Antibodies directed to the calmodulin-binding domain of B-50 (gap-43) inhibit Ca2+-induced dopamine release from permeated synaptosomes

✍ Scribed by Jacques J.H. Hens; Govert Hoogland; Pim J. French; Frans Boomsma; Pierre N. E. De Graan

• Book ID: 102661396
• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 658 KB
• Volume: 19
• Category: Article
• ISSN: 0893-6609
• DOI: 10.1002/(sici)1520-6769(199607)19:1<9::aid-nrc158>3.0.co;2-q

✦ Synopsis

is an atypical calmodulin-binding protein with a higher affinity for calmodulin in the absence than in the presence of Ca2+. In the mature synapse B-50 has been implicated in the release of noradrenaline and neuropeptide cholecystokinin-8. Using the cross-linker disuccinimidyl suberate we demonstrate in native syna tosomal plasma membranes that B-50 retains its ability to interact with calmodulin in a Ca!+-dependent manner at physiological salt concentrations. The importance of the calmodulin-binding domain and the protein kinase C phosphorylation site of B-50 in the regulation of neurotransmitter release was studied by introducing monoclonal anti-B-50 antibodies NM2 and NM6 into streptolysin-0-permeated synaptosomes. NM2 antibodies, which interfere with the calmodulin-binding and phosphorylation properties at the Nterminus of B-50, inhibited the endogenous, Ca2+-induced dopamine release from permeated synaptosomes, whereas NM6 antibodies directed to a C-terminal domain of B-50 were without effect. We conclude that the N-terminal domain of the B-50 protein plays an important role in the process of Ca2+-induced dopamine release, presumably by serving as a local calmodulin store which is regulated in a C$+-and phosphorylation-dependent fashion.