cultured Schwann cells, sciatic nerve, brain, and spinal cord but not in skeletal or cardiac muscle, liver, kidney, or lung.