Cellular and subcellular localization of a newly identified member of the protein 4.1 family, brain 4.1, in the cerebellum of adult and postnatally developing rats

For obtaining a deeper insight into the properties of a newly characterized member of the protein 4.1 family, brain 4.1, the cellular and subcellular localization was investigated in the cerebellar cortex of adult and postnat ally developing rats. Fluorescent immunohistochemical observations showed t hat brain 4.1 localized predominantly to glomeruli in the granular layer an d throughout the molecular layer in adult rat cerebellar cortex. Analysis o f subcellular localization of brain 4.1 by immune-electron microscopy furth er demonstrated that presynaptic terminals of mossy fibers and parallel fib ers, cytoplasm of granule cells and cytoplasm and/or processes of glial cel ls contained brain 4.1 while postsynaptic regions of the dendrites of granu le cells and Purkinje cells, axons and myelin sheaths did not. Thus, one of the major subcellular destination of brain 4.1 was presynaptic terminal in the cerebellum. This was further supported by the fact that the immunostai ning pattern of brain 4.1 in the cerebellum changed in a similar way to tha t of a synaptic terminal marker, synaptophysin during the postnatal develop ment. Immunoblot analysis also demonstrated that contents of brain 4.1 isof orms varied in parallel with the changes of the immunostaining pattern. Bio chemical analysis confirmed the presence of brain 4.1 at synaptic terminals , but there was no obvious correlation between each isoform and its subcell ular localization. These results suggested that brain 4.1 is involved in th e formation and maintenance of synapse as a membrane skeletal component at presynaptic terminals in the cerebellum. (C) 1999 Elsevier Science B.V. All rights reserved.