The surfaces of cells are covered with a dense layer (glycocalyx) of glycoproteins, glycolipids, and proteoglycans. These glycoconjugates bind to various proteins, including growth factors, enzymes, and extracellular matrix proteins, and thereby participate in a wide variety of biological phenomena related to cell differentiation, proliferation and migration, morphogenesis, and normal and pathophysiology. To a large extent these interactions are determined by the structure of the polysaccharide chains (glycans) that distinguish the various subclasses of glycoconjugates. The assembly of these molecules involves many enzymes, substrates and cofactors and differs from the assembly of nucleic acids and proteins in not requiring a template. Understanding how cells organize the assembly process to bring about cell-type specific glycans and biological responses is a major problem in modern cell biology.

Research in my lab utilizes a combination of chemistry, cell biology and genetics to understand the structure and function of sulfated glycosaminoglycans found on proteoglycans. This group of glycans consists of heparan sulfate and chondroitin/dermatan sulfate. We have numerous cell and organismal mutants altered in genes that encode the biosynthetic enzymes and the protein cores on which the chains assemble. Studies of these cell lines and mice bearing conditional and systemic mutations allow us to analyze glycan function in normal physiology and disease. Current work arranged by systems include:

  • Proteoglycan Metabolism: We have an ongoing program to characterize mouse strains lacking specific sulfotransferases and glycosyltransferases involved in heparan and chondroitin/dermatan sulfate assembly. We are also interested in lysosomal catabolism of glycosaminoglycans and the impact of defective degradation on neurodevelopment.

  • Chemical Biology of Proteoglycans: In collaboration with Y. Tor's group in the Department of Chemistry and Biochemistry, we have developed guanidinylated glycosides that bind to proteoglycans and facilitate delivery of high molecular weight cargo into the interior of the cell. In another study, a high throughput screening for small drug-like molecules that stimulate heparan sulfate synthesis is underway as a segue to developing drugs for treating hereditary multiple exostoses.

  • Lipoprotein Metabolism: Proteoglycans play important roles in lipoprotein metabolism. We defined a single proteoglycan in hepatocytes that mediates clearance of triglycerides from the circulation. We study both the receptors that mediate clearance, the apolipoproteins responsible for binding to receptors, and the role of proteoglycans in atherosclerosis.

  • Endothelial Biology: Projects in this area involve studies of proteoglycans in inflammation and bacterial infection. Another project focuses on the role of proteoglycans in receptor assembly in signaling as related to vascular biology and atherosclerosis, with particular emphasis on membrane proteins that interact with rare sulfated sequences.

The lab currently consists of 5 postdoc researchers, 5 graduate students, 2 technicians, and 10 undergraduates. We have lab meeting every week (Wednesdays at 9:30 am), a journal club focused on Current Literature in Glycobiology (BIOM 246, Fridays at noon), and periodic submeetings to coordinate projects with collaborators on and off campus. Trainees receive classical training in the chemistry and biochemistry of glycans and modern training in genetics, cell biology and physiology. My door is always open — stop by anytime.

Relevant Publications