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The RhoA effector mDia is induced during T cell activation and regulates actin polymerization and cell migration in T
Miguel Vicente-Manzanares1, Mercedes Rey, Manuel Pérez-Martínez
1Servicio de Inmunología, Hospital de la Princesa, Universidad Autónoma de Madrid, Madrid, Spain.
Abstract:
Regulation of actin polymerization is critical for many different functions of T lymphocytes, including cell migration. Here we show that the RhoA effector mDia is induced in vitro in activated PBL and is highly expressed in vivo in diseased tissue-infiltrating activated lymphocytes. mDia localizes at the leading edge of polarized T lymphoblasts in an area immediately posterior to the leading lamella, in which its effector protein profilin is also concentrated. Overexpression of an activated mutant of mDia results in an inhibition of both spontaneous and chemokine-directed T cell motility. mDia does not regulate the shape of the cell, which involves another RhoA effector, p160 Rho-coiled coil kinase, and is not involved in integrin-mediated cell adhesion. However, mDia activation blocked CD3- and PMA-mediated cell spreading. mDia activation increased polymerized actin levels, which resulted in the blockade of chemokine-induced actin polymerization by depletion of monomeric actin. Moreover, mDia was shown to regulate the function of the small GTPase Rac1 through the control of actin availability. Together, our data demonstrate that RhoA is involved in the control of the filamentous actin/monomeric actin balance through mDia, and that this balance is critical for T cell responses.
Insights
The RhoA effector mDia regulates actin polymerization, impacting T cell migration and responses. This study reveals mDia
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Actin polymerization is crucial for T lymphocyte functions, particularly cell migration.
- The RhoA effector mDia is implicated in cellular processes.
Purpose of the Study:
- To investigate the role of mDia in T lymphocyte migration and actin dynamics.
- To elucidate the mechanism by which mDia influences T cell motility and responses.
Main Methods:
- Induction and expression analysis of mDia in activated peripheral blood lymphocytes (PBL) and diseased tissue-infiltrating lymphocytes.
- Localization studies of mDia and its effector profilin in T lymphoblasts.
- Functional assays involving overexpression of an activated mDia mutant to assess effects on T cell motility, cell spreading, and actin polymerization.
- Investigation of mDia's interaction with small GTPase Rac1.
Main Results:
- mDia is induced in activated T cells and highly expressed in vivo in activated lymphocytes within diseased tissues.
- mDia localizes at the leading edge of polarized T lymphoblasts, posterior to the leading lamella where profilin concentrates.
- Overexpression of activated mDia inhibits spontaneous and chemokine-directed T cell motility, and blocks CD3- and PMA-mediated cell spreading.
- mDia activation increases polymerized actin, leading to monomeric actin depletion and blockade of chemokine-induced actin polymerization.
- mDia regulates Rac1 function by controlling actin availability.
Conclusions:
- RhoA, via its effector mDia, controls the balance between filamentous and monomeric actin.
- This actin balance regulated by mDia is critical for T cell migration and overall T cell responses.
- mDia's role extends beyond cell shape regulation, impacting T cell motility and actin dynamics.