Browsing by Subject "Akt"

Now showing 1 - 6 of 6
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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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    Deletion of the glucocorticoid receptor chaperone FKBP51 prevents glucocorticoid-induced skin atrophy
    (Impact Journals, 2018-10-05) Baida, Gleb; Bhalla, Pankaj; Yemelyanov, Alexander; Stechschulte, Lance A.; Shou, Weinian; Readhead, Ben; Dudley, Joel T.; Sánchez, Edwin R.; Budunova, Irina; Pediatrics, School of Medicine
    FKBP51 (FK506-binding protein 51) is a known co-chaperone and regulator of the glucocorticoid receptor (GR), which usually attenuates its activity. FKBP51 is one of the major GR target genes in skin, but its role in clinical effects of glucocorticoids is not known. Here, we used FKBP51 knockout (KO) mice to determine FKBP51's role in the major adverse effect of topical glucocorticoids, skin atrophy. Unexpectedly, we found that all skin compartments (epidermis, dermis, dermal adipose and CD34+ stem cells) in FKBP51 KO animals were much more resistant to glucocorticoid-induced hypoplasia. Furthermore, despite the absence of inhibitory FKBP51, the basal level of expression and glucocorticoid activation of GR target genes were not increased in FKBP51 KO skin or CRISPR/Cas9-edited FKBP51 KO HaCaT human keratinocytes. FKBP51 is known to negatively regulate Akt and mTOR. We found a significant increase in AktSer473 and mTORSer2448 phosphorylation and downstream pro-growth signaling in FKBP51-deficient keratinocytes in vivo and in vitro. As Akt/mTOR-GR crosstalk is usually negative in skin, our results suggest that Akt/mTOR activation could be responsible for the lack of increased GR function and resistance of FKBP51 KO mice to the steroid-induced skin atrophy.
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    Molecular and Cellular Mechanisms Leading to Similar Phenotypes in Down and Fetal Alcohol Syndromes
    (2013-08-22) Solzak, Jeffrey Peter; Roper, Randall J.; Marrs, James; Kusmierczyk, Andrew; Atkinson, Simon
    Down syndrome (DS) and Fetal Alcohol Syndrome (FAS) are two leading causes of birth defects with phenotypes ranging from cognitive impairment to craniofacial abnormalities. While DS originates from the trisomy of human chromosome 21 and FAS from prenatal alcohol consumption, many of the defining characteristics for these two disorders are stunningly similar. A survey of the literature revealed over 20 similar craniofacial and structural deficits in both human and mouse models of DS and FAS. We hypothesized that the similar phenotypes observed are caused by disruptions in common molecular or cellular pathways during development. To test our hypothesis, we examined morphometric, genetic, and cellular phenotypes during development of our DS and FAS mouse models at embryonic days 9.5-10.5. Our preliminary evidence indicates that during early development, dysregulation of Dyrk1a and Rcan1, cardinal genes affecting craniofacial and neurological precursors of DS, are also dysregulated in embryonic FAS models. Furthermore, Caspase 3 was also found to have similar expression in DS and FAS craniofacial neural crest derived tissues such as the first branchial arch (BA1) and regions of the brain. This may explain a developmental deficit by means of apoptosis. We have also investigated the expression of pAkt, a protein shown to be affected in FAS models, in cells located within the craniofacial precursor of Ts65Dn. Recent research shows that Ttc3, a gene that is triplicated and shown to be overexpressed in the BA1 and neural tube of Ts65Dn, targets pAkt in the nucleus affecting important transcription factors regulating cell cycle and cell survival. While Akt has been shown to play a role in neuronal development, we hypothesize that it also affects similar cellular properties in craniofacial precursors during development. By comparing common genotypes and phenotypes of DS and FAS we may provide common mechanisms to target for potential treatments of both disorders. One of the least understood phenotypes of DS is their deficient immune system. Many individuals with DS have varying serious illnesses ranging from coeliac disease to respiratory infections that are a direct result of this immunodeficiency. Proteasomes are an integral part of a competent and efficient immune system. It has been observed that mice lacking immunoproteasomes present deficiencies in providing MHC class I peptides, proteins essential in identifying infections. A gene, Psmg1 (Dscr2), triplicated in both humans and in Ts65Dn mice, is known to act as a proteasome assembly chaperone for the 20S proteasome. We hypothesized that a dysregulation in this gene promotes a proteasome assembly aberration, impacting the efficiency of the DS immune system. To test this hypothesis we performed western blot analysis on specific precursor and processed β-subunits of the 20S proteasome in thymic tissue of adult Ts65Dn. While the β-subunits tested displayed no significant differences between trisomic and euploid mice we have provided further insight to the origins of immunodeficiency in DS.
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    Preventing tumor progression to the bone by induced tumor-suppressing MSCs: Erratum
    (Ivyspring International, 2022-08-18) Sun, Xun; Li, Kexin; Zha, Rongrong; Liu, Shengzhi; Fan, Yao; Wu, Di; Hase, Misato; Aryal, Uma K.; Lin, Chien-Chi; Yokota, Hiroki; Biomedical Engineering, School of Engineering and Technology
    [This corrects the article DOI: 10.7150/thno.58779.].
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    Pten deletion in Dmp1-expressing cells does not rescue the osteopenic effects of Wnt/β-catenin suppression
    (Wiley, 2020-12) Lim, Kyung-Eun; Hoggatt, April M.; Bullock, Whitney A.; Horan, Daniel J.; Yokota, Hiroki; Pavalko, Frederick M.; Robling, Alexander G.; Anatomy, Cell Biology and Physiology, School of Medicine
    Skeletal homeostasis is sensitive to perturbations in Wnt signaling. Beyond its role in bone, Wnt is a major target for pharmaceutical inhibition in a wide range of diseases, most notably cancers. Numerous clinical trials for Wnt-based candidates are currently underway, and Wnt inhibitors will likely soon be approved for clinical use. Given the bone-suppressive effects accompanying Wnt inhibition, there is a need to expose alternate pathways/molecules that can be targeted to counter the deleterious effects of Wnt inhibition on bone properties. Activation of the Pi3k/Akt pathway via Pten deletion is one possible osteoanabolic pathway to exploit. We investigated whether the osteopenic effects of β-catenin deletion from bone cells could be rescued by Pten deletion in the same cells. Mice carrying floxed alleles for Pten and β-catenin were bred to Dmp1-Cre mice in order to delete Pten alone, β-catenin alone, or both genes, from the late-stage osteoblast/osteocyte population. Mice were assessed for bone mass, density, strength, and formation parameters to evaluate the potential rescue effect of Pten deletion in Wnt-impaired mice. Pten deletion resulted in high bone mass and β-catenin deletion resulted in low bone mass. Compound mutants had bone properties similar to β-catenin mutant mice, or surprisingly in some assays, were further compromised beyond β-catenin mutants. Pten inhibition, or one of its downstream nodes, is unlikely to protect against the bone-wasting effects of Wnt/βcat inhibition. Other avenues for preserving bone mass in the presence of Wnt inhibition should be explored to alleviate the skeletal side effects of Wnt inhibitor-based therapies.
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    Rosmarinic acid interferes with influenza virus A entry and replication by decreasing GSK3β and phosphorylated AKT expression levels
    (Elsevier, 2022) Jheng, Jia-Rong; Hsieh, Chung-Fan; Chang, Yu-Hsiu; Ho, Jin-Yuan; Tang, Wen-Fang; Chen, Zi-Yi; Liu, Chien-Jou; Lin, Ta-Jen; Huang, Li-Yu; Chern, Jyh-Haur; Horng, Jim-Tong; Biochemistry and Molecular Biology, School of Medicine
    Background: The purpose of this study was to examine the in vivo activity of rosmarinic acid (RA) - a phytochemical with antioxidant, anti-inflammatory, and antiviral properties - against influenza virus (IAV). An antibody-based kinase array and different in vitro functional assays were also applied to identify the mechanistic underpinnings by which RA may exert its anti-IAV activity. Methods: We initially examined the potential efficacy of RA using an in vivo mouse model. A time-of-addition assay and an antibody-based kinase array were subsequently applied to investigate mechanism-of-action targets for RA. The hemagglutination inhibition assay, neuraminidase inhibition assay, and cellular entry assay were also performed. Results: RA increased survival and prevented body weight loss in IAV-infected mice. In vitro experiments revealed that RA inhibited different IAV viruses - including oseltamivir-resistant strains. From a mechanistic point of view, RA downregulated the GSK3β and Akt signaling pathways - which are known to facilitate IAV entry and replication into host cells. Conclusions: RA has promising preclinical efficacy against IAV, primarily by interfering with the GSK3β and Akt signaling pathways.