[1] Univ Cologne, Fac Med, Inst Biochem 1, Ctr Mol Med, D-50931 Cologne, Germany
[2] Univ Cologne, Dept Dermatol, D-50931 Cologne, Germany
[3] Northwestern Univ, Feinberg Sch Med, Dept Med, Chicago, IL 60611 USA
[4] Univ Durham, Sch Biol & Biomed Sci, Dept Biol Sci, Durham DH1 3LE, England