Lambert-Eaton myasthenic syndrome immunoglobulins react with multiple types of calcium channels in small-cell lung carcinoma.
Barium currents through voltage-gated calcium (Ca2+) channels were studied in the small-cell lung carcinoma cell line NCI-H345 using patch clamp techniques. Pharmacological dissection of whole-cell barium currents revealed that 23% of the current was sensitive to nitrendipine, 35% to omega-conotoxin GVIA, and between 10 and 39% to omega-Aga-IVA. This implies that these cells express L-, N-, and P-type calcium channels. Only large cells expressed current that was sensitive to omega-Aga-IVA. The size dependency of this P-type channel expression may reflect the cell cycle stage. Cell-attached recordings revealed three unitary conductances: 5 to 6 pS, 10 to 12 pS, and 20 to 23 pS. The largest conductance channel (20-23 pS) was sensitive to Bay K 8644 and is presumed to represent L-type calcium channels. The frequency of observing the medium conductance channel (10-12 pS) was reduced by exposure to omega-conotoxin GVIA and may represent N-type channels. Incubation of cells with Lambert-Eaton myasthenic syndrome IgG for 24 to 48 hours removed up to 71% of the whole-cell current. Incubation with control human IgG (normal or myasthenia gravis) had no effect. Lambert-Eaton myasthenic syndrome IgG did not selectively target one "presynaptic" type of calcium channel, but rather appeared to target many of the calcium channel types that are expressed on small-cell lung carcinoma cells.
Meriney
S D
SD
Department of Neuroscience, University of Pittsburgh, PA 15260, USA.
Hulsizer
S C
SC
Lennon
V A
VA
Grinnell
A D
AD
D001323:Autoantibodies / Q000097:blood*; D001464:Barium / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000276:immunology / Q000502:physiology*; D018288:Carcinoma, Small Cell; D002453:Cell Cycle; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D006801:Humans; D015624:Lambert-Eaton Myasthenic Syndrome / Q000276:immunology*; D008175:Lung Neoplasms; D008564:Membrane Potentials / Q000187:drug effects; D009568:Nitrendipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D013111:Spider Venoms / Q000494:pharmacology; D020867:omega-Agatoxin IVA; D020866:omega-Conotoxin GVIA
D001323:Autoantibodies; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D010455:Peptides; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; D001464:Barium; D020866:omega-Conotoxin GVIA; D009568:Nitrendipine