IDENTIFICATION OF A SURVIVAL-PROMOTING PEPTIDE IN MEDIUM CONDITIONED BY OXIDATIVELY STRESSED CELL-LINES OF NERVOUS-SYSTEM ORIGIN

A survival-promoting peptide has been purified from medium conditioned by Y79 human retinoblastoma cells and a mouse hippocampal cell line ( HN 33.1) exposed to H2O2. A 30 residue synthetic peptide was made on t he basis of N-terminal sequences obtained during purification, and it was found to exhibit gel mobility and staining properties similar to t he purified molecules, The peptide maintains cells and their processes in vitro for the HN 33.1 cell line treated with H2O2, and in vivo for cortical neurons after lesions of the cerebral cortex. It has weak ho mology with a fragment of a putative bacterial antigen and, like that molecule, binds IgG, The peptide also contains a motif reminiscent of a critical sequence in the catalytic region of calcineurin-type phosph atases; surprisingly, like several members of this family, the peptide catalyzes the hydrolysis of para-nitrophenylphosphate in the presence of Mn2+. Application of the peptide to one side of bilateral cerebral cortex lesions centered on area 2 in rats results in an increase in I gG immunoreactivity in the vicinity of the lesions 7 d after surgery. Microglia immunopositive for IgG and ED-1 are, however, dramatically r educed around the lesions in the treated hemisphere. Furthermore, pyra midal neurons that would normally shrink, die, or disintegrate were ma intained, as determined by MAP2 immunocytochemistry and Nissl staining . These survival effects were often found in both hemispheres. The res ults suggest that this peptide operates by diffusion to regulate the i mmune response and thereby rescue neurons that would usually degenerat e after cortical lesions. The phosphatase activity of this molecule al so suggests the potential for direct neuron survival-promoting effects ,