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 molecula r layer, particularly in Bergmann glial cells but also in other cells of the cerebellar cortex, e.g. in astrocytes and in the glomerular str uctures, as well as in cells of the deeper nuclei. A mitochondrial cre atine kinase isoform was primarily localized to the glomerular structu res in the granule cell layer and was also identified in Purkinje neur ons. Surprisingly, a small amount of the muscle-type creatine kinase i soform was identified in cerebellar extracts by immunoprecipitation, i mmunoblotting and native enzyme electrophoresis, and was shown to be l ocalized exclusively in Purkinje neurons. Cell type-specific expressio n of brain- and muscle-type creatine kinase in Bergmann glial cells an d Purkinje neurons, respectively, may serve to adapt cellular ATP rege neration to the different energy requirements in these specialized cel l types. The presence of brain-type creatine kinase in Bergmann glial cells and astrocytes is discussed within the context of the energy req uirements for ion homeostasis (K+ resorption), as well as for metaboli te and neurotransmitter trafficking. In addition, the presence of musc le-type creatine kinase in Purkinje neurons, which also express other muscle-specific proteins, is discussed with respect to the unique calc ium metabolism of these neurons and their role in cerebellar motor lea rning.