Browsing by Subject "Integrin beta1"
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Item Identification of ITGBL1: A Novel Regulator of Adipogenesis(2016-01-19) Spurgin, Stephen B.; Vishvanath, Lavanya; MacPherson, Karen A.; Hepler, Chelsea; Shao, Mengle; Gupta Rana K.Obesity is a global epidemic that increases the risk for chronic metabolic disease. Pathological expansion of white adipose tissue (WAT) leads to insulin resistance and cardiovascular disease. To date, the mechanisms driving the formation of new adipocytes in obesity remain unclear. We have identified a perivascular (mural) cell population that gives rise to new adipocytes in obese animals. These cells are defined by the expression of Zfp423, a transcription factor that drives the cell differentiation program. Using Zfp423-GFP reporter mice, we have isolated these adipocyte precursors and obtained global gene expression profiles. The most differentially regulated protein was ITGBL1, which was highly expressed in the Zfp423+ mural cells. Given its high expression in these primed early preadipocytes, we investigated the role of ITGBL1 in preadipocyte differentiation in vitro. Here, we show that shRNA or CRISPR-mediated inactivation of ITGBL1 expression increases the propensity of mesenchymal stem cells to undergo adipocyte differentiation. These data suggest that this previously uncharacterized protein serves as an inhibitor or "brake" on the adipocyte differentiation program in preadipocytes. Multiple analyses using available structures of homologous proteins show that Itgbl1 has high structural similarity to DLL1, a known Notch ligand. We show that inactivation of ITGBL1 expression decreases expression of key Notch target genes throughout adipogenesis, thus suggesting a role for ITGBL1 in the activation of Notch signaling (known to inhibit adipogenesis in mesenchymal stem cells in vitro). Ongoing efforts are focused on elucidating ITGBL1's mechanism of action and potential as a novel Notch ligand, as well as its physiological significance in vivo. These studies will lead to a better understanding of how adipose tissue expands in obesity, and how we might promote healthy adipose expansion, preventing insulin resistance and the onset of metabolic syndrome.Item Quantitative Analysis of Integrin Trafficking and Focal Adhesion Turnover to Study Integration of Early Endocytic Trafficking, Signaling and Migration(2019-01-22) Lakoduk, Ashley Marie; Danuser, Gaudenz; Ross, Theodora; Rosen, Michael K.; Schmid, SandraEarly endocytic trafficking is critical for regulating both receptor presence at the plasma membrane and cellular signaling. Clathrin-mediated endocytosis (CME) constitutes a major route of selective receptor internalization, yet little is knowing about how this process is regulated both temporally and spatially. We chose to investigate focal adhesion (FA) and beta-1 integrin turnover as a model system to better understand the spatial, temporal, and cargo-specific regulation of early endocytic trafficking. Importantly, the dynamic turnover of integrins and their associated adhesion complexes through endocytic and recycling pathways has emerged as key mechanism for controlling cancer cell migration and invasion. However, current tools available to study integrin trafficking do not provide adequate spatial information or can induce artifacts. Here, we report the generation and characterization of a neutral and monovalent antibody-based probe to study beta-1 integrin trafficking in cells. Using this tool, we report a novel regulatory mechanism of integrin turnover by a lipid kinase, PIPKI, and discover a mutant p53-driven endosomal signaling nexus that regulates beta-1 integrin recycling and cancer cell invasion. This work demonstrates the importance of the reciprocal crosstalk between early endocytic trafficking and receptor signaling in regulating both normal and tumor cell function.