Allen Liu

Mechanical and biochemical regulation of clathrin-mediated endocytosis

Clathrin-mediated endoctyosis (CME) maintains cellular and organismal homeostasis by mediating the uptake of nutrients and controlling the expression and activity of signaling receptors. The fundamental functional unit of CME is a clathrin-coated pit (CCP) and the dynamic behavior of CCPs has been observed to be highly heterogeneous. We are interested in how mechanical and chemical stimuli affect the behavior of CCP internalization. With respect to the latter we seek to define the biochemical regulation of activated chemokine receptor CXCR4 internalization, with the long term goal of understanding the dynamics of membrane trafficking and signaling during cell motility. The combination of total internal reflection fluorescence microscopy (TIR-FM) and computational analysis under controlled mechanical and biochemical perturbations represents a powerful approach to understand what regulates the formation of individual CCPs.

GPCR dimerization

Chemotaxis of lymphocytes, which relies on a large number of chemokine receptors, plays a crucial role in the pathophysiology of cardiovascular diseases. However, how and whether interactions between different chemokine receptors might regulate cell migration is unclear. We will use a novel assay based on enzyme-based proximity biotinylation to study the homo-dimerization and hetero-dimerization of CXCR4, CCR2, and CCR5. We hope this study will yield important insights into the role of receptor dimerization in signaling as well as potentially provide a platform for screening compounds that will perturb receptor functions.

Building artificial platelets

Our vision in this project is based on the belief that the critical accumulation of our knowledge about individual biomolecules will enable us to integrate them into a system in a meaningful way to create cellular devices. We have identified platelets as a tractable biological system to emulate through modular design. Our design strategy necessitates an understanding of the functionalities of natural platelets so that our artificial platelets can confer the essential functions of natural platelets. The platelets will be made as lipid vesicles that have defined lipid and protein composition using microfluidic jetting, a technique that is akin to blowing a bubble. We hopethis study will highlight how synthetic biology can potentially bring aboutnovel cellular devices that have tremendous benefits in medical settings.

Research Areas(s)

• Systems biology
• Synthetic biology
• Cytoskeleton dynamics
• Membrane organization
• Cellular biophysics

Award(s)

• NIH Director’s New Innovator Award (2012)
• Leukemia and Lymphoma Society Fellowship (2009)