Roles of POPX2 phosphatase in the regulation of apoptosis

TGF-β activated kinase 1 (TAK1) is a MAPK kinase kinase that has emerged as an important regulator in immune response, embryo development, tumorigenesis and cell death. In this study, we have identified TAK1 as a potential target of POPX2 by pull-down mass spectrometry. POPX2 is a PP2C family serine...

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Main Author: Weng, Ting
Other Authors: Koh Cheng Gee
Format: Theses and Dissertations
Language:English
Published: 2015
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Online Access:http://hdl.handle.net/10356/62255
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-622552023-02-28T18:50:57Z Roles of POPX2 phosphatase in the regulation of apoptosis Weng, Ting Koh Cheng Gee School of Biological Sciences DRNTU::Science::Biological sciences TGF-β activated kinase 1 (TAK1) is a MAPK kinase kinase that has emerged as an important regulator in immune response, embryo development, tumorigenesis and cell death. In this study, we have identified TAK1 as a potential target of POPX2 by pull-down mass spectrometry. POPX2 is a PP2C family serine/threonine phosphatase. Association of TAK1 with POPX2 is confirmed by co-immunoprecipitation assay. An in vitro binding assay further indicates direct interaction between POPX2 and TAK1. We have found that POPX2 negatively regulates the activity of TAK1, which promotes genotoxic stress-induced apoptosis in response to VP-16. Increased activity of TAK1 in POPX2-knockdown cells results in increased IKKβ activity and subsequent transcription of anti-apoptotic genes mediated by NF-κB, thus contributing to resistance to genotoxin. In addition, we also investigated the influence of matrix stiffness in cancer progression. The rigidity of matrix plays crucial roles in tumorigenesis. Physical signals provided by the substrates are sensed and conveyed by focal adhesions and actin cytoskeletons to the interior of the cell to elicit responses. Since POPX2 has been implicated in the regulation of stress fibers and focal adhesions, the phosphatase may affect responses of cancer cells to the surrounding environment. By culturing cancer cells on polyacrylamide gels of different rigidities, we found a positive correlation between increased cell spreading and enhanced formation of stress fibers. We also observed increased number of focal adhesions with increased substrate stiffness. Interestingly, POPX2 may regulate cell response to matrix stiffness by promoting cell spreading, formation of stress fibers and focal adhesions. Apart from regulating cell morphology, higher substrate stiffness also increases cell growth. This is partly due to higher rigidity-dependent mitogenic activities of FAK, ERK, STAT3 and less basal apoptosis. Moreover, cells with reduced POPX2 levels induced by siRNA show higher growth and are more resistant to genotoxin. ​Doctor of Philosophy (SBS) 2015-03-11T03:03:49Z 2015-03-11T03:03:49Z 2014 2014 Thesis Weng, T. (2014). Roles of POPX2 phosphatase in the regulation of apoptosis. Doctoral thesis, Nanyang Technological University, Singapore. http://hdl.handle.net/10356/62255 en 119 p. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic DRNTU::Science::Biological sciences
spellingShingle DRNTU::Science::Biological sciences
Weng, Ting
Roles of POPX2 phosphatase in the regulation of apoptosis
description TGF-β activated kinase 1 (TAK1) is a MAPK kinase kinase that has emerged as an important regulator in immune response, embryo development, tumorigenesis and cell death. In this study, we have identified TAK1 as a potential target of POPX2 by pull-down mass spectrometry. POPX2 is a PP2C family serine/threonine phosphatase. Association of TAK1 with POPX2 is confirmed by co-immunoprecipitation assay. An in vitro binding assay further indicates direct interaction between POPX2 and TAK1. We have found that POPX2 negatively regulates the activity of TAK1, which promotes genotoxic stress-induced apoptosis in response to VP-16. Increased activity of TAK1 in POPX2-knockdown cells results in increased IKKβ activity and subsequent transcription of anti-apoptotic genes mediated by NF-κB, thus contributing to resistance to genotoxin. In addition, we also investigated the influence of matrix stiffness in cancer progression. The rigidity of matrix plays crucial roles in tumorigenesis. Physical signals provided by the substrates are sensed and conveyed by focal adhesions and actin cytoskeletons to the interior of the cell to elicit responses. Since POPX2 has been implicated in the regulation of stress fibers and focal adhesions, the phosphatase may affect responses of cancer cells to the surrounding environment. By culturing cancer cells on polyacrylamide gels of different rigidities, we found a positive correlation between increased cell spreading and enhanced formation of stress fibers. We also observed increased number of focal adhesions with increased substrate stiffness. Interestingly, POPX2 may regulate cell response to matrix stiffness by promoting cell spreading, formation of stress fibers and focal adhesions. Apart from regulating cell morphology, higher substrate stiffness also increases cell growth. This is partly due to higher rigidity-dependent mitogenic activities of FAK, ERK, STAT3 and less basal apoptosis. Moreover, cells with reduced POPX2 levels induced by siRNA show higher growth and are more resistant to genotoxin.
author2 Koh Cheng Gee
author_facet Koh Cheng Gee
Weng, Ting
format Theses and Dissertations
author Weng, Ting
author_sort Weng, Ting
title Roles of POPX2 phosphatase in the regulation of apoptosis
title_short Roles of POPX2 phosphatase in the regulation of apoptosis
title_full Roles of POPX2 phosphatase in the regulation of apoptosis
title_fullStr Roles of POPX2 phosphatase in the regulation of apoptosis
title_full_unstemmed Roles of POPX2 phosphatase in the regulation of apoptosis
title_sort roles of popx2 phosphatase in the regulation of apoptosis
publishDate 2015
url http://hdl.handle.net/10356/62255
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