Subcellular distribution of neurabin immunolabeling in primate prefrontal cortex: comparison with spinophilin

Prefrontal cortical functioning depends on dopaminergic neurotransmission, which in turn depends on a complex signal transduction pathway including protein phosphatase-1 (PP1). Targeted localization of PP1 by the scaffolding proteins, spinophilin and neurabin, is critical for dopaminergic modulation of glutamate neurotransmission. In this study, we report the preparation of an antiserum to neurabin, use it to study the subcellular localization of neurabin and compare that to our previous study of spinophilin, a closely related PP1 scaffold. Neurabin is found predominately in dendritic spines, but is also found in other compartments, including dendrites, axons, terminals and glia. This distribution contrasts with that of spinophilin in that neurabin is found in axon terminals where spinophilin is absent, and in parvalbumin-containing interneuron dendrites there is no significant neurabin though these dendrites contain substantial spinophilin. Within the dendritic spine compartment, however, the two proteins are similarly distributed. Both neurabin and spinophilin are concentrated in spines, and double-labeling reveals that they co-localize in most spines. Furthermore, post-embedding immunogold labeling demonstrates that within a spine, neurabin is distributed in the same pattern as spinophilin, concentrated in the postsynaptic density and the 100 nm just below. These results indicate that neurabin and spinophilin share important similarities and differences in their patterns of distribution. Varying patterns of scaffold localization may play an important role in determining the content and action of signal transduction pathways in different neuronal populations or compartments.