Calcium/calmodulin inhibits the binding of specific [125I]omega-conotoxin GVIA to chick brain membranes.
The effect of Ca2+/calmodulin (CaM) on the specific binding of [125I]omega-conotoxin GVIA (125I-omega-CTX) to crude membranes from chick brain was investigated. When we examined the effects of the activation of various endogenous protein kinases on specific [125I]omega-CTX binding to crude membranes, we observed that Ca2+/CaM had an inhibitory effect regardless of whether or not the standard medium contained ATP (0.5 mM). Ca2+/CaM also had an inhibitory effect in a simple binding-assay medium containing HEPES-HCl buffer, BSA, Ca2+ and CaM, and this effect was dependent on the concentration of Ca2+. The effect of Ca2+/CaM was attenuated by the CaM antagonists W-7 and CaM-kinase II fragment (290-309). An experiment with modified ELISA using purified anti omega-CTX antibody indicated that Ca2+/CaM did not affect the direct binding of [125I]omega-CTX and CaM. These results suggest that Ca2+/CaM either directly or indirectly affects specific [125I]omega-CTX binding sites, probably N-type Ca2+ channels in crude membranes from chick whole brain.
Ichida
S
S
Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Kinki University, Higashi-Osaka, Japan. seiji@phar.kindai.ac.jp
Abe
J
J
Yu-an
Z
Z
Sugihara
K
K
Imoto
K
K
Wada
T
T
Sohma
H
H
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000378:metabolism*; D020864:Calcium Channels, N-Type / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D002645:Chickens; D004797:Enzyme-Linked Immunosorbent Assay; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D008566:Membranes; D020866:omega-Conotoxin GVIA / Q000378:metabolism*
D002121:Calcium Channel Blockers; D020864:Calcium Channels, N-Type; D002147:Calmodulin; D007457:Iodine Radioisotopes; D020866:omega-Conotoxin GVIA; D002118:Calcium