Expression of endothelin-converting enzyme in both neuroblastoma and glial cell lines and its localization in rat hippocampus.

Endothelin-converting enzyme is a phosphoramidon-sensitive metalloprotease that cleaves big endothelin to the potent vasoconstrictor peptide, endothelin. The converting enzyme is expressed in endothelial cells in a variety of tissues and in some secretory cells. In the present study, phosphoramidon-sensitive endothelin-converting enzyme activity has been demonstrated by radioimmunoassay in the neuroblastoma cell line, SH-SY5Y, and in Bu17 and C6 glioma lines. The identity of the activity was confirmed by immunoblotting, revealing a polypeptide of approximately 120 kDa in each of these lines, in D384 glioma cells, and in primary astrocytes. Immunofluorescence revealed the cell-surface location of endothelin-converting enzyme in the neuronal and glial cell lines and in primary astrocytes. Pretreatment of SH-SY5Y and Bu17 cells with phosphoramidon resulted in an apparent concentration of the enzyme protein in an intracellular compartment. Immunoperoxidase-staining of rat brain sections located this metalloprotease to the pyramidal cells of the hippocampus. Endothelin-converting enzyme-1 was revealed by in situ hybridisation in the neuronal and glial cell lines.