EXPRESSION OF A SINGLE-GENE PRODUCES BOTH FORMS OF SKELETAL-MUSCLE CYCLIC NUCLEOTIDE-GATED CHANNELS

Cyclic nucleotide-gated cation channels in skeletal muscle are respons ible for insulin-activated sodium entry into this tissue (J. E. M. McG eoch and G. Guidotti. J. Biol. Chem. 267: 832-841, 1992). These channe ls have previously been isolated from rabbit skeletal muscle by 8-brom oguanosine 3',5'-cyclic monophosphate (8-BrcGMP) affinity chromatograp hy, which separates them into two populations differing in nucleotide affinity [L. C. Santy and G. Guidotti. Am. J. Physiol. 271 (Endocrinol . Metab. 34): E1051-E1060, 1996]. In this study, a polymerase chain re action approach was used to identify skeletal muscle cyclic nucleotide -gated channel cDNAs. Rabbit skeletal muscle expresses the same cyclic nucleotide-gated channel as rabbit aorta (M. Biel, W. Altenhofen, R. Hullin, J. Ludwig, M. Freichel, V. Flockerzi, N. Dascal, U. B. Kaupp, and F. Hofmann. FEBS Lett. 329: 134-138, 1993). The entire cDNA for th is gene was cloned from rabbit skeletal muscle and an antiserum to thi s protein produced. Expression of this cDNA produces a 63-kDa protein with cyclic nucleotide-gated channel activity. A similarly sized immun oreactive protein is present in sarcolemma. Purification of the expres sed channels reveals that this single gene produces both native skelet al muscle channel populations.