NEUROPATHY TARGET ESTERASE - IMMUNOLOCALIZATION TO NEURONAL CELL-BODIES AND AXONS

Determination of the molecular mechanisms involved in organophosphate- induced axonopathy may help to elucidate those involved in normal axon al maintenance and in other neurodegenerative conditions. In this stud y we aimed to define the cellular distribution of neuropathy target es terase, the primary target protein for neuropathic organophosphates. A synthetic peptide corresponding to the sequence of a proteolytic frag ment of neuropathy target esterase purified from chicken brain was use d to raise a rabbit antiserum designated R28. The antiserum was shown by immunoprecipitation and western blotting of brain extracts to react with a polypeptide of the expected molecular size (155,000 mel. wt); this reaction was blocked by preincubating the antiserum with the immu nizing peptide. Prominent intracellular immunostaining by R28 was seen in neuronal cell bodies and, in some cases, proximal axon segments in frozen sections of chicken brain cortex, optic tectum, cerebellum, sp inal cord, and dorsal root ganglia. Cells with glial morphology were n ot immunostained, neither were normal sciatic nerve or motor end plate s. However, 8-12 h following sciatic nerve ligation, immunoreactive ma terial was seen to accumulate both proximal and, to a lesser extent, d istal to the ligature, indicating that neuropathy target esterase unde rgoes fast axonal transport. No gross qualitative or quantitative chan ges in the above pattern of neuropathy target esterase immunoreactivit y were detected in tissue obtained from chickens one or three days fol lowing treatment with a neuropathic organophosphate. The presence of n europathy target esterase in essentially all neurons indicates that th e selective vulnerability of long axons to neuropathic organophosphate s is dependent on factors additional to the presence of the target pro tein. (C) 1997 IBRO. Published by Elsevier Science.