We report here some results of a proteomic analysis of changes in
protein expression in the leech Hirudo medicinalis in response to septic injury. Comparison of two-dimensional
protein gels revealed several significant differences between normal and experimental tissues. One
protein found to be up-regulated after
septic shock was identified, through a combination of Edman degradation, mass spectrometry, and molecular cloning, as a novel member of the
hemerythrin family, a group of non-
heme-
iron oxygen transport proteins found in four invertebrate phyla: sipunculids, priapulids, brachiopods, and annelids. We found by in situ hybridization and immunocytochemistry that the new leech
protein, which we have called neurohemerythrin, is indeed expressed in the leech central nervous system. Both message and
protein were detected in the pair of large glia within the ganglionic neuropile, in the six packet glia that surround neuronal somata in each central
ganglion, and in the bilateral pair of glia that separate axonal fascicles in the interganglionic connective nerves. No expression was detected in central neurons or in central nervous system microglia. Expression was also observed in many other, non-neuronal tissues in the body wall. Real-time PCR experiments suggest that neurohemerythrin is up-regulated posttranscriptionaly. We consider potential roles of neurohemerythrin, associated with its ability to bind
oxygen and
iron, in the innate immune response of the leech nervous system to bacterial invasion.