ABL TYROSINE KINASES MEDIATE INTERCELLULAR ADHESION By
Total Page:16
File Type:pdf, Size:1020Kb
ABL TYROSINE KINASES MEDIATE INTERCELLULAR ADHESION by Nicole L. Zandy Department of Pharmacology and Cancer Biology Duke University Date:_______________________ Approved: ___________________________ Ann Marie Pendergast, Supervisor ___________________________ Christopher Counter ___________________________ Mark Dewhirst ___________________________ Christopher Kontos ___________________________ Xiao‐Fan Wang Dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Pharmacology and Cancer Biology in the Graduate School of Duke University 2008 ABSTRACT ABL TYROSINE KINASES MEDIATE INTERCELLULAR ADHESION by Nicole L. Zandy Department of Pharmacology and Cancer Biology Duke University Date:_______________________ Approved: ___________________________ Ann Marie Pendergast, Supervisor ___________________________ Christopher Counter ___________________________ Mark Dewhirst ___________________________ Christopher Kontos ___________________________ Xiao‐Fan Wang An abstract of a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor in the Department of Pharmacology and Cancer Biology in the Graduate School of Duke University 2008 Copyright by Nicole Lynn Zandy 2008 Abstract Adherens junctions are calcium‐dependent cell‐cell contacts formed during epithelial morphogenesis that link neighboring cells via cadherin receptors. Coordinated regulation of the actin cytoskeleton by the Rho GTPases is required for the formation and dissolution of adherens junctions, however the pathways that link cadherin signaling to cytoskeletal regulation remain poorly defined. The Abl tyrosine kinases been shown to modulate cytoskeletal reorganization downstream of various extracellular signals including growth factor receptors and integrins. Here we use pharmacological inhibition, genetic inactivation, and RNA interference to identify the Abl family kinases as critical mediators of cadherin‐mediated adhesion. Endogenous Abl family kinases, Abl and Arg, are activated and are required for Rac activation following cadherin engagement, and regulate the formation and maintenance of adherens junctions in mammalian cells. Significantly, we show that Abl‐ dependent regulation of the Rho‐ROCK‐myosin signaling pathway is critical for the maintenance of adherens junctions. Inhibition of the Abl kinases in epithelial sheets results in activation of Rho and its downstream target ROCK, leading to enhanced phosphorylation of the myosin regulatory light chain. These signaling events result in enhanced stress fiber formation and increased acto‐myosin contractility, thereby disrupting adherens junctions. Conversely, Arg gain‐of‐function promotes adherens iv junction formation through a Crk‐dependent pathway in cells with weak junctions. These data identify the Abl kinases as a novel regulatory link between the cadherin/catenin adhesion complex and the actin cytoskeleton through regulation of Rac and Rho during adherens junction formation. Unexpectedly, we identified a requirement for Abl and Crk downstream of Rac in the regulation of adherens junctions. Therefore, Abl functions both upstream and downstream of Rac in regulating adherens junctions, which suggests the possibility of a positive feedback loop consisting of Abl‐Crk‐Rac. Finally, we identified the Abl kinases as critical mediators of epithelial cell response to HGF. Pharmacological inhibition of Abl kinase activity resulted in impaired dissolution of adherens junctions downstream of HGF stimulation of the Met receptor. Additionally, we observed decreased phosphorylation of the Met receptor itself, along with Gab1 and Crk, downstream effectors of Met signaling. Taken together, these data suggest a requirement for Abl kinases in both adherens junctions formation and turnover. v Dedication It is with a sense of profound loss and utter desolation that I dedicate this dissertation in loving memory of my father, Leonard Marino Zandy (Sunday, August 6, 1944‐Friday, November 23, 2007). Exactly five months have passed since I lost my first valentine, my career role model, my sports buddy and “athletic” trainer, my TV gossip companion, my “project manager,” my verbal sparring partner, my first styling “client,” my inspiration to achieve without costing others and to give until it hurts, the foundation of my moral and ethical beliefs, the sun in my solar system, the center of my family, and the platinum standard I use to gauge the value of husband and father. Just two days and five months ago, I was exhausted, in part due to our trip to South Bend, but happily submitting my dissertation in plenty of time to finish dinner before watching Duke win the Maui Invitational and looking forward to seeing Santa Claus in the Macy’s Thanksgiving Day Parade the next day. On Thanksgiving Day, my dad, mom, Kim, Pam, and I sat at the table eating turkey, roast “beast,” and mashed potatoes, while Kurbain ate a cornucopia of food “donations.” It was a perfect meal. On Friday, I woke up with a headache, but insisted I would not miss our family tradition of me & mommy & daddy cutting down our Christmas tree‐I had to get it decorated before I left to return to Durham to prepare for my thesis defense the vi following week. We all got ready, went to our usual local tree farm, and almost too easily found the “perfect tree,” our first Fraser Fir from PA in years, and brought it home. The events that followed are too private to be shared: and just like that…he was gone… And in that instant, I learned infinitely more than the words that follow on these hundred‐odd pages describing five years’ work convey. It is the wisdom from that moment that I will continue to build on and share in his name. I miss you, Daddy. xoxo Love, Nicole vii Contents Abstract .........................................................................................................................................iv Dedication .....................................................................................................................................vi List of Figures ..............................................................................................................................xii 1. Introduction ...............................................................................................................................1 1.1 Adherens junctions...........................................................................................................1 1.1.1 Adherens junctions during development ................................................................1 1.1.2 Adherens junctions in cancer.....................................................................................5 1.1.3 Adherens junction components.................................................................................8 1.1.3.1 Cadherin family proteins....................................................................................8 1.1.3.2 Catenin family proteins.......................................................................................9 1.1.3.3 Actin cytoskeleton..............................................................................................11 1.1.4 Regulation of adherens junctions............................................................................13 1.1.4.1 Adherens junction component binding ..........................................................14 1.1.4.2 Phosphorylation.................................................................................................15 1.1.4.3 Rho GTPases .......................................................................................................18 1.2 Cross‐talk between Adherens junctions and Receptor Tyrosine Kinases ..............23 1.2.1 Interactions between adherens junctions and RTKs ............................................25 1.2.2 Met receptor tyrosine kinase....................................................................................29 1.2.2.1 Cancer relevance ................................................................................................29 1.2.2.2 Biological effects of Met activation..................................................................30 viii 1.2.2.3 Met signaling ......................................................................................................32 1.3 Abl family of non‐receptor Tyrosine Kinases.............................................................36 1.3.1 Abl and Arg................................................................................................................37 1.3.2 Regulation of Abl/Arg ..............................................................................................42 1.3.2.1 Physical................................................................................................................42 1.3.2.2 Protein modification ..........................................................................................44 1.3.2.3 Upstream signals regulating Abl tyrosine kinase activity ...........................45 1.3.3 Biological function of Abl/Arg ................................................................................48 1.3.3.1 In vivo roles of Abl and Arg.............................................................................48 1.3.3.2 Abl kinases regulate response to growth factors and cell migration .........50 1.3.3.3 Abl family kinases in intercellular conversations .........................................52 2. Abl Tyrosine Kinases regulate cell‐cell adhesion