HOT-SPOTS OF CREATINE-KINASE LOCALIZATION IN BRAIN - CEREBELLUM, HIPPOCAMPUS AND CHOROID-PLEXUS

Creatine kinase (CK) isoenzymes, with emphasis on the mitochondrial CK isoenzymes, were characterized and localized in chicken cerebellum. C hicken cerebellar extracts analyzed by two-dimensional gels, using ant ipeptide antibodies specific for sarcomeric muscle-type mitochondrial CK (Mi(b)-CK) and revealed the presence of a Mi(b)-CK variant in avian cerebellum, This CK isoform was localized by immunofluorescence stain ing exclusively in the Purkinje neurons. The co-expression of this Mi( b)-CK together with cytosolic muscle-type MM-CK, as observed in the sa me Purkinje neurons, may reflect the specific energy requirements asso ciated with highly fluctuating Ca2+ levels (Ca2+ spiking) in these spe cialized neurons. Ubiquitous brain-type mitochondrial Mi(a)-CK was fou nd together with cytosolic BB-CK mainly in the glomeruli structures of the cerebellar granular layer. BB-CK, but much less so Mi(a)-CK, howe ver, was also very prominent in Bergmann glial cells of the molecular layer. Thus, an isoenzyme-specific differential localization of the tw o mitochondrial MI-CK isoenzymes in the chicken cerebellum is demonstr ated. Other hot spots of CK localization were the granule and pyramida l cells of the hippocampus in rat. There, a developmental stage-depend ent immunofluorescence staining, especially with antibodies against Mi (a)-CK, was noted. Epithelial cells of the choroid plexus were also hi ghly enriched in CK, The possible implications of a CK/PCr circuit at these various cellular locations of the brain are discussed with respe ct to normal brain physiology and pathology.