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Title page for ETD etd-06182012-165410


Type of Document Dissertation
Author Broussard, Joshua Allen
URN etd-06182012-165410
Title The adaptor protein APPL1 regulates cell migration and adhesion dynamics
Degree PhD
Department Biological Sciences
Advisory Committee
Advisor Name Title
Katherine L. Friedman Committee Chair
Christopher J. Janetopoulos Committee Member
Donna J. Webb Committee Member
Irina Kaverina Committee Member
James R. Goldenring Committee Member
Lilianna Solnica-Krezel Committee Member
Keywords
  • Adhesion Dynamics
  • Cell Migration
  • Akt activation
  • APPL1
  • Src signaling
Date of Defense 2012-05-04
Availability unrestricted
Abstract
Cell migration is a complex process that requires the coordination of signaling events that take place in distinct locations within the cell. Adaptor proteins are emerging as key modulators of spatially integrated processes because of their ability to localize to different subcellular compartments and bring together important signaling proteins at these sites. However, the role that adaptor proteins play in regulating cell migration is not well understood. Here, we show a novel function for the adaptor protein containing a pleckstrin homology (PH), phosphotyrosine binding (PTB), and leucine zipper motif 1 (APPL1) in modulating cell migration. APPL1 impairs the turnover of adhesions at the leading edge of cells thereby inhibiting their migration. The ability of APPL1 to impair migration is dependent on its PTB domain, which interacts with Akt, suggesting the interaction of APPL1 with Akt is important for its effect on migration. Interestingly, APPL1 decreases the amount of active Akt in cells. We show that APPL1 modulates migration and adhesion dynamics via a mechanism that involves regulation of Akt function. Src has been shown to regulate Akt function through the phosphorylation of two Akt tyrosine residues, and intriguingly, we have found that APPL1 reduces Src-mediated tyrosine phosphorylation of Akt. Therefore, we propose a model in which APPL1 regulates adhesion dynamics and cell migration by altering Src-mediated tyrosine phosphorylation of Akt. Our results further underscore the importance of adaptor proteins in modulating the flow of information through signaling pathways by demonstrating a critical new function for APPL1 in regulating cell migration and adhesion turnover.

In addition, we provide the first comprehensive phosphorylation map of APPL1. Using mass spectrometry, we identify 13 phosphorylated residues within APPL1. Four of these sites are located in important functional domains; one within the BAR domain, two cluster near the edge of the PH domain, and one within the PTB domain. These phosphorylation sites may control APPL1 function by regulating the ability of APPL1 domains to interact with other proteins and membranes.

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