1. The Netherlands Cancer Institute 1 Division of Cell Biology I , , Plesmanlaan 121, Amsterdam 1066 CX , The Netherlands
2. The Netherlands Cancer Institute 2 Proteomics Facility , , Amsterdam 1066 CX , The Netherlands
3. Max Planck Institute of Biochemistry 3 Department of Molecular Medicine , , Am Klopfespitz 18, 82152 Martinsried , Germany