Cell surface carbohydrates are essential components of myriad cell-cell, cell-ligand, and cell-pathogen recognition events. Glycan-dependent binding events are implicated in a wide variety of developmental, immunological, and metastatic processes. Despite these indispensible roles, identification and characterization of glycan-mediated binding events remains challenging, due to the transient and low-affinity nature of individual interactions. My research group is developing two complementary techniques to discover and study the interactions between glycoconjugates and their binding partners. In the Golgi two-hybrid method, we are adapting traditional two-hybrid technology for use in the secretory pathway of eukaryotic cells, where it can be used to study the interactions of glycosylated proteins. In a complementary chemical approach, we are developing the use of "photo-sugars." These monosaccharides, which contain photocrosslinking groups, can be metabolically incorporated into cellular glycoconjugates where they are used to capture transient interactions.
We also study the molecular foundations of glycoconjugate synthesis. In eukaryotic cells, the organelles of the secretory pathway - the endoplasmic reticulum and the Golgi compartment - orchestrate cell surface glycosylation. The set of carbohydrates synthesized by a cell is determined by the spatial distribution of glycosyltransferases and other modifying enzymes within the Golgi cisternae; this arrangement forms an assembly line for glycoprotein and glycolipid biosynthesis. As a complicated machine responsible for task of glycosylation, the mammalian secretory pathway presents a puzzle to be solved, but also a robust biosynthetic power to be harnessed. One of my lab’s major research efforts is to obtain a molecular understanding of the processes by which Golgi enzymes select their substrates and coordinate their activities to direct the synthesis of complex carbohydrate structures. We use biochemical and biophysical studies combined with cellular and functional assays to achieve a detailed understanding of how Golgi residents work together to form the glycosylation machinery. Three inter-related questions are paramount: (a) what dictates localization to particular Golgi sub-compartments? (b) is oligomerization required for localization, catalysis, or both? (c) what are the determinants of substrate selectivity?
RESEARCH INTERESTS
carbohydrates
glycobiology
Golgi
membrane proteins
chemical biology
RECENT PUBLICATIONS
M. M. Desko and J. J. Kohler, "Glycosylation of proteins in the Golgi apparatus" Wiley Encyclopedia of Chemical Biology, in press
J. W. Chin and J. J. Kohler, "Current and future prospects in biopolymer chemistry" Curr. Op. Chem. Biol., 11:626-627, 2007
J. J. Kohler, "Chemical biology meets networks" Nat. Chem. Biol., 3:528-529, 2007
M. R. Bond and J. J. Kohler, "Chemical methods for glycoprotein discovery" Curr. Op. Chem. Biol., 11:52-58, 2007
D. H. Dube, C. L. de Graffenried, and J. J. Kohler, "Regulating cell surface glycosylation with a small molecule switch" Methods in Enzymology, 415:213-229, 2006
SIGNIFICANT PUBLICATIONS
Y. Tanaka and J. J. Kohler, "Photoactivatable crosslinking sugars for capturing glycoprotein interactions" J. Amer. Chem. Soc., in press 2008
J. J. Kohler and C. R. Bertozzi, "Regulating cell surface glycosylation by small molecule control of enzyme localization" Chemistry and Biology, 10:1303-1311, 2003
J. J. Kohler, S. J. Metallo, T. L. Schneider, and A. Schepartz, "Enhanced DNA specificity achieved by sequential binding of protein monomers" Proc. Natl. Acad. Sci. USA, 96:11735-11739, 1999
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