125I-Labelled mapacalcine: a specific tool for a pharmacological approach to a receptor associated with a new calcium channel on mouse intestinal membranes.
Mapacalcine is a small protein (Mr=19041) composed of two homologous chains purified from the marine sponge Cliona vastifica. Recently, we demonstrated that it was able to specifically block a Ca2+ channel which could not be related to already described channels on mouse intestinal myocytes. This Ca2+ current was insensitive to the known peptidic and organic calcium channel blockers. Mapacalcine was ineffective on T-type and L-type Ca2+ currents present on rat portal vein myocytes [Morel, Drobecq, Sautière, Tartar, Mironneau, Qar, Lavie, and Hugues (1997) Mol. Pharmacol. 51, 1042-1052]. We report here the preparation and purification of a monoiodo-derivative of mapa-calcine which retains its biological properties. Binding parameters of mapacalcine to its receptors have been characterized on mouse intestinal membranes. It binds to its receptors with a Kd=0. 8 nM, and a maximal binding capacity of 171 fmol/mg of protein on membrane preparations. Our data show that we have prepared a tool that is usable for pharmacological studies of a receptor associated with a new type of calcium channel for which no ligand was available until now.
Vidalenc
P
P
Centre National de la Recherche Scientifique, ESA5017, Physiopathologie et Pharmacologie Vasculaire, Faculté de Pharmacie, Université Victor Segalen (Bordeaux 2), 146 rue Léo Saignat, 33076 Bordeaux Cedex, France.
Morel
J L
JL
Mironneau
J
J
Hugues
M
M
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000032:analysis*; D002462:Cell Membrane / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000648:ultrastructure; D007457:Iodine Radioisotopes; D051379:Mice; D011506:Proteins / Q000494:pharmacology*; D011869:Radioligand Assay; D051381:Rats; D011956:Receptors, Cell Surface / Q000032:analysis* / Q000037:antagonists & inhibitors
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D007457:Iodine Radioisotopes; D011506:Proteins; D011956:Receptors, Cell Surface; C106560:mapacalcine