The invention provides a method of treating or preventing neurodegeneration in a subject in need thereof, which method comprises the step of administering to the subject a therapeutically effective amount of a polypeptide, or a polynucleotide encoding said polypeptide, wherein said polypeptide has the amino acid sequence shown in SEQ ID NO: 2, or an amino acid sequence having at least 90% homology to the amino acid sequence shown in SEQ ID NO: 2.