Research In the Lab
Cell surface receptors mediate the transfer of information between cells and their environment. As a result, receptors play vital roles in all aspects of cell biology including development, immune response, homeostasis, and pharmacology. Although many receptor systems have been intensely studied, fundamental questions about their molecular function remain unanswered. Research in our group uses chemical biology to improve our mechanistic understanding of membrane biology. Specific areas of research include:
Glycolipids are a critical structural feature of the plasma membrane. In addition to biosynthetic pathways, glycolipids content is regulated by glycosyl hydrolases at the membrane. Our group has been investigating the role of the membrane-associated neuraminidase (NEU3).
Using a recombinant form of the protein, we have modeled the active site of the protein, and are working to develop specific inhibitors (Albohy, 2010). Projects in the lab continue to examine inhibition, substrate specificity, and biological function of the human neuraminidase family (Zou, 2010). Related projects are testing the role of glycosylation in the function of integrin receptors.
Lipid and glycoprotein labeling strategies
Chemists are uniquely qualified to develop new probes for biomolecular systems. We are applying new chemical methods to label specific receptors in live cells. Labeling strategies we are currently developing involve targeting membrane lipids (Sandbhor, 2009), glycoproteins (Loka, 2010a), surfaces (Loka, 2010b), and enzymes(Key, 2011).
Synthetic Lipid Probes
Membrane lipids are not only structural components of the bilayer, but also serve a role as signaling molecules. Using chemical synthesis, we are developing modified lipids which can be used to detect the location and chemical modification of sphingolipids and glycolipids (Sandbhor, 2009). Ongoing work is aimed at using these tools to probe membranes of live cells using fluorescence microscopy.
Phosphorylation is a prevalent post-translational modification in human cells. Phosphorylation is carried out by kinases, and removed by phosphatase enzymes - forming a regulatory cycle. Our group is developing chemical strategies to inhibit and specifically label phosphatase enzymes. Current targets include the receptor-like tyrosine phosphatase, CD45 (Tulsi, 2010).
Insight into biophysical mechanisms requires quantitative methods for observing biomolecules. We use observations of receptor motion (lateral mobility) in the plasma membrane as a tool to visualize biochemical events(Cairo, 2010). When appropriately labeled, the trajectories of single receptors can be observed and used to understand the types of interactions the receptor engages in. This methodology is highly dependent on effective labeling strategies - and can allow the visualization of nanoscale organization in the membrane. We have recently developed a new analytical method to identify the size of receptor clusters in the membrane using SPT (Rajani, 2011).