PROTEIN KINASE-C-DELTA IN RAT-BRAIN - ASSOCIATION WITH SENSORY NEURONAL HIERARCHIES

Originally characterized as the calcium- and phospholipid-dependent pr otein kinases, protein kinases C include at least eight separate isofo rms, some of which are calcium-independent and all of which are highly enriched in brain. Of the calcium-independent isoforms, the delta sub species of protein kinase C has the most restricted complement of lipi d activators and substrate specificity, suggesting that it may have a unique role in cell signalling pathways. Using immunocytochemistry, we report that the distribution of protein kinase C-delta immunoreactivi ty in rat brain is also restricted, being present in all sensory syste ms. Moreover, it is found in alternating hierarchies of sensory pathwa ys: in all sensory systems except auditory, it is found in first- and third-order neurons, while in the auditory system, it is found in seco nd- and fourth-order neurons. Thalamocortical systems are intensely im munoreactive, including barrel fields of the rat parietal cortex. Outs ide of sensory systems, protein kinase C-delta is present in cerebellu m within longitudinal stripes in Purkinje neurons, and in the caudate- putamen, it appears to be associated with the striosome (patch) compar tment. In contrast to all other protein kinase C isoforms, protein kin ase C-delta is absent from hippocampus. These findings suggest that pr otein kinase C-delta may have a unique role in signal transduction in the central nervous system (CNS), especially in sensory systems.