CREATINE-KINASE ISOENZYMES IN CHICKEN CEREBELLUM - SPECIFIC LOCALIZATION OF BRAIN-TYPE CREATINE-KINASE IN BERGMANN GLIAL-CELLS AND MUSCLE-TYPE CREATINE-KINASE IN PURKINJE NEURONS

Creatine kinase isoenzymes were localized in the chicken cerebellum by the use of isoenzyme-specific anti-chicken creatine kinase antibodies. Brain-type creatine kinase was found in high amounts in the molecular layer, particularly in Bergmann glial cells but also in other cells of the cerebellar cortex, e.g. in astrocytes and in the glomerular structures, as well as in cells of the deeper nuclei. A mitochondrial creatine kinase isoform was primarily localized to the glomerular structures in the granule cell layer and was also identified in Purkinje neurons. Surprisingly, a small amount of the muscle-type creatine kinase isoform was identified in cerebellar extracts by immunoprecipitation, immunoblotting and native enzyme electrophoresis, and was shown to be localized exclusively in Purkinje neurons. Cell type-specific expression of brain- and muscle-type creatine kinase in Bergmann glial cells and Purkinje neurons, respectively, may serve to adapt cellular ATP regeneration to the different energy requirements in these specialized cell types. The presence of brain-type creatine kinase in Bergmann glial cells and astrocytes is discussed within the context of the energy requirements for ion homeostasis (K+ resorption), as well as for metabolite and neurotransmitter trafficking. In addition, the presence of muscle-type creatine kinase in Purkinje neurons, which also express other muscle-specific proteins, is discussed with respect to the unique calcium metabolism of these neurons and their role in cerebellar motor learning.