Anti-FZR1 monoclonal antibody, clone BS49.3

Background: Although the mitotic arrest deficient protein MAD2B (MAD2L2) is thought to inhibit the anaphase promoting complex (APC) by binding to CDC20 and/or CDH1 (FZR1), its exact role in cell cycle control still remains to be established. Methodology/Principal Findings: Using a yeast two-hybrid interaction trap we identified the human clathrin light chain A (CLTA) as a novel MAD2B binding protein. A direct interaction was established in mammalian cells via GST pull-down and endogenous co-immunoprecipitation during the G2/M phase of the cell cycle. Through subsequent confocal laser scanning microscopy we found that MAD2B and CLTA co-localize at the mitotic spindle. Clathrin forms a trimeric structure, i.e., the clathrin triskelion, consisting of three heavy chains (CLTC), each with an associated light chain. This clathrin structure has previously been shown to be required for the function of the mitotic spindle through stabilization of kinetochore fibers. Upon siRNA-mediated MAD2B depletion, we found that CLTA was no longer concentrated at the mitotic spindle but, instead, diffusely distributed throughout the cell. In addition, we found a marked increase in the percentage of misaligned chromosomes. Conclusions/Significance: Previously, we identified MAD2B as an interactor of the renal cell carcinoma (RCC)-associated protein PRCC. In addition, we found that fusion of PRCC with the transcription factor TFE3 in t(X;1)(p11;q21)-positive RCCs results in an impairment of this interaction and a concomitant failure to shuttle MAD2B to the nucleus. Our current data show that MAD2B interacts with CLTA during the G2/M phase of the cell cycle and that depletion of MAD2B leads to a marked increase in the percentage of misaligned chromosomes and a redistribution of CLTA during mitosis.

NF-kappa B is dually involved in neurogenesis and brain pathology. Here, we addressed its role in adult axoneogenesis by generating mutations of RelA (p65) and p50 (also known as NFKB1) heterodimers of canonical NF-kappa B. In addition to RelA activation in astrocytes, optic nerve axonotmesis caused a hitherto unrecognized induction of RelA in growth-inhibitory oligodendrocytes. Intraretinally, RelA was induced in severed retinal ganglion cells and was also expressed in bystander Muller glia. Cell-type-specific deletion of transactivating RelA in neurons and/or macroglia stimulated axonal regeneration in a distinct and synergistic pattern. By contrast, deletion of the p50 suppressor subunit promoted spontaneous and post-injury Wallerian degeneration. Growth effects mediated by RelA deletion paralleled a downregulation of growth-inhibitory Cdh1 (officially known as FZR1) and upregulation of the endogenous Cdh1 suppressor EMI1 (officially known as FBXO5). Pro-degenerative loss of p50, however, stabilized retinal Cdh1. In vitro, RelA deletion elicited opposing pro-regenerative shifts in active nuclear and inactive cytoplasmic moieties of Cdh1 and Id2. The involvement of NF-kappa B and cell-cycle regulators such as Cdh1 in regenerative processes of non-replicative neurons suggests novel mechanisms by which molecular reprogramming might be executed to stimulate adult axoneogenesis and treat central nervous system (CNS) axonopathies.