α 1 and α 2 Ca 2+ channel subunit expression in human neuronal and small cell carcinoma cells

Monoclonal antibodies that recognize skeletal muscle dihydropyridine‐sensitive calcium channel subunits were used to identify similar proteins in neuronal and small cell carcinoma cell lines. α 1 ‐related proteins were detected by FACS analysis on the surface of human neuroblastoma (IMR 32) and small cell carcinoma (DMS 273 and DMS 114) cell lines. α 1 ‐like polypeptides from these cells were isolated and partially characterized. The polypeptides exhibit an M r similar to that of the L‐type channel α 1 subunit and are recognized by two distinct anti‐ α1 mAbs. The data provide biochemical evidence for structural similarities between the α 1 sub‐unit of small cell carcinoma and neuronal cell lines. Similarly, an α 2 ‐like protein was characterized from these cells. Because α 2 is a subunit shared by many subtypes of calcium channels, these data suggest that subunits other than the pore‐forming α 1 subunit may play an important role in the etiology of Lambert‐Eaton syndrome. We demonstrate directly that small cell carcinoma and a cell line derived from peripheral neurons share L‐type calcium channel‐related proteins and a protein common to many voltage‐gated calcium channel subtypes. These data support a model that proposes that cross‐reactivity of anti‐tumor cell antibodies with presynaptic elements, possibly calcium channels, plays a role in the development of Lambert‐Eaton syndrome.— Morton, M. E., Cassidy, T. N., Froehner, S. C., Gilmour, B. P., Laurens, R. L. α 1 and α 2 Ca 2+ channel subunit expression in human neuronal and small cell carcinoma cells. FASEB J. 8: 884‐888; 1994.