Browsing by Author "Yao, Tso-Pang"
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Item Open Access Branched-Chain Amino Acid Accumulation Fuels the Senescence-Associated Secretory Phenotype.(Advanced science (Weinheim, Baden-Wurttemberg, Germany), 2023-11) Liang, Yaosi; Pan, Christopher; Yin, Tao; Wang, Lu; Gao, Xia; Wang, Ergang; Quang, Holly; Huang, De; Tan, Lianmei; Xiang, Kun; Wang, Yu; Alexander, Peter B; Li, Qi-Jing; Yao, Tso-Pang; Zhang, Zhao; Wang, Xiao-FanThe essential branched-chain amino acids (BCAAs) leucine, isoleucine, and valine play critical roles in protein synthesis and energy metabolism. Despite their widespread use as nutritional supplements, BCAAs' full effects on mammalian physiology remain uncertain due to the complexities of BCAA metabolic regulation. Here a novel mechanism linking intrinsic alterations in BCAA metabolism is identified to cellular senescence and the senescence-associated secretory phenotype (SASP), both of which contribute to organismal aging and inflammation-related diseases. Altered BCAA metabolism driving the SASP is mediated by robust activation of the BCAA transporters Solute Carrier Family 6 Members 14 and 15 as well as downregulation of the catabolic enzyme BCAA transaminase 1 during onset of cellular senescence, leading to highly elevated intracellular BCAA levels in senescent cells. This, in turn, activates the mammalian target of rapamycin complex 1 (mTORC1) to establish the full SASP program. Transgenic Drosophila models further indicate that orthologous BCAA regulators are involved in the induction of cellular senescence and age-related phenotypes in flies, suggesting evolutionary conservation of this metabolic pathway during aging. Finally, experimentally blocking BCAA accumulation attenuates the inflammatory response in a mouse senescence model, highlighting the therapeutic potential of modulating BCAA metabolism for the treatment of age-related and inflammatory diseases.Item Open Access Cathelicidin-related antimicrobial peptide mediates skeletal muscle degeneration caused by injury and Duchenne muscular dystrophy in mice.(Journal of cachexia, sarcopenia and muscle, 2022-12) Choi, Moon-Chang; Jo, Jiwon; Lee, Myeongjin; Park, Jonggwan; Yao, Tso-Pang; Park, YoonkyungBackground
Cathelicidin, an antimicrobial peptide, plays a key role in regulating bacterial killing and innate immunity; however, its role in skeletal muscle function is unknown. We investigated the potential role of cathelicidin in skeletal muscle pathology resulting from acute injury and Duchenne muscular dystrophy (DMD) in mice.Methods
Expression changes and muscular localization of mouse cathelicidin-related antimicrobial peptide (Cramp) were examined in the skeletal muscle of normal mice treated with chemicals (cardiotoxin and BaCl2 ) or in dystrophic muscle of DMD mouse models (mdx, mdx/Utrn+/- and mdx/Utrn-/- ). Cramp penetration into myofibres and effects on muscle damage were studied by treating synthetic peptides to mouse skeletal muscles or C2C12 myotubes. Cramp knockout (KO) mice and mdx/Utrn/Cramp KO lines were used to determine whether Cramp mediates muscle degeneration. Muscle pathophysiology was assessed by histological methods, serum analysis, grip strength and lifespan. Molecular factors targeted by Cramp were identified by the pull-down assay and proteomic analysis.Results
In response to acute muscle injury, Cramp was activated in muscle-infiltrating neutrophils and internalized into myofibres. Cramp treatments of mouse skeletal muscles or C2C12 myotubes resulted in muscle degeneration and myotube damage, respectively. Genetic ablation of Cramp reduced neutrophil infiltration and ameliorated muscle pathology, such as fibre size (P < 0.001; n = 6) and fibrofatty infiltration (P < 0.05). Genetic reduction of Cramp in mdx/Utrn+/- mice not only attenuated muscle damage (35%, P < 0.05; n = 9-10), myonecrosis (53%, P < 0.05), inflammation (37-65%, P < 0.01) and fibrosis (14%, P < 0.05) but also restored muscle fibre size (14%, P < 0.05) and muscle force (18%, P < 0.05). Reducing Cramp levels led to a 63% (male, P < 0.05; n = 10-14) and a 124% (female, P < 0.001; n = 20) increase in the lifespan of mdx/Utrn-/- mice. Proteomic and mechanistic studies revealed that Cramp cross-talks with Ca2+ signalling in skeletal muscle through sarcoplasmic/endoplasmic reticulum Ca2+ -ATPase1 (SERCA1). Cramp binds and inactivates SERCA1, leading to the activation of Ca2+ -dependent calpain proteases that exacerbate DMD progression.Conclusions
These findings identify Cramp as an immune cell-derived regulator of skeletal muscle degeneration and provide a potential therapeutic target for DMD.Item Open Access CoA synthase regulates mitotic fidelity via CBP-mediated acetylation.(Nature communications, 2018-03-12) Lin, Chao-Chieh; Kitagawa, Mayumi; Tang, Xiaohu; Hou, Ming-Hsin; Wu, Jianli; Qu, Dan Chen; Srinivas, Vinayaka; Liu, Xiaojing; Thompson, J Will; Mathey-Prevot, Bernard; Yao, Tso-Pang; Lee, Sang Hyun; Chi, Jen-TsanThe temporal activation of kinases and timely ubiquitin-mediated degradation is central to faithful mitosis. Here we present evidence that acetylation controlled by Coenzyme A synthase (COASY) and acetyltransferase CBP constitutes a novel mechanism that ensures faithful mitosis. We found that COASY knockdown triggers prolonged mitosis and multinucleation. Acetylome analysis reveals that COASY inactivation leads to hyper-acetylation of proteins associated with mitosis, including CBP and an Aurora A kinase activator, TPX2. During early mitosis, a transient CBP-mediated TPX2 acetylation is associated with TPX2 accumulation and Aurora A activation. The recruitment of COASY inhibits CBP-mediated TPX2 acetylation, promoting TPX2 degradation for mitotic exit. Consistently, we detected a stage-specific COASY-CBP-TPX2 association during mitosis. Remarkably, pharmacological and genetic inactivation of CBP effectively rescued the mitotic defects caused by COASY knockdown. Together, our findings uncover a novel mitotic regulation wherein COASY and CBP coordinate an acetylation network to enforce productive mitosis.Item Open Access Distinct functions of POT1 at telomeres.(2008) Kendellen, Megan FullerTelomeres are nucleoprotein complexes that constitute the ends of eukaryotic chromosomes. Telomeres differentiate the end of the chromosome from sites of DNA damage and control cellular replicative potential. The loss of function of telomeres results in several biological consequences. First, dysfunctional telomeres elicit DNA damage responses and repair activities, which frequently induce cytogenetic abnormalities and genomic instability that are characteristic of human cancer. Second, cellular immortalization resulting from inappropriate elongation of telomeres is a critical component of tumorigenesis. Alternatively, as telomere shortening limits replicative potential, abnormally short telomeres can result in premature cellular senescence that is associated with human pathology ranging from anemia to atherosclerosis. Telomeric DNA is composed of tandem repeats of G‐rich double‐stranded (ds)DNA that terminates in a G‐rich 3’ single‐stranded (ss)DNA overhang. Telomeres are thought to assume a lariat structure termed the t‐loop, which is decorated by an assortment of telomere‐associated proteins. The most unique and least well characterized of these proteins is POT1. POT1 binds telomeric ssDNA via a pair of Nterminal OB‐folds. Through its C‐terminal protein‐interaction domain, POT1 directly binds the telomeric dsDNA‐binding protein TRF2 and participates in heterodimeric complex with the protein TPP1. Inhibition of POT1 induces a robust DNA damage response at telomeres and deregulation of telomere length homeostasis, indicating that POT1 is important in maintaining telomere stability and in regulating telomere length. The goal of my thesis work was to determine which of the three major functions of POT1– telomeric ssDNA‐, TPP1‐, or TRF2‐binding – were required to properly localize POT1 to telomeres and to prevent the telomere instability and length deregulation that occur in the absence of POT1. Using separation‐of‐function mutants of POT1 deficient in at least one of these activities, I found that POT1 depends on its heterodimeric partner TPP1 in cis with telomeric ssDNA‐binding to preserve telomere stability, while POT1 depends on its protein interaction with TRF2 to localize to telomeres and its TRF2‐ and telomeric ssDNA‐binding activities in cis to regulate telomere length.Item Open Access Quality control autophagy: a joint effort of ubiquitin, protein deacetylase and actin cytoskeleton.(Autophagy, 2010-05) Lee, Joo-Yong; Yao, Tso-PangAutophagy has been predominantly studied as a nonselective self-digestion process that recycles macromolecules and produces energy in response to starvation. However, autophagy independent of nutrient status has long been known to exist. Recent evidence suggests that this form of autophagy enforces intracellular quality control by selectively disposing of aberrant protein aggregates and damaged organelles--common denominators in various forms of neurodegenerative diseases. By definition, this form of autophagy, termed quality-control (QC) autophagy, must be different from nutrient-regulated autophagy in substrate selectivity, regulation and function. We have recently identified the ubiquitin-binding deacetylase, HDAC6, as a key component that establishes QC. HDAC6 is not required for autophagy activation per se; rather, it is recruited to ubiquitinated autophagic substrates where it stimulates autophagosome-lysosome fusion by promoting F-actin remodeling in a cortactin-dependent manner. Remarkably, HDAC6 and cortactin are dispensable for starvation-induced autophagy. These findings reveal that autophagosomes associated with QC are molecularly and biochemically distinct from those associated with starvation autophagy, thereby providing a new molecular framework to understand the emerging complexity of autophagy and therapeutic potential of this unique machinery.Item Open Access Roles of Cytoplasmic Deacetylase Hdac6 in Oncogenic Tumorigenesis(2008-04-21) Lee, YishanReversible acetylation has emerged as an important post-translational modification that rivals phosphorylation in regulating chromatin structure and gene expression. Acetylation of histone is associated with transcriptional activation while deacetylation is linked to transcriptional repression. Moreover, histone deacetylase inhibitors induce growth arrest, differentiation and apoptosis of cancer cells and therefore appear to be promising anti-tumor agents. While transcriptional deregulation is thought to be the main mechanism underlying their therapeutic effects, the exact mechanisms and targets by which HDAC inhibitors, which are mostly non-specific, achieve their anti-tumor effects remain poorly understood. In other words, it is not known which and how each HDAC members are involved in supporting tumor growth.
In this thesis, I have showed that HDAC6, a cytoplasmic localized and cytoskeleton-associated deacetylase, is required for efficient oncogenic transformation and tumor formation. I have found that HDAC6 expression is induced upon oncogenic Ras-induced transformation in both human somatic cells and murine fibroblasts. Conversely, murine fibroblasts deficient in HDAC6 are more resistant to both oncogenic Ras and ErbB2-dependent transformation, indicating a critical role for HDAC6 in oncogene-induced transformation. Supporting this hypothesis, inactivation of HDAC6 in several human cancer cell lines effectively impairs anchorage-independent growth in vitro and their ability to form tumors in immunocompromised mice. I have demonstrated that the impairment of anchorage independent growth in HDAC6 deficient cells is associated with increased anoikis and mechanistically a defect in activation of the AKT and ERK kinase cascades. Additionally, HDAC6 null mice are more resistant to two-stage chemical carcinogen-induced skin tumors. Finally, I have demonstrated that the tumor-promoting effect of HDAC6 is probably mediated through the molecular chaperon Hsp90. While Hsp90 is known to be deacetylated by HDAC6 and has been implicated in stabilizing Raf-1 and ErbB2, I have found that suppression of HDAC6 impairs the stability of Raf-1 and the association between Hsp90 and ErbB2.
In conclusion, my work provides the first experimental evidence that of all the HDAC members, the cytoplasmic deacetylase HDAC6 is required for efficient oncogenic transformation, indicating that reversible acetylation plays a critical role in regulating cellular functions of non-histone non-nuclear cytoplasmic proteins that contributes to malignant transformation. Furthermore, this work identifies HDAC6 as an important component underlying the anti-tumor effects of HDAC inhibitors.
Item Open Access VCP/p97 is essential for maturation of ubiquitin-containing autophagosomes and this function is impaired by mutations that cause IBMPFD.(Autophagy, 2010-02) Tresse, Emilie; Salomons, Florian A; Vesa, Jouni; Bott, Laura C; Kimonis, Virginia; Yao, Tso-Pang; Dantuma, Nico P; Taylor, J PaulVCP (VCP/p97) is a ubiquitously expressed member of the AAA(+)-ATPase family of chaperone-like proteins that regulates numerous cellular processes including chromatin decondensation, homotypic membrane fusion and ubiquitin-dependent protein degradation by the proteasome. Mutations in VCP cause a multisystem degenerative disease consisting of inclusion body myopathy, Paget disease of bone, and frontotemporal dementia (IBMPFD). Here we show that VCP is essential for autophagosome maturation. We generated cells stably expressing dual-tagged LC3 (mCherry-EGFP-LC3) which permit monitoring of autophagosome maturation. We determined that VCP deficiency by RNAi-mediated knockdown or overexpression of dominant-negative VCP results in significant accumulation of immature autophagic vesicles, some of which are abnormally large, acidified and exhibit cathepsin B activity. Furthermore, expression of disease-associated VCP mutants (R155H and A232E) also causes this autophagy defect. VCP was found to be essential to autophagosome maturation under basal conditions and in cells challenged by proteasome inhibition, but not in cells challenged by starvation, suggesting that VCP might be selectively required for autophagic degradation of ubiquitinated substrates. Indeed, a high percentage of the accumulated autophagic vesicles contain ubiquitin-positive contents, a feature that is not observed in autophagic vesicles that accumulate following starvation or treatment with Bafilomycin A. Finally, we show accumulation of numerous, large LAMP-1 and LAMP-2-positive vacuoles and accumulation of LC3-II in myoblasts derived from patients with IBMPFD. We conclude that VCP is essential for maturation of ubiquitin-containing autophagosomes and that defect in this function may contribute to IBMPFD pathogenesis.