In order to validate the mass spectrometry discoveries, we cultured human FLS cell lines generated from patients with RA (20, 32) and used their cell lysates for immunoprecipitation with anti-HIP1 antibody, followed by Western blot with anti-COPE, anti-KIF1C, anti-TRIOBP, and anti-YWHAH. Here, KIF1C is linked to rheumatoid arthritis.