Browsing by Subject "Nucleus"

Now showing 1 - 3 of 3
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    Cell Mechanosensitivity to Extremely Low Magnitude Signals is Enabled by a LINCed Nucleus
    (Wiley, 2015-06) Uzer, Gunes; Thompson, William R.; Sen, Buer; Xie, Zhihui; Yen, Sherwin S.; Miller, Sean; Bas, Guniz; Styner, Maya; Rubin, Clinton T.; Judex, Stefan; Burridge, Keith; Rubin, Janet; Physical Therapy, School of Health and Rehabilitation Sciences
    A cell's ability to recognize and adapt to the physical environment is central to its survival and function, but how mechanical cues are perceived and transduced into intracellular signals remains unclear. In mesenchymal stem cells (MSCs), high-magnitude substrate strain (HMS, ≥2%) effectively suppresses adipogenesis via induction of focal adhesion (FA) kinase (FAK)/mTORC2/Akt signaling generated at FAs. Physiologic systems also rely on a persistent barrage of low-level signals to regulate behavior. Exposing MSC to extremely low-magnitude mechanical signals (LMS) suppresses adipocyte formation despite the virtual absence of substrate strain (<0.001%), suggesting that LMS-induced dynamic accelerations can generate force within the cell. Here, we show that MSC response to LMS is enabled through mechanical coupling between the cytoskeleton and the nucleus, in turn activating FAK and Akt signaling followed by FAK-dependent induction of RhoA. While LMS and HMS synergistically regulated FAK activity at the FAs, LMS-induced actin remodeling was concentrated at the perinuclear domain. Preventing nuclear-actin cytoskeleton mechanocoupling by disrupting linker of nucleoskeleton and cytoskeleton (LINC) complexes inhibited these LMS-induced signals as well as prevented LMS repression of adipogenic differentiation, highlighting that LINC connections are critical for sensing LMS. In contrast, FAK activation by HMS was unaffected by LINC decoupling, consistent with signal initiation at the FA mechanosome. These results indicate that the MSC responds to its dynamic physical environment not only with "outside-in" signaling initiated by substrate strain, but vibratory signals enacted through the LINC complex enable matrix independent "inside-inside" signaling.
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    Passage dependent changes in nuclear and cytoskeleton structures of endothelial cells under laminar shear stress or cyclic stretch
    (Medip Academy, 2021) Jiang, Yizhi; Witt, Nathaniel; Ji, Julie Y.; Biomedical Engineering, Purdue School of Engineering and Technology
    Background: The ability of vascular endothelium to sense and respond to the mechanical stimuli generated by blood flow is pivotal in maintaining arterial homeostasis. A steady laminar flow tends to provide athero-protective effect via regulating endothelial functions, vascular tone, and further remodeling process. As arterial aging appeared to be an independent risk factor of cardiovascular diseases, it is critical to understand the effects of cell senescence on endothelial dysfunction under dynamic mechanical stimuli. Methods: In this study, we investigated the morphological responses of aortic endothelial cells toward laminar flow or cyclic stretch. Automated image recognition methods were applied to analyze image data to avoid bias. Differential patterns of morphological adaptations toward distinct mechanical stimuli were observed, and the shear-induced changes were found to be more associated with cell passages than that of cyclic strain. Results: Our results demonstrated that the cytoskeleton and nuclear structural adaptations in endothelial cells toward laminar flow were altered over prolonged culture, suggesting that the failure of senescent endothelial cells to adapt to the applied shear stress morphologically could be one of the contributors to endothelial dysfunctions during vascular aging. Conclusions: Results indicated that cells were able to adjust their cytoskeleton and nuclear alignment and nuclear shapes in response to the applied mechanical stimuli, and that the shear-induced changes were more dependent on PD levels, where cells with higher PDL were more responsive to external forces.
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    Proteomic analysis of murine kidney proximal tubule sub-segment derived cell lines reveals preferences in mitochondrial pathway activity
    (Elsevier, 2023) Ferreira, Ricardo Melo; de Almeida, Rita; Culp, Clayton; Witzmann, Frank; Wang, Mu; Kher, Rajesh; Nagami, Glenn T.; Mohallem, Rodrigo; Andolino, Chaylen Jade; Aryal, Uma K.; Eadon, Michael T.; Bacallao, Robert L.; Medicine, School of Medicine
    The proximal tubule (PT) is a nephron segment that is responsible for the majority of solute and water reabsorption in the kidney. Each of its sub-segments have specialized functions; however, little is known about the genes and proteins that determine the oxidative phosphorylation capacity of the PT sub-segments. This information is critical to understanding kidney function and will provide a comprehensive landscape of renal cell adaptations to injury, physiologic stressors, and development. This study analyzed three immortalized murine renal cell lines (PT S1, S2, and S3 segments) for protein content and compared them to a murine fibroblast cell line. All three proximal tubule cell lines generate ATP predominantly by oxidative phosphorylation while the fibroblast cell line is glycolytic. The proteomic data demonstrates that the most significant difference in proteomic signatures between the cell lines are proteins known to be localized in the nucleus followed by mitochondrial proteins. Mitochondrial metabolic substrate utilization assays were performed using the proximal tubule cell lines to determine substrate utilization kinetics thereby providing a physiologic context to the proteomic dataset. This data will allow researchers to study differences in nephron-specific cell lines, between epithelial and fibroblast cells, and between actively respiring cells and glycolytic cells. SIGNIFICANCE: Proteomic analysis of proteins expressed in immortalized murine renal proximal tubule cells was compared to a murine fibroblast cell line proteome. The proximal tubule segment specific cell lines: S1, S2 and S3 are all grown under conditions whereby the cells generate ATP by oxidative phosphorylation while the fibroblast cell line utilizes anaerobic glycolysis for ATP generation. The proteomic studies allow for the following queries: 1) comparisons between the proximal tubule segment specific cell lines, 2) comparisons between polarized epithelia and fibroblasts, 3) comparison between cells employing oxidative phosphorylation versus anaerobic glycolysis and 4) comparisons between cells grown on clear versus opaque membrane supports. The data finds major differences in nuclear protein expression and mitochondrial proteins. This proteomic data set will be an important baseline dataset for investigators who need immortalized renal proximal tubule epithelial cells for their research.