Low prevalence of autoantibodies to CENP-H, -I, -K, -L, -M, -N, -T and -U in a Japanese cohort of anti-centromere positive samples

Objective: The constituents of the centromere region, centromere protein (CENP)-A, -B, and -C, are mainly targeted by anticentromere antibodies (ACA). Many other proteins also assemble around CENP-A nucleosomes in interphase nuclei to form the interphase centromere complex (ICEN). CENP-H, -I, -K, -L, -M, -N, -T, and -U have been reported as the constitutive components of ICEN. In this study, we examined the reactivities of ACA to the 8 CENPs for the purpose of investigating their autoantigenicity. Methods: Sera from 95 patients with ACA were tested by western blotting (WB) and enzyme-linked immunosorbent assay (ELISA) with the recombinant C-terminal of CENP-B (Ct-CENP-B). Next, the sera were examined for autoantibodies against the 8 CENPs by WB with each recombinant protein. Furthermore, the coiled-coil motifs and granzyme B (GB) cleavage for various CENPs were analyzed with computer tools. Results: Out of 95 ACA-positive sera, 85 and 93 sera were positive for anti-Ct-CENP-B antibodies in WB and in ELISA, respectively. In WB using the 8 CENPs, no sera reacted to any other 7 CENPs, except 1 serum, which reacted weakly to CENP-T. We were unable to find any obvious relationships between the autoantigenicity of CENPs and coiled-coil-forming probabilities or potential substrates for GB. Conclusion: This study demonstrates that ACA rarely target the 8 CENPs, in contrast to CENP-B. Protein structures might not contribute in a major way to the autoantigenicity of CENPs.