1. Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, U.K.
2. Science for Life Laboratory, Division of Translational Medicine and Chemical Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 21 Stockholm, Sweden
3. Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Street 9b, D-50931 Köln/Cologne, Germany