EVIDENCE FOR AN ENDOGENOUS NEUROCIDIN IN THE MANDUCA-SEXTA VENTRAL NERVE CORD

Half of the neurons in the abdominal nervous system of the moth Manduc a sexta die after adult eclosion. Two physiological signals regulate p ost-eclosion neuronal death in adult moths. The first is endocrine: a decline in blood ecdysteroids is necessary for the death of neurons in the segmental ganglia. The second signal, which is highly specific fo r a pair of motoneurons found at the posterior midline in each of the three unfused abdominal ganglia, originates in the nervous system. It is transmitted from the fused pterothoracic ganglion to abdominal gang lion A3 via the intersegmental connectives. To characterize the signal of neural origin, we have developed an in vitro bioassay for neuron-k illing factors (''neurocidins''). Aqueous extracts of pterothoracic ga nglia were prepared and applied to cultured ventral nerve cords. These extracts exhibited concentration-dependent effectiveness in killing m otoneurons. The active component of the extract was heat-stable and pr otease-sensitive. Size fractionation studies suggested that the active component has a molecular mass between 10 and 30 kD. This is the firs t report of an endogenous neuron-killing protein from an insect nervou s system. (C) 1995 Wiley-Liss, Inc.