SUBCELLULAR-LOCALIZATION OF 14-3-3-ISOFORMS IN RAT-BRAIN USING SPECIFIC ANTIBODIES

The 14-3-3 protein family, which is present at particularly high conce ntrations in mammalian brain, is known to be involved in various cellu lar functions, including protein kinase C regulation and exocytosis. D espite the fact that most of the 14-3-3 proteins are cytosolic, a smal l but significant proportion of 14-3-3 in brain is tightly and selecti vely associated with some membranes. Using a panel of isoform-specific antisera we find that the epsilon, eta, gamma, beta, and zeta isoform s are all present in purified synaptic membranes but absent from mitoc hondrial and myelin membranes. In addition, the eta, epsilon, and gamm a isoforms but not the beta and zeta isoforms are associated with isol ated synaptic junctions. When different populations of synaptosomes we re fractionated by a nonequilibrium Percoll gradient procedure, the ep silon and gamma isoforms were present and the beta and zeta isoforms w ere absent from the membranes of synaptosomes sedimenting in the more dense parts of the gradient. The finding that these proteins are assoc iated with different populations of synaptic membranes suggests that t hey are selectively expressed in different classes of neurones and rai ses the possibility that some or all of them may influence neurotransm ission by regulating exocytosis and/or phosphorylation.