Research in my laboratory focuses on the following three areas:

1. Transporter Biology
Membrane transport proteins are key regulators of cellular uptake and homeostasis for many essential nutrients. Furthermore, transporters influence the absorption, disposition and toxicity of many drugs, and they may provide targets for novel therapeutics as well as prodrug approaches. Despite their clinical significance, most transporters are poorly characterized at the molecular level primarily due to their resistance to crystallization, thereby hampering rational drug design or prediction of drug-transporter interactions. My laboratory has developed a novel approach that combines molecular and computational biology to delineate the three-dimensional structure, ligand-binding domains, and cellular transport mechanism of transporters.

This involves the following techniques: general molecular biology and cloning; site-directed mutagenesis; substituted cysteine accessibility method (SCAM); protein expression, purification; kinetic assessment of membrane transport in cultured cells; protein trafficking.

2. Drug Delivery and Cellular Trafficking
Cellular permeability remains a crucial problem for the majority of pharmacologically active compounds under development. During the past decade it was observed that a vast amount of drugs share absorption pathways with those for nutrients and several of these transport routes are under investigation for drug delivery purposes. As a result, our knowledge about substrate specificity and structure-transport relationships has significantly increased.

My laboratory is interested in using membrane uptake systems as a drug delivery strategem. One project focuses on the cellular entry of riboflavin (vitamin B2). Our lab discovered the existence of a cell-surface receptor for this vitamin that has only recently been cloned. By functionalizing and conjugating riboflavin to polymers and other nanoparticles, we aim to optimize drug delivery to cancer cells as well as facilitate tumor imaging.

This work involves the following techniques: chemical synthesis; polymer synthesis and characterization; subcellular trafficking studies using confocal microscopy; live cell imaging; siRNA; dominant-negative constructs; small animal imaging and pharmacokinetics.

3. Computational Biology
Computational methods represent a useful tool to study the transport mechanism and substrate affinity requirements of membrane transporters. It efficiently fills the gap between our knowledge of transporter structural mechanisms at atomic level and that of transporter in vitro properties derived by biochemical experiments. This type of hybrid approach will eventually lead to the discovery of safer and more efficient drugs by targeting transporters or, in the case of efflux pumps, avoiding them for increased cellular permeability. Techniques that do not require a priori knowledge of transporter structure such as ligand-based quantitative structure-activity relationships (QSAR) can be applied to gain an understanding of how structural features impact transporter affinity. Alternatively, comparative models may be constructed for transport proteins that are homologous to or have similar membrane topology to crystallized proteins.

My laboratory is interested in developing QSAR models for efflux and uptake transporters, metabolic enzymes and nuclear receptors so as to develop a unified model for cellular drug pharmacokinetics. Furthermore, we aim to construct robust homology models for transport proteins by applying molecular dynamics using full hydration and lipid bilayer systems to simulate the movement of transporter proteins at themolecular level.

This work involves the following techniques: pharmacophore model development; homology modeling; 3D-QSAR; docking, molecular dynamics; data mining.

Publications in PubMed