title: PTEN inhibits PREX2-catalyzed activation of RAC1 to restrain tumor cell invasion.
abstract: The tumor suppressor PTEN restrains cell migration and invasion by a mechanism that is independent of inhibition of the PI3K pathway and decreased activation of the kinase AKT. PREX2, a widely distributed GEF that activates the GTPase RAC1, binds to and inhibits PTEN. We used mouse embryonic fibroblasts and breast cancer cell lines to show that PTEN suppresses cell migration and invasion by blocking PREX2 activity. In addition to metabolizing the phosphoinositide PIP₃, PTEN inhibited PREX2-induced invasion by a mechanism that required the tail domain of PTEN, but not its lipid phosphatase activity. Fluorescent nucleotide exchange assays revealed that PTEN inhibited the GEF activity of PREX2 toward RAC1. PREX2 is a frequently mutated GEF in cancer, and examination of human tumor data showed that PREX2 mutation was associated with high PTEN expression. Therefore, we tested whether cancer-derived somatic PREX2 mutants, which accelerate tumor formation of immortalized melanocytes, were inhibited by PTEN. The three stably expressed, somatic PREX2 cancer mutants that we tested were resistant to PTEN-mediated inhibition of invasion but retained the ability to inhibit the lipid phosphatase activity of PTEN. In vitro analysis showed that PTEN did not block the GEF activity of two PREX2 cancer mutants and had a reduced binding affinity for the third. Thus, PTEN antagonized migration and invasion by restraining PREX2 GEF activity, and PREX2 mutants are likely selected in cancer to escape PTEN-mediated inhibition of invasion.
authors.affiliation: Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, New York, NY 10029, USA.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Mense
authors.affiliation: Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, New York, NY 10029, USA. Department of Pharmacology, Columbia University, New York, NY 10032, USA.
authors.forename: Douglas
authors.initials: D
authors.lastname: Barrows
authors.affiliation: Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, New York, NY 10029, USA.
authors.forename: Cindy
authors.initials: C
authors.lastname: Hodakoski
authors.affiliation: Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, New York, NY 10029, USA. Integrated Program in Cellular, Molecular, Structural, and Genetic Studies, Columbia University, New York, NY 10032, USA.
authors.forename: Nicole
authors.initials: N
authors.lastname: Steinbach
authors.affiliation: Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, New York, NY 10029, USA. Integrated Program in Cellular, Molecular, Structural, and Genetic Studies, Columbia University, New York, NY 10032, USA.
authors.forename: David
authors.initials: D
authors.lastname: Schoenfeld
authors.affiliation: Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, New York, NY 10029, USA.
authors.forename: William
authors.initials: W
authors.lastname: Su
authors.affiliation: Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, New York, NY 10029, USA.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Hopkins
authors.affiliation: Herbert Irving Comprehensive Cancer Center, Columbia University, 1130 St. Nicholas Avenue, New York, NY 10032, USA.
authors.forename: Tao
authors.initials: T
authors.lastname: Su
authors.affiliation: Department of Medicine, Columbia University, 630 West 168th Street, New York, NY 10032, USA.
authors.forename: Barry
authors.initials: B
authors.lastname: Fine
authors.affiliation: Herbert Irving Comprehensive Cancer Center, Columbia University, 1130 St. Nicholas Avenue, New York, NY 10032, USA. Department of Pathology and Cell Biology, Columbia University, 630 West 168th Street, New York, NY 10032, USA.
authors.forename: Hanina
authors.initials: H
authors.lastname: Hibshoosh
authors.affiliation: Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, New York, NY 10029, USA. ramon.parsons@mssm.edu.
authors.forename: Ramon
authors.initials: R
authors.lastname: Parsons
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics / Q000502:physiology*; D017931:DNA Primers / Q000235:genetics; D005455:Fluorescent Antibody Technique; D055786:Gene Knockout Techniques; D005822:Genetic Vectors; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D016086:Lentivirus; D051379:Mice; D009361:Neoplasm Invasiveness / Q000517:prevention & control*; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D034741:RNA, Small Interfering / Q000235:genetics; D018709:Statistics, Nonparametric; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D020662:Guanine Nucleotide Exchange Factors; C490712:PREX2 protein, human; C107953:RAC1 protein, human; D034741:RNA, Small Interfering; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D020830:rac1 GTP-Binding Protein
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