Characterization of synaptophysin and G proteins in synaptic vesicles and plasma membrane of Aplysia californica.
Two components of synaptic terminals that may be involved in transmitter release are synaptophysin (p38) and G proteins. In order to study release mechanisms in Aplysia californica we have prepared subcellular fractions from nervous tissue to characterize and localize these components. We identify Aplysia synaptophysin by Western blot analysis with monoclonal antibody SY38, find that it is enriched in synaptic vesicles, and, using immunocytochemistry, show that it is localized to neuropil. These characteristics indicate that Aplysia synaptophysin is closely related to mammalian synaptophysin; it appears to be much smaller, however, having a mass of 28 kDa instead of 38 kDa. We previously determined that G protein subunits in Aplysia are enriched in neuropil and synaptosomes. We now show that within the synaptic terminal the pertussis toxin-sensitive alpha-subunit as well as the beta-subunit are associated with plasma membrane using [32P]ADP-ribosylation and Western blotting with G protein-specific antibodies.
Chin
G J
GJ
Howard Hughes Medical Institute, Center for Neurobiology and Behavior, New York, NY 10032.
Vogel
S S
SS
Elste
A M
AM
Schwartz
J H
JH
D000818:Animals; D000911:Antibodies, Monoclonal; D001048:Aplysia / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000032:analysis*; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000032:analysis*; D008970:Molecular Weight; D013572:Synaptic Vesicles / Q000032:analysis*; D016708:Synaptophysin; D013574:Synaptosomes / Q000032:analysis
D000911:Antibodies, Monoclonal; D008565:Membrane Proteins; D016708:Synaptophysin; D019204:GTP-Binding Proteins