Journal of Neuroscience, Vol 2, 1692-1704, Copyright © 1982 by Society for Neuroscience
Characterization and localization of adenosine 3':5'-monophosphate- binding proteins in the nervous system of Aplysia
CM Eppler, MJ Palazzolo and JH Schwartz
Earlier work in Aplysia californica has indicated that sensitization of the
gill reflex, a simple form of learning, is produced by cAMP- dependent
protein phosphorylation which regulates the flux of ions in sensory neurons
of the abdominal ganglion. These changes in ion flux result in the enhanced
release of neurotransmitter from synapses of the sensory neurons which, in
turn, mediate the behavior. Because it can be presumed that protein
phosphorylation regulates the functioning of ion channel proteins, we have
characterized cAMP-binding proteins photoaffinity labeled with 8-N3-cAMP
and have found that, unlike other tissues, the nervous system contains a
great variety of binding species. Also unlike other tissues, several of the
binding proteins in neurons are associated with membrane, and these
components are concentrated in fractions enriched in nerve endings.
Selectivity of phosphorylation, not only between substrates in cytosol and
membrane but also between different regions of the cell, is thus possible
because of the variety of cAMP-binding proteins in neurons. We think that
these membrane-associated binding proteins are the most likely candidates
for the regulatory subunits of the cAMP-dependent kinases that control the
functioning of ion channel proteins at the synapse.