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

Overlapping cDNA clones spanning the entire coding region of a Na-chan nel alpha subunit were isolated from cultured Schwann cells from rabbi ts, The coding region predicts a polypeptide (Na-s) of 1984 amino acid s exhibiting several features characteristic of Na-channel alpha subun its isolated from other tissues, Sequence comparisons showed that the Na-s alpha subunit resembles most the family of Na channels isolated f rom brain (approximate to 80% amino acid identity) and is least simila r (approximate to 55% amino acid identity) to the atypical Na channel expressed in human heart and the partial rat cDNA, Nac, As for the bra in II and III isoforms, two variants of Na-s exist that appear to aris e by alternative splicing, The results of reverse transcriptase-polyme rase chain reaction experiments suggest that expression of Na-s transc ripts is restricted to cells in the peripheral and central nervous sys tems, Expression was detected in cultured Schwann cells, sciatic nerve , brain, and spinal cord but not in skeletal or cardiac muscle, liver, kidney, or lung.