Cerebellin is a postsynaptic neuropeptide

Abstract

Cerebellin is a hexadecapeptide that has been biochemically characterized and localized to cerebellar Purkinje cells and certain neurons of the dorsal cochlear nucleus (DCoN) of rat. Among rabbit antisera produced to synthetic cerebellins, one (C₁) gave specific immunostaining of the Purkinje neuronal cell body, initial axon segment, and main stem dendrites, while another (R₂) reacted with peripheral dendritic structures. This complementarity of staining was also present during cerebellar development. By electron microscopy, the immunoreaction product was localized to polyribosomal domains with antiserum C₁ and to dendritic spines with antiserum R₂, in both cerebellar cortex and DCoN. In the spine, the structure most strongly stained was the postsynaptic density, but some reaction product was adsorbed to the plasma membrane, the spine apparatus, and the granulofibrillar cytoplasmic component. Antiserum R₂ also stained lysosome-like bodies. We suggest that antiserum C₁ recognizes cerebellin precursor(s) and antiserum R₂ mature peptide(s) and perhaps degradation product. There is structural homology between cerebellin and residues 625–641 of the polyimmunoglobulin transporter. The functional implications of this homology and other possible roles of cerebellin are discussed.