Neurone-specific enolase is a molecular marker for peripheral and central neuroendocrine cells

Abstract

NEURONE-SPECIFIC ENOLASE (NSE) is the most acidic brain isoenzyme of the glycolytic enzyme enolase (EC4.2.1.11) and has been shown to be homologous to the 14-3-2 protein isolated from bovine brain by Moore^1–3. Whereas NSE is exclusively localised in neurones in mammalian nervous tissue^4,5, another brain enolase isoenzyme termed non-neuronal enolase (NNE) is localised in glial elements⁵. As NSE and NNE are structurally, functionally and immunologically distinct isoenzymes that represent separate gene products^6,7, they are useful markers for cell classes in the nervous system. Although NNE is probably identical to liver enolase, NSE has to date been considered to be localised in neurones. We now report that NSE is also present in peripheral and central neuroendocrine cells, also termed amine precursor uptake and decarboxylation (APUD) cells^8–10. Immunocytochemistry using the unlabelled antibody enzyme method of Sternberger¹¹ demonstrates that APUD cells in both laboratory rat and rhesus monkey (Macacca mulatta) stain positively with NSE antiserum. Using a sensitive radioimmunoassay (RIA) for NSE, it is possible to confirm their localisation in adrenal gland and to support the finding in other APUD-cell-containing tissues in rat, monkey and man. The results in human tissues suggest that the immunocytochemical localisation in rat and monkey will be valid for man and prove useful in the study of human diseases involving the APUD cell class.