In order to discover previously unidentified cancer-associated genes, we analyzed genome-wide differences in gene expression between tumor biopsies and normal tissues. Among those differentially regulated genes, we identified Sharpin (Shank-associated RH domain-interacting protein) as a commonly up-regulated gene in multiple human cancer types. Although rat Sharpin is reported to interact with Shank1, a multidomain scaffold protein localized in postsynaptic densities, its exact roles are unknown. Whereas human Sharpin homologue was primarily localized in the cytosol of cultured cells, they were detected in both cytosol and nucleus of the cells from ovarian and liver cancer tissues using immunohistochemical staining. In addition, Chinese ovary hamster cells over-expressing Sharpin exhibited enhanced cancer-specific phenotypes in multiple in vitro tumor assays. Taken together, the results suggest that Sharpin is not an inert scaffold protein, but may play tumor-associated roles during cancer biogenesis.

Lipid droplet (LD) accumulation, a key feature of foam cells, constitutes an attractive target for therapeutic intervention in atherosclerosis. However, despite advances in cellular imaging techniques, current noninvasive and quantitative methods have limited application in living foam cells. Here, using optical diffraction tomography (ODT), we performed quantitative morphological and biophysical analysis of living foam cells in a label-free manner. We identified LDs in foam cells by verifying the specific refractive index using correlative imaging comprising ODT integrated with three-dimensional fluorescence imaging. Through time-lapse monitoring of threedimensional dynamics of label-free living foam cells, we precisely and quantitatively evaluated the therapeutic effects of a nanodrug (mannose−polyethylene glycol−glycol chitosan−fluorescein isothiocyanate−lobeglitazone; MMR-Lobe) designed to affect the targeted delivery of lobeglitazone to foam cells based on high mannose receptor specificity. Furthermore, by exploiting machine-learning-based image analysis, we further demonstrated therapeutic evaluation at the single-cell level. These findings suggest that refractive index measurement is a promising tool to explore new drugs against LD-related metabolic diseases.

CENP-W was originally identified as a putative oncogene, cancer-upregulated gene 2 (CUG2) that was commonly up-regulated in many cancer tissues. Recently, CENP-W has also been identified as a new centromeric component that interacts with CENP-T. As a complex with CENP-T, CENP-W plays crucial roles in assembly of the functional kinetochore complex. In this study, the subnuclear localization of CENP-W was extensively analyzed using various approaches. We found that ectopically expressed CENP-W primarily accumulated in the nucleolus and remained substantially associated with the nucleolus in stable cells. The following fractionation study also showed that CENP-W is associated with RNA as well as DNA. Moreover, a considerable amount of CENP-W was found in the nuclear mesh-like structure, nuclear matrix, possibly indicating that CENP-W participates in diverse subnuclear activities. Finally, biochemical affinity binding analysis revealed that CENP-W specifically interacts with the nucleolar phosphoprotein, nucleophosmin (B23). Depletion of cellular B23 by siRNA treatment induced a dramatic decrease of CENP-W stability and severe mislocalization during prophase. Our data proposed that B23 may function in the assembly of the kinetochore complex by interacting with CENP-W during interphase.

Neuronal growth regulator 1 (NEGR1) is a GPI-anchored membrane protein that is involved in neural cell adhesion and communication. Multiple genome wide association studies have found that NEGR1 is a generic risk factor for multiple human diseases, including obesity, autism, and depression. Recently, we reported that Negr1 −/− mice showed a highly increased fat mass and affective behavior. In the present study, we identified Na/K-ATPase, beta1-subunit (ATP1B1) as an NEGR1 binding partner by yeast two-hybrid screening. NEGR1 and ATP1B1 were found to form a relatively stable complex in cells, at least partially co-localizing in membrane lipid rafts. We found that NEGR1 binds with ATP1B1 at its C-terminus, away from the binding site for the alpha subunit, and may contribute to intercellular interactions. Collectively, we report ATP1B1 as a novel NEGR1-interacting protein, which may help deciphering molecular networks underlying NEGR1-associated human diseases. [BMB Reports 2021; 54(3): 164-169] BMB Rep. 2021; 54(3): 164-169 www.bmbreports.org ATP1B1 is a new binding partner of NEGR1 Yeongmi Cheon, et al.