Neuropoietin is a newly identified member of the IL-6 cytokine family. Members of this family, including IL-6, IL-11, oncostatin M, leukemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), cardiotrophin-like cytokine, and CNTF, display a four-helix bundle structure, and signal through gp130-containing receptor complexes. Neuropoietin, which is predominantly expressed in neuroepithelia during embryonic life, acts through a receptor complex comprising CNTF receptor-a component, gp 130, and LIF receptor. Like CNTF, it promotes the survival of embryonic motor neurons and could increase the proliferation of neural precursor cells in the presence of EGF and FGF-2. Interestingly, the human Neuropoietin gene has evolved toward a pseudogene, suggesting that the alternative signaling via CNTF is an effective compensatory pathway. Recombinant murine Neuropoietin is a 19.8 kDa protein containing 183 amino acid residues.
