Evidence for a role of calmodulin in calcium-induced noradrenaline release from permeated synaptosomes: effects of calmodulin antibodies and antagonists.
The nervous tissue-specific protein B-50 (GAP-43), which has been implicated in the regulation of neurotransmitter release, is a member of a family of atypical calmodulin-binding proteins. To investigate to what extent calmodulin and the interaction between B-50 and calmodulin are involved in the mechanism of Ca(2+)-induced noradrenaline release, we introduced polyclonal anti-calmodulin antibodies, calmodulin, and the calmodulin antagonists trifluoperazine, W-7, calmidazolium, and polymyxin B into streptolysin-O-permeated synaptosomes prepared from rat cerebral cortex. Anti-calmodulin antibodies, which inhibited Ca2+/calmodulin-dependent protein kinase II autophosphorylation and calcineurin phosphatase activity, decreased Ca(2+)-induced nor-adrenaline release from permeated synaptosomes. Exogenous calmodulin failed to modulate release, indicating that if calmodulin is required for vesicle fusion it is still present in sufficient amounts in permeated synaptosomes. Although trifluoperazine, W-7, and calmidazolium inhibited Ca(2+)-induced release, they also strongly increased basal release. Polymyxin B potently inhibited Ca(2+)-induced noradrenaline release without affecting basal release. It is interesting that polymyxin B was also the only antagonist affecting the interaction between B-50 and calmodulin, thus lending further support to the hypothesis that B-50 serves as a local Ca(2+)-sensitive calmodulin store underneath the plasma membrane in the mechanism of neurotransmitter release. We conclude that calmodulin plays an important role in vesicular noradrenaline release, probably by activating Ca2+/calmodulin-dependent enzymes involved in the regulation of one or more steps in the release mechanism.
Hens
J J
JJ
Department of Medical Pharmacology, Rudolf Magnus Institute for Neurosciences, Utrecht University, The Netherlands.
Oestreicher
A B
AB
De Wit
M
M
Marquart
A
A
Gispen
W H
WH
De Graan
P N
PN
D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000276:immunology / Q000494:pharmacology*; D019922:GAP-43 Protein; D007093:Imidazoles / Q000494:pharmacology; D007074:Immunoglobulin G / Q000276:immunology / Q000494:pharmacology; D008297:Male; D008562:Membrane Glycoproteins / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D010539:Permeability; D051381:Rats; D017208:Rats, Wistar; D013449:Sulfonamides / Q000494:pharmacology; D013574:Synaptosomes / Q000378:metabolism*; D014268:Trifluoperazine / Q000494:pharmacology
D000906:Antibodies; D002147:Calmodulin; D019922:GAP-43 Protein; D007093:Imidazoles; D007074:Immunoglobulin G; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D013449:Sulfonamides; D014268:Trifluoperazine; C031938:calmidazolium; C017967:W 7; D002118:Calcium; D009638:Norepinephrine