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TSC1 Controls Distribution of Actin Fibers through Its Effect on Function of Rho Family of Small GTPases and Regulates Cell Migration and Polarity

The tumor-suppressor genes TSC1 and TSC2 are mutated in tuberous sclerosis, an autosomal dominant multisystem disorder. The gene products of TSC1 and TSC2 form a protein complex that inhibits the signaling of the mammalian target of rapamycin complex1 (mTORC1) pathway. mTORC1 is a crucial molecule i...

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Autores principales: Ohsawa, Maki, Kobayashi, Toshiyuki, Okura, Hidehiro, Igarashi, Takashi, Mizuguchi, Masashi, Hino, Okio
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2013
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3552859/
https://www.ncbi.nlm.nih.gov/pubmed/23355874
http://dx.doi.org/10.1371/journal.pone.0054503
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author Ohsawa, Maki
Kobayashi, Toshiyuki
Okura, Hidehiro
Igarashi, Takashi
Mizuguchi, Masashi
Hino, Okio
author_facet Ohsawa, Maki
Kobayashi, Toshiyuki
Okura, Hidehiro
Igarashi, Takashi
Mizuguchi, Masashi
Hino, Okio
author_sort Ohsawa, Maki
collection PubMed
description The tumor-suppressor genes TSC1 and TSC2 are mutated in tuberous sclerosis, an autosomal dominant multisystem disorder. The gene products of TSC1 and TSC2 form a protein complex that inhibits the signaling of the mammalian target of rapamycin complex1 (mTORC1) pathway. mTORC1 is a crucial molecule in the regulation of cell growth, proliferation and survival. When the TSC1/TSC2 complex is not functional, uncontrolled mTORC1 activity accelerates the cell cycle and triggers tumorigenesis. Recent studies have suggested that TSC1 and TSC2 also regulate the activities of Rac1 and Rho, members of the Rho family of small GTPases, and thereby influence the ensuing actin cytoskeletal organization at focal adhesions. However, how TSC1 contributes to the establishment of cell polarity is not well understood. Here, the relationship between TSC1 and the formation of the actin cytoskeleton was analyzed in stable TSC1-expressing cell lines originally established from a Tsc1-deficient mouse renal tumor cell line. Our analyses showed that cell proliferation and migration were suppressed when TSC1 was expressed. Rac1 activity in these cells was also decreased as was formation of lamellipodia and filopodia. Furthermore, the number of basal actin stress fibers was reduced; by contrast, apical actin fibers, originating at the level of the tight junction formed a network in TSC1-expressing cells. Treatment with Rho-kinase (ROCK) inhibitor diminished the number of apical actin fibers, but rapamycin had no effect. Thus, the actin fibers were regulated by the Rho-ROCK pathway independently of mTOR. In addition, apical actin fibers appeared in TSC1-deficient cells after inhibition of Rac1 activity. These results suggest that TSC1 regulates cell polarity-associated formation of actin fibers through the spatial regulation of Rho family of small GTPases.
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spelling pubmed-35528592013-01-25 TSC1 Controls Distribution of Actin Fibers through Its Effect on Function of Rho Family of Small GTPases and Regulates Cell Migration and Polarity Ohsawa, Maki Kobayashi, Toshiyuki Okura, Hidehiro Igarashi, Takashi Mizuguchi, Masashi Hino, Okio PLoS One Research Article The tumor-suppressor genes TSC1 and TSC2 are mutated in tuberous sclerosis, an autosomal dominant multisystem disorder. The gene products of TSC1 and TSC2 form a protein complex that inhibits the signaling of the mammalian target of rapamycin complex1 (mTORC1) pathway. mTORC1 is a crucial molecule in the regulation of cell growth, proliferation and survival. When the TSC1/TSC2 complex is not functional, uncontrolled mTORC1 activity accelerates the cell cycle and triggers tumorigenesis. Recent studies have suggested that TSC1 and TSC2 also regulate the activities of Rac1 and Rho, members of the Rho family of small GTPases, and thereby influence the ensuing actin cytoskeletal organization at focal adhesions. However, how TSC1 contributes to the establishment of cell polarity is not well understood. Here, the relationship between TSC1 and the formation of the actin cytoskeleton was analyzed in stable TSC1-expressing cell lines originally established from a Tsc1-deficient mouse renal tumor cell line. Our analyses showed that cell proliferation and migration were suppressed when TSC1 was expressed. Rac1 activity in these cells was also decreased as was formation of lamellipodia and filopodia. Furthermore, the number of basal actin stress fibers was reduced; by contrast, apical actin fibers, originating at the level of the tight junction formed a network in TSC1-expressing cells. Treatment with Rho-kinase (ROCK) inhibitor diminished the number of apical actin fibers, but rapamycin had no effect. Thus, the actin fibers were regulated by the Rho-ROCK pathway independently of mTOR. In addition, apical actin fibers appeared in TSC1-deficient cells after inhibition of Rac1 activity. These results suggest that TSC1 regulates cell polarity-associated formation of actin fibers through the spatial regulation of Rho family of small GTPases. Public Library of Science 2013-01-23 /pmc/articles/PMC3552859/ /pubmed/23355874 http://dx.doi.org/10.1371/journal.pone.0054503 Text en © 2013 Ohsawa et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Ohsawa, Maki
Kobayashi, Toshiyuki
Okura, Hidehiro
Igarashi, Takashi
Mizuguchi, Masashi
Hino, Okio
TSC1 Controls Distribution of Actin Fibers through Its Effect on Function of Rho Family of Small GTPases and Regulates Cell Migration and Polarity
title TSC1 Controls Distribution of Actin Fibers through Its Effect on Function of Rho Family of Small GTPases and Regulates Cell Migration and Polarity
title_full TSC1 Controls Distribution of Actin Fibers through Its Effect on Function of Rho Family of Small GTPases and Regulates Cell Migration and Polarity
title_fullStr TSC1 Controls Distribution of Actin Fibers through Its Effect on Function of Rho Family of Small GTPases and Regulates Cell Migration and Polarity
title_full_unstemmed TSC1 Controls Distribution of Actin Fibers through Its Effect on Function of Rho Family of Small GTPases and Regulates Cell Migration and Polarity
title_short TSC1 Controls Distribution of Actin Fibers through Its Effect on Function of Rho Family of Small GTPases and Regulates Cell Migration and Polarity
title_sort tsc1 controls distribution of actin fibers through its effect on function of rho family of small gtpases and regulates cell migration and polarity
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3552859/
https://www.ncbi.nlm.nih.gov/pubmed/23355874
http://dx.doi.org/10.1371/journal.pone.0054503
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