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  • 1
    Keywords: EXPRESSION ; CELL-PROLIFERATION ; cell cycle ; CELL-CYCLE ; OVEREXPRESSION ; FIBRILLARY ACIDIC PROTEIN ; MICE LACKING VIMENTIN ; INTERMEDIATE-FILAMENT NETWORKS ; UBIQUITIN-PROTEASOME PATHWAY ; LACERATED CORNEAS ; MUSCLE ALPHA-ACTIN ; MYOFIBROBLAST DIFFERENTIATION ; RETINAL-DETACHMENT ; WITHAFERIN-A
    Abstract: The type III intermediate filaments (IFs) are essential cytoskeletal elements of mechanosignal transduction and serve critical roles in tissue repair. Mice genetically deficient for the IF protein vimentin (Vim(-/-)) have impaired wound healing from deficits in myofibroblast development. We report a surprising finding made in Vim(-/-) mice that corneas are protected from fibrosis and instead promote regenerative healing after traumatic alkali injury. This reparative phenotype in Vim(-/-) corneas is strikingly recapitulated by the pharmacological agent withaferin A (WFA), a small molecule that binds to vimentin and downregulates its injury-induced expression. Attenuation of corneal fibrosis by WFA is mediated by downregulation of ubiquitin conjugating E3 ligase Skp2 and upregulation of cyclin-dependent kinase inhibitors (CKIs) p27(Kip1) and p21(Cip1). In cell culture models, WFA exerts G2/M cell cycle arrest in a p27(Kip1) and Skp2-dependent manner. Finally, by developing a highly sensitive imaging method to measure corneal opacity, we identify a novel role for desmin overexpression in corneal haze. We demonstrate that desmin downregulation by WFA via targeting the conserved WFA-ligand binding site shared among type III IFs promotes further improvement of corneal transparency without affecting CKI levels in Vim(-/-) mice. This dissociates a direct role for desmin in corneal cell proliferation. Taken together, our findings illuminate a previously unappreciated pathogenic role for type III IF overexpression in corneal fibrotic conditions and also validate WFA as a powerful drug lead towards anti-fibrosis therapeutic development.
    Type of Publication: Journal article published
    PubMed ID: 22117063
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  • 2
    Keywords: CANCER ; CELLS ; RISK ; TUMORS ; FAMILY ; BIOLOGY ; SUSCEPTIBILITY ; BREAST ; BREAST-CANCER ; STEM-CELLS ; MULTIPLE-MYELOMA ; MAMMARY-GLAND ; MUTATION CARRIERS ; ADHERENS JUNCTIONS ; EPITHELIUM ; MISSENSE MUTATIONS ; genetic variation ; MITOTIC SPINDLE ; BRCA1-DEPENDENT UBIQUITINATION ; CENTROSOMAL MICROTUBULE NUCLEATION ; PROGENITOR-CELL FATE
    Abstract: Differentiated mammary epithelium shows apicobasal polarity, and loss of tissue organization is an early hallmark of breast carcinogenesis. In BRCA1 mutation carriers, accumulation of stem and progenitor cells in normal breast tissue and increased risk of developing tumors of basal-like type suggest that BRCA1 regulates stem/progenitor cell proliferation and differentiation. However, the function of BRCA1 in this process and its link to carcinogenesis remain unknown. Here we depict a molecular mechanism involving BRCA1 and RHAMM that regulates apicobasal polarity and, when perturbed, may increase risk of breast cancer. Starting from complementary genetic analyses across families and populations, we identified common genetic variation at the low-penetrance susceptibility HMMR locus (encoding for RHAMM) that modifies breast cancer risk among BRCA1, but probably not BRCA2, mutation carriers: n = 7,584, weighted hazard ratio ((w)HR) = 1.09 (95% CI 1.02-1.16), p(trend) = 0.017; and n = 3,965, (w)HR = 1.04 (95% CI 0.94-1.16), p(trend) = 0.43; respectively. Subsequently, studies of MCF10A apicobasal polarization revealed a central role for BRCA1 and RHAMM, together with AURKA and TPX2, in essential reorganization of microtubules. Mechanistically, reorganization is facilitated by BRCA1 and impaired by AURKA, which is regulated by negative feedback involving RHAMM and TPX2. Taken together, our data provide fundamental insight into apicobasal polarization through BRCA1 function, which may explain the expanded cell subsets and characteristic tumor type accompanying BRCA1 mutation, while also linking this process to sporadic breast cancer through perturbation of HMMR/RHAMM.
    Type of Publication: Journal article published
    PubMed ID: 22110403
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