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
R. B. Parker and J. J. Kohler, "Regulation of intracellular signaling by extracellular glycan remodeling" ACS Chemical Biology, in press, December 2009
Kohler JJ, "Aniline: a catalyst for sialic acid detection" Chembiochem, 10(13):2147-50, September 2009
M. M. Desko, D. A. Gross, and J. J. Kohler, "Effects of N-glycosylation on the activity and localization of GlcNAc-6-sulfotransferase 1" Glycobiology, 19(10):1068-77, October 2009
M. R. Bond, H. Zhang, P. D. Vu, and Kohler, J. J, "Photocrosslinking of glycoconjugates using metabolically incorporated diazirine-containing sugars" Nature Protocols, 4:1044-1063, June 2009
P. L. Lee, J. J. Kohler, and S. R. Pfeffer, "Association of beta-1,3-N-acetylglucosaminyltransferase 1 and beta-1,4-galactosyltransferase 1, trans-Golgi enzymes involved in coupled poly-N-acetyllactosamine synthesis" Glycobiology, 19:655-64, June 2009
SIGNIFICANT PUBLICATIONS
Y. Tanaka and J. J. Kohler, "Photoactivatable crosslinking sugars for capturing glycoprotein interactions" J. Amer. Chem. Soc., 130:3278-3279, 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
Point and right click (click and hold for Mac users) your mouse onand select "Save this link (or target) as..." option to save the file to your local computer.
