MyosinⅥ is a Mediator of the p53-dependent Cell Survival Pathway Yoshihito Komoriya Benesh Joseph Molecular And Cellular B...
Introduction <ul><li>MyosinⅥ is a unconventional motor protein and is responsible for actin-based motility, and MyosinⅥ </...
Research  Aim  <ul><li>To find how myosinⅥ is regulated and its function in the DNA  </li></ul><ul><li>damage response.  <...
About  p 53 <ul><li>p53 , also known as  tumor protein 53  (TP53), is a transcription  </li></ul><ul><li>factor that regul...
Apoptosis <ul><li>Apoptosis  is a process of deliberate life relinquishment by a cell in a multicellular organism.   It is...
<ul><li>Myosin VI is a novel target gene of p53. (A) Myosin VI is induced by p53 in a time-dependent manner. (B) Induction...
FIG. 2  (A) The induction of myosin VI by DNA damage is dependent on p53. RKO and RKO-p53-KD were untreated (–) or treated...
<ul><li>FIG. 3. Myosin VI is a direct target of the p53 transcription factor.  </li></ul><ul><li>(A) Schematic presentatio...
<ul><li>(C) Schematic presentation of 11 additional myosin VI promoter/reporter constructs with deletion in the GC-rich re...
F <ul><li>(F ) Schematic representation of the myosin VI  promoters with the locations of the transcription start site, p5...
summary <ul><li>・ MyosinⅥ is induced in a p53 dependent manner during DNA damage  </li></ul><ul><li>・ p53 binds directly t...
Cell lines Used to Study the Intracellular Localization of Myosin VI H24-208   - expresses Flag-tagged  wild-type p53  by ...
In presence of p53, Myosin VI Is  localized to Golgy complex,  Perinuclear membrane  and Nucleus A.  RKO cell line,  B.  R...
Myosin VI localization in  trans -Golgi  is confirmed by the co-localization  with the trans-Golgy marker TGN  p230.  H24-...
Nuclear Localization of Myosin VI is increased by p53 Myosin VI is required for efficient stabilization of p53 by DNA dama...
D M Myosin VI knock down impairs myosin VI mediated maintenance of Golgi  complex  integrity  Intracellular localization o...
Myosin VI knock down increased Doxorubicin induced apoptosis from  43 to 55% in RKO cells. Caspases  are proteases that me...
ATM is a Kinase activated by DNA damage. It  phosphorylate and activate p53. phosphorylated p53 is stable against the mdm2...
Conclusions: p53 binds directly to the promoter of the myosin VI gene and transcriptionally regulates myosin VI gene expre...
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1. Myosinⅵ Is A Mediator Of The P53 Dependent Cell

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  • 1. Myosinⅵ Is A Mediator Of The P53 Dependent Cell

    1. 1. MyosinⅥ is a Mediator of the p53-dependent Cell Survival Pathway Yoshihito Komoriya Benesh Joseph Molecular And Cellular Biology March 2006, p2175-2186. Impact Factor 7.093
    2. 2. Introduction <ul><li>MyosinⅥ is a unconventional motor protein and is responsible for actin-based motility, and MyosinⅥ </li></ul><ul><li>play a key role in the protein trafficking and homeostasis </li></ul><ul><li>of the Golgi complex and so on. </li></ul>Function of MyosinⅥ ・ Moving endocytic vesicles in epithelial cell ・ protein secretion and maintenance in Golgi complex Cell migration in membrane ruffles ・ Maintaining of hearing capability in ear stereocilia But very little known about how myosinⅥ is regulated and function in the DNA damage response.
    3. 3. Research Aim <ul><li>To find how myosinⅥ is regulated and its function in the DNA </li></ul><ul><li>damage response. </li></ul>1.p53 regulates myosin VI in two major pathways: transactivation of myosin VI gene expression and intracellular localization of myosin VI protein 2.During DNA damage response, Myosin VI is regulated in a p53-dependent manner. Findings
    4. 4. About p 53 <ul><li>p53 , also known as tumor protein 53 (TP53), is a transcription </li></ul><ul><li>factor that regulates the cell cycle and hence functions as a </li></ul><ul><li>tumor suppressor </li></ul>Functions of p53 ・ activation of DNA repair proteins when DNA has sustained damage ・ holding the cell cycle at the G1/S regulation point on DNA damage recognition ・ Initiation of apoptosis
    5. 5. Apoptosis <ul><li>Apoptosis is a process of deliberate life relinquishment by a cell in a multicellular organism. It is one of the main types of programmed cell death. </li></ul><ul><li>Apoptosis can occur when a cell is damaged beyond repair, infected with a virus, or undergoing stress conditions such as starvation. </li></ul><ul><li>DNA damage from ionizing radiation or toxic chemicals can also induce apoptosis via the actions of the tumour-suppressing gene p53 . </li></ul>
    6. 6. <ul><li>Myosin VI is a novel target gene of p53. (A) Myosin VI is induced by p53 in a time-dependent manner. (B) Induction of myosin VI by wild-type and various mutated forms of p53. (C) Myosin VI is induced by DNA damage in a p53-dependent manner. RKO and LS174T were either untreated (–) or treated (+) with 300 nM camptothecin for 24 h. </li></ul><ul><li>camptothecin      aninhibitor of topoisomerase Ⅰwhich can </li></ul><ul><li>induce double-strand breaks. </li></ul>
    7. 7. FIG. 2 (A) The induction of myosin VI by DNA damage is dependent on p53. RKO and RKO-p53-KD were untreated (–) or treated with dimethyl sulfoxide (DMSO), 0.2 µg/ml of doxorubicin (DOX), or 200 nM camptothecin (CPT). (B) The level of myosin VI protein is increased by DNA damage in a time-dependent manner. RKO cells were untreated (–) or treated with 0.2 µg/ml of DMSO, 0.2 µg/ml of doxorubicin, or 100 nM camptothecin for 12, 24, and 48 h. (C) The level of myosin VI is increased by DNA damage in a p53-dependent manner. RKO, LS174T, and HeLa cells were treated with 0, 0.1, 0.3, or 0.5 µg/ml of doxorubicin. Whole-cell extracts were analyzed by Western blotting with antibodies as indicated. Actin was analyzed as a loading control. Doxorubcin ・・・ drug which stabilizes the topoisomerase II complex after it has broken the DNA chain for replication, preventing the DNA double helix from being resealed and thereby stopping the process of replication.
    8. 8. <ul><li>FIG. 3. Myosin VI is a direct target of the p53 transcription factor. </li></ul><ul><li>(A) Schematic presentation of the human myosin VI gene locus and luciferase (Luc) reporter constructs. Box A represents a potential p53-binding site from nt –347 to –325, whereas box B is a GC-rich region from nt –171 to –72. </li></ul><ul><li>(B) The GC-rich region in the myosin VI promoter is responsive to wild-type (wt) p53, but not mutant (mut) p53. con means control. </li></ul>
    9. 9. <ul><li>(C) Schematic presentation of 11 additional myosin VI promoter/reporter constructs with deletion in the GC-rich region. </li></ul><ul><li>(D and E) The GC-rich region is required for p53 transactivation of the myosin VI promoter </li></ul>
    10. 10. F <ul><li>(F ) Schematic representation of the myosin VI promoters with the locations of the transcription start site, p53-responsive elements, and primers used for ChIP assays. </li></ul><ul><li>(G) p53 binds directly to the myosin VI promoter. </li></ul>G F
    11. 11. summary <ul><li>・ MyosinⅥ is induced in a p53 dependent manner during DNA damage </li></ul><ul><li>・ p53 binds directly to promoter of MyosinⅥ gene and transpcritionally regulates MyosinⅥ   expression. </li></ul>
    12. 12. Cell lines Used to Study the Intracellular Localization of Myosin VI H24-208 - expresses Flag-tagged wild-type p53 by the ecdysone inducible system and HA-tagged mutant p53 (R273H) by the tetracycline-inducible system. H24-112 - expresses Hemeagglutinin-tagged wild-type p53 by the ecdysone-inducible system and HA-tagged wild-type p73 by the tetracycline-inducible system (A) Myosin VI is induced by wild-type (wt) p53, but not mutant (mut) p53(R273H). H24-208 cells were uninduced (control), induced to express wild-type p53, induced to express mutant p53(R273H), or induced to express both for 48 h. The expression level of wild-type p53, mutant p53, myosin VI, p21, and GBF was quantified by Western blot analysis. Actin was analyzed as a loading control. (B) Myosin VI is induced by wild-type p53, but not wild-type p73. H24-112 cells were uninduced (control), induced to express wild-type p73, induced to express wild-type p53, or induced to express both for 48 h. The expression level of p73, p53, myosin VI, p21, and p115 was quantified by Western blot analysis.
    13. 13. In presence of p53, Myosin VI Is localized to Golgy complex, Perinuclear membrane and Nucleus A. RKO cell line, B. RKO p53-KD cell line The intracellular localization of myosin VI is altered by wild-type p53, which is inhibited by mutant p53(R273H). Immunofluorescence staining - p53 was stained green, whereas myosin VI was stained red. Nuclei were stained blue. con, control. (A and B) Intracellular localization of myosin VI is altered in RKO cells by DNA damage in a p53-dependent manner. Parental RKO and RKO-p53-KD cells were mock treated or treated with doxorubicin (DOX). These cells were then stained with anti-p53, anti-myosin VI, and DAPI.
    14. 14. Myosin VI localization in trans -Golgi is confirmed by the co-localization with the trans-Golgy marker TGN p230. H24-112 cell lines were either uninduced (control) or induced to express either p53, p73 alone or both. H24-112 cell line RKO cell line Co localization of myosin VI with trans -Golgi marker TGN p230. Parental RKO cells were mock treated or treated with nutlin or camptothecin (CPT). Immunofluorescence staining - p53 was stained green, whereas myosin VI was stained red. Nuclei were stained blue. con, control.
    15. 15. Nuclear Localization of Myosin VI is increased by p53 Myosin VI is required for efficient stabilization of p53 by DNA damage. Myo6-KD-87, in which myosin VI is inducibly knocked down by siRNA, was uninduced (-) or induced (+) to express siRNA against myosin VI for 3 days followed by treatment with 0 or 5 g/ml of doxorubicin for 0.5, 2, or 4 h . The expression level of myosin VI, p53, and -H2AX was quantified by Western blot analysis WCE - W hole C ell E xtract NE - N uclear E xtract. Nuclear localization of myosin VI is increased by p53. Whole-cell extracts (WCE) or nuclear extracts (NE) were prepared from H1299 cells uninduced or induced to express p53 . The level of myosin VI, cis -Golgi marker GM130, p53, and actin was quantified by Western blot analysis . Myosin VI Gene Knock down Attenuates the Activation of p53.
    16. 16. D M Myosin VI knock down impairs myosin VI mediated maintenance of Golgi complex integrity Intracellular localization of myosin VI and Golgi marker protein TGN p230 in Myo6-KD-87 RKO cells . RKO cells were uninduced (top panel), treated with 1.0 g/ml of doxorubicin (DOX) for 16 h (second panel), induced to express siRNA against myosin VI (third panel), or induced to express siRNA against myosin VI and treated with 1.0 g/ml of doxorubicin (bottom panel ). Immunofluorescence staining - TGN p230 was stained green, whereas myosin VI was stained red. Nuclei were stained blue.
    17. 17. Myosin VI knock down increased Doxorubicin induced apoptosis from 43 to 55% in RKO cells. Caspases are proteases that mediate apoptosis. Cleavage of caspase leads to caspase activation, whereas PARP is an essential enzyme for cell survival and its cleavage by caspase is a hallmark of apoptosis. DNA damage-induced apoptotic response is enhanced by myosin VI knockdown . Myo6-KD-87 cells which were uninduced or induced to express siRNA against myosin VI, were untreated or treated with 1.0 g per ml of doxorubicin. The expression level of myosin VI, p53, p21, PARP, caspase 8, and actin was quantified by Western blot analysis. PARP – Poly ADP Ribose Polymerase, an enzyme Involved in DNA repair.
    18. 18. ATM is a Kinase activated by DNA damage. It phosphorylate and activate p53. phosphorylated p53 is stable against the mdm2 mediated proteolysis Myosin VI Knock-down Accelerates DNA damage Induced Apoptosis Knockdown of myosin VI leads to impaired phosphorylation of p53 via ATM and increased expression of Fas, a target of p53 . Myo6-KD-87 cells, which were uninduced or induced to express siRNA against myosin VI, were untreated or treated with 1.0 g per ml of doxorubicin . The expression level target proteins was quantified by Western blot analysis.
    19. 19. Conclusions: p53 binds directly to the promoter of the myosin VI gene and transcriptionally regulates myosin VI gene expression Upon expression of p53 myosin VI is relocated from endocytic vesicles, membrane ruffles, and cytosol to the Golgi complex, perinuclear membrane, and nucleus. Since loss of myosin VI leads to increased DNA damage-induced apoptotic response, p53 has a novel function in the maintenance of Golgi complex integrity via myosin VI and that myosin VI has a novel prosurvival function in the DNA damage response pathway.

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