Cysteine proteinases in rat dorsal root ganglion and spinal cord, with special reference to the co-localization of these enzymes with calcitonin gene-related peptide in lysosomes.

To examine the localization of lysosomal cysteine proteinases, cathepsins B, H, and L, and their correlation with a neuropeptide, calcitonin gene-related peptide (CGRP) in nerve cells, immunocytochemistry was applied to rat dorsal root ganglion (DRG) and spinal cord (SC) of lumbar segments. By light microscopy, granular immunodeposits for cathepsins B and L were localized in small and large nerve cells in DRG and SC. The cathepsin B- and L-positive smaller nerve cells in DRG and large nerve cells in the ventral horn of SC were also immunostained by anti-CGRP. By electron microscopy, nerve cells in DRG and SC contained lysosomes labeled by immunogold particles indicating cathepsins B and L, while immunogold particles for cathepsin L labeled lysosomes of glial cells. Double immunostaining co-localized immunogold particles for cathepsin B or L and CGRP in lysosomes of small nerve cells in DRG and motoneurons in SC. Moreover, cathepsin H was immunocytochemically demonstrated in lysosomes of satellite cells in DRG, while lysosomes of perivascular microglia-like cells were labeled by immunogold particles for cathepsins B, H, and L. The results suggest the possibility that lysosomes in nerve cells participate in regulation of intraneuronal CGRP level by degrading CGRP.