RT Journal Article SR Electronic T1 Purification of a New Dimeric Protein from Cliona vastifica Sponge, which Specifically Blocks a Non-L-Type Calcium Channel in Mouse Duodenal Myocytes JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 1042 OP 1052 DO 10.1124/mol.51.6.1042 VO 51 IS 6 A1 Jean-Luc Morel A1 Hervé Drobecq A1 Pierre Sautiere A1 André Tartar A1 Jean Mironneau A1 Janti Qar A1 Jean-Louis Lavie A1 Michel Hugues YR 1997 UL http://molpharm.aspetjournals.org/content/51/6/1042.abstract AB Marine sponges are synthesizing a wide variety of peptidic and organic molecules with biological activities. Multiple-step purification ofCliona vastifica extract led to a new dimeric peptide (mapacalcine; M r = 19,064) that is composed of two homologous chains, each containing nine cysteins. This protein has been found to selectively block a new calcium conductance characterized in mouse duodenal myocytes with an IC50 value of ∼0.2 μm. The mapacalcine-sensitive current was a non-L-type calcium current activated from a holding potential of −80 mV that persisted during stimulation of the cell at high frequencies (0.1–0.2 Hz) within 5–10 min. Time constants of inactivation were similar for both L-type and non-L-type calcium currents. The non-L-type calcium current of duodenal myocytes was not blocked by the pharmacological agents specific for N-, L-, P-, or Q-type calcium channels. Mapacalcine was unable to block T-type calcium current in portal vein myocytes as well as voltage-dependent potassium currents and calcium-activated chloride currents in duodenal and portal vein cells. Mapacalcine did not affect caffeine-induced calcium responses, indicating that it did not interfere with intracellular calcium stores. Competition experiments on mouse intestinal membranes showed that mapacalcine did not interact with dihydropyridines receptors. These data suggest that mapacalcine may be a specific inhibitor of a new type of calcium current, first identified in duodenal myocytes.