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PI3-kinase p110 alpha mediates beta 1 integrin-induced Akt activation and membrane protrusion during cell attachment and initial spreading
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
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2010 (English)In: Cellular Signalling, ISSN 0898-6568, E-ISSN 1873-3913, Vol. 22, no 12, 1838-1848 p.Article in journal (Refereed) Published
Abstract [en]

Integrin-mediated cell adhesion activates several signaling effectors, including phosphatidylinositol 3-kinase (PI3K), a central mediator of cell motility and survival. To elucidate the molecular mechanisms of this important pathway the specific members of the PI3K family activated by different integrins have to be identified. Here, we studied the role of PI3K catalytic isoforms in beta 1 integrin-induced lamellipodium protrusion and activation of Akt in fibroblasts. Real-time total internal reflection fluorescence imaging of the membrane substrate interface demonstrated that beta 1 integrin-mediated attachment induced rapid membrane spreading reaching essentially maximal contact area within 5-10 min. This process required actin polymerization and involved activation of PI3K. Isoform-selective pharmacological inhibition identified p110 alpha as the PI3K catalytic isoform mediating both beta 1 integrin-induced cell spreading and Akt phosphorylation. A K756L mutation in the membrane-proximal part of the beta 1 integrin subunit, known to cause impaired Akt phosphorylation after integrin stimulation, induced slower cell spreading. The initial beta 1 integrin-regulated cell spreading as well as Akt phosphorylation were sensitive to the tyrosine kinase inhibitor PP2, but were not dependent on Src family kinases, FAK or EGF/PDGF receptor transactivation. Notably, cells expressing a Ras binding-deficient p110 alpha mutant were severely defective in integrin-induced Akt phosphorylation, but exhibited identical membrane spreading kinetics as wild-type p110 alpha cells. We conclude that p110 alpha mediates beta 1 integrin-regulated activation of Akt and actin polymerization important for survival and lamellipodia dynamics. This could contribute to the tumorigenic properties of cells expressing constitutively active p110 alpha.

Place, publisher, year, edition, pages
2010. Vol. 22, no 12, 1838-1848 p.
Keyword [en]
beta 1 integrin, PI3K, p110 alpha, Cell spreading, Akt
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-134169DOI: 10.1016/j.cellsig.2010.07.011ISI: 000282857200006OAI: oai:DiVA.org:uu-134169DiVA: diva2:371816

Correction in: Cellular signaling, vol. 24, issue 4, p: 971-972, DOI: 10.1016/j.cellsig.2011.12.010

Available from: 2010-11-22 Created: 2010-11-22 Last updated: 2012-04-19Bibliographically approved
In thesis
1. Integrin Signaling in Cell Adhesion and Mechanotransduction: Regulation of PI3K, AKT, and ROS
Open this publication in new window or tab >>Integrin Signaling in Cell Adhesion and Mechanotransduction: Regulation of PI3K, AKT, and ROS
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Integrins are a family of conserved cell surface receptors found throughout the animal kingdom. They comprise 24 dimers in mammals, and regulate a number of processes including cell survival, differentiation, and migration. These complex cellular responses involve processes such as cell attachment, spreading, and various signaling pathways, which in turn depend on the composition of the extracellular environment, on its mechanical properties, and involved integrin types. This thesis focuses on identifying molecules that signal downstream of integrins and how integrin-induced signals may differ dependent on the type of mechanical stimulus that is given.

In Paper I, we show that cell spreading and the activation of AKT is regulated by the catalytic PI3K isoform p110α. An intact β1 integrin cytoplasmic tail and actin polymerization was needed for spreading, whereas the presence of FAK or SRC, or the interaction between p110α and RAS was dispensable.

Paper II reports that the RICTOR-mTOR complex (TORC2) acts as the kinase downstream of β1 integrins in order to phosphorylate AKT on Ser473, which was functionally linked to cell survival. β1 integrins activated both AKT1 and AKT2, but seemed to prefer AKT2. The investigation of several receptor types with regard to their requirement of TORC2, PAK, and ILK for AKT Ser473 phosphorylation revealed that different kinds of receptors engage specific enzyme combinations depending on cell type and context.

In the third paper, we demonstrate that adhesion- and mechanical stretch-induced integrin signaling lead to divergent protein phosphorylation patterns, and that most signals from cell adhesion were not dependent on intracellular contractility. This indicates that integrin ligand binding and mechanical stretch induce signaling via distinct mechanisms. Reactive oxygen species (ROS) derived from different cellular sources modulated these responses. Stretching primarily induced phosphorylation of ERK1/2, and this signal was markedly increased by a derivative of the antioxidant ascorbate and extracellularly administered catalase. The robust AKT phosphorylation in response to adhesion was almost completely abolished with an inhibitor targeting mitochondrial ROS, whereas phosphorylation levels were only marginally affected in stretch assays. Similar results were obtained with siRNA knock-down of a critical subunit of ROS-producing NADPH oxidases.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 46 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 750
integrin, ROS, PI3K, AKT, mechanosignaling, actin polymerization, spreading
National Category
Cell and Molecular Biology
urn:nbn:se:uu:diva-170267 (URN)978-91-554-8301-2 (ISBN)
Public defence
2012-04-27, C10:301, BMC, Husargatan 3, Uppsala, 10:00 (English)
Available from: 2012-04-04 Created: 2012-03-09 Last updated: 2012-04-19Bibliographically approved

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Zeller, Kathrin S.Velling, TeetTengholm, AndersJohansson, Staffan
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