Effect of N,N'-dicyclohexylcarbodiimide on acetylcholine release from Torpedo synaptosomes and proteoliposomes reconstituted with the proteolipid mediatophore.
The mediatophore is a presynaptic membrane protein that has been shown to translocate acetylcholine (ACh) under calcium stimulation when reconstituted into artificial membranes. The mediatophore subunit, a 15-kDa proteolipid, presents a very high sequence homology with the N,N'-dicyclohexylcarbodiimide (DCCD)-binding proteolipid subunit of the vacuolar-type H(+)-ATPase. This prompted us to study the effect of DCCD, a potent blocker of proton translocation, on calcium-dependent ACh release. The present work shows that DCCD has no effect on ACh translocation either from Torpedo synaptosomes or from proteoliposomes reconstituted with purified mediatophore. However, using [14C]DCCD, we were able to demonstrate that the drug does bind to the 15-kDa proteolipid subunit of the mediatophore. These results suggest that although the 15-kDa proteolipid subunits of the mediatophore and the vacuolar H(+)-ATPase may be identical, different domains of these proteins are involved in proton translocation and calcium-dependent ACh release and that the two proteins have a different membrane organization.
Sbia
M
M
Département de Neurochimie, CNRS, Gif sur Yvette, France.
Diebler
M F
MF
Morel
N
N
Israël
M
M
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D004024:Dicyclohexylcarbodiimide / Q000378:metabolism / Q000494:pharmacology*; D009411:Nerve Endings / Q000378:metabolism; D009419:Nerve Tissue Proteins; D011510:Proteolipids / Q000378:metabolism*; D013570:Synaptic Membranes / Q000378:metabolism; D013572:Synaptic Vesicles / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism*; D014101:Torpedo / Q000378:metabolism*
D009419:Nerve Tissue Proteins; D011510:Proteolipids; C050299:mediatophore; C020485:proteoliposomes; D004024:Dicyclohexylcarbodiimide; D000109:Acetylcholine