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Title:Molecular signaling programs underlying neutrophil polarity and chemotaxis
Author(s):Cook, Sara
Director of Research:Wang, Fei
Doctoral Committee Chair(s):Chen, Jie
Doctoral Committee Member(s):Wang, Fei; Bellini, Michel; Brieher, William M.; Tapping, Richard I.
Department / Program:Cell & Developmental Biology
Discipline:Cell and Developmental Biology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Neutrophil
Chemotaxis
Cell Migration
Neutrophil Polarity
Neutrophil Chemotaxis
Neutrophil Migration
Molecular Signaling
Protein tyrosine kinase 2 (Pyk2)
Focal Adhesion Kinase (FAK)
Filamentous Actin
Cell Signaling
Abstract:Neutrophils adopt a highly polarized morphology and integrate many matrix-specific signals to undergo specialized migratory events to pursue invading pathogens. While these matrix-specific signaling events have emerged as crucial elements for proper migration and recruitment of neutrophil cells, the underlying signaling networks remain poorly defined. We have identified Pyk2, a FAK (focal adhesion kinase) family non-receptor tyrosine kinase, as a beta2-integrin-dependent regulator of rear contraction in migrating neutrophil cells. We show that Pyk2 is specifically activated by beta2-integrin and that Pyk2 mediates contraction by interaction with p190RhoGEF and RhoA thereby regulating the myosin contractility at the rear of the cell. These data elucidate a novel mechanism in which Pyk2 integrates matrix-specific substrate interaction with the signaling network responsible for the polarized morphology needed for neutrophil migration. Another crucial component of neutrophil migration that is not fully understood is the mechanism that governs actin cytoskeleton dynamics and assembly in neutrophils. The asymmetric accumulation of filamentous actin (F-actin) at the leading edge provides the driving force for protrusion and is essential for the development and maintenance of neutrophil polarity. By using neutrophil-like HL-60 cells, we describe a pivotal role for Rictor, a component of Mammalian Target of Rapamycin Complex 2 (mTORC2), in regulating assembly of the actin cytoskeleton during neutrophil chemotaxis. Depletion of Mammalian Target of Rapamycin (mTOR) and Rictor, but not Raptor, impairs actin polymerization, leading edge establishment and directional migration in neutrophils stimulated with chemoattractants. Intriguingly, depletion of mSin1, an integral component of mTORC2, causes no detectable defects in neutrophil polarity and chemotaxis. In addition, experiments with chemical inhibition and kinase-dead mutants indicate that mTOR kinase activity and AKT phosphorylation are dispensable for chemotaxis. Instead, our results suggest that the small Rho GTPases Rac and Cdc42 serve as the downstream effectors of Rictor to regulate actin assembly and organization in neutrophils. Together, our findings reveal an mTORC2- and mTOR kinase -independent function and mechanism of Rictor in the regulation of neutrophil chemotaxis.
Issue Date:2014-01-16
URI:http://hdl.handle.net/2142/46576
Rights Information:Copyright 2013 Sara Cook
Date Available in IDEALS:2014-01-16
Date Deposited:2013-12


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