A neuron regulatory factor (NRF), derived from cells of the central nervous system, is provided. A cytoprotective peptide (CPP) component of NRF is also provided, as are methods of using NRF or its CPP component. NRF comprises a large polypeptide or complex of polypeptides that is distinct from several other known neurotrophic or neuron regulatory factors. The CPP component of NRF is an acidic protein or protein complex whose amino acid sequence is unique among known protein sequences. Both NRF and its CPP component are capable of promoting survival and neurite outgrowth of cultured neurons in vitro, and preventing neuron degeneration and promoting neuron survival in vivo. The CPP component of NRF also exhibits a cytoprotective effect on non-neuronal cells.