Chung Lab >> Home
Welcome!
Chung, Chang Y., Ph. D.
Assistant Professor of Pharmacology
Vanderbilt University Medical Center
468 Robinson Research Building
Nashville, TN 37232-6600
Tel. (615) 322-4956
chang.chung@vanderbilt.edu
Chemotaxis of cells toward a micropipette emitting cAMP. Redistribution of N-PAK-GFP in a living cell upon loss of cellular polarity
Research
The goal of our laboratory is to understand signaling pathways regulating cell polarity and motility during chemotaxis. Chemotaxis, directed movement towards a chemoattractant agent, is essential for many biological processes such as immune responses, wound healing, axon guidance, and the development of Dictyostelium. The binding of extracellular ligands to cell surface receptors leads to the directed reorganization of the actin and myosin cytoskeletons, pseudopod extension in the direction of the chemoattractant source, and cell movement via signaling pathways that are highly conserved among species.
Dictyostelium cells provide a powerful system to examine the role of cellular components to control coordinated cell movement because of the ability to apply genetic as well as cell biological approaches. Studies have shown that the conserved nature of many signaling systems in yeast, Dictyostelium, and mammalian cells allow the regulatory pathways identified in Dictyostelium to be of significance for research into the control of cell motility and chemotaxis in higher eukaryotes.
Regulation of PI3 Kinase (PI3K) and PTEN: Polarized Dictyostelium cells and leukocytes can detect and respond to a very shallow chemoattractant gradient, indicating that cells must be able to sense the spatial gradient and locally activate signaling events leading cell polarity and the formation of the leading edge. Activation of phosphatidylinositol 3¿ kinase (PI3K) appears to be an essential step for establishing the initial asymmetry. Activation of PTEN, a phosphatase that removes the 3-phosphate from the PI3K products PI(3,4,5)P3 at the lateral membrane and PAKa at the uropod appears to be key components for the global inhibition. We are trying to identify genes involved in the translocation of PI3K to the membrane by performing high-throughput screening of REMI (Restriction Enzyme Mediated Insertion) mutants with automated flu
orescence microscopy. We are also studying spatial and temporal dynamics of signaling components of local activation and global inhibition (e.g. PI3K, PTEN, PKB, and PAKa) using microfluidics gradient chamber and microscopy.
Establishment of polarized cytoskeleton and force generation in chemotaxing cells: An important biological question is how cells regulate the formation of the leading edge in the direction of a chemoattractant source. Dissecting signaling mechanisms controlling F-actin organization would be a key step toward understanding the directed cell movement. The Wiskott-Aldrich Syndrome protein (WASP) and related proteins have emerged as key downstream components converging on mul
tiple signaling pathways to F-actin polymerization. We are studying the role of WASP in controlling cell polarity and motility during chemotaxis by focusing on the role of B domain and its interaction with phosphoinositides. We will identify SH3 domain-containing proteins interacting with poly-proline region of WASP and identify their roles in
controlling functions of WASP. We will quantitatively measure forces generated at the leading edge and uropod by using bed-of nails microfluidics chamber and the effects of various signaling molecules on the generation of these forces will be elucidated by examining cells lacking important components (e.g. WASP and PAKa).