Our current focus is on the process of polysialylation that is catalyzed by two polysialyltransferases (polySTs), ST8SiaII (STX) and ST8SiaIV (PST). Polysialic acid (polySia) is unique in that it is found on a small group of mammalian proteins, with the neural cell adhesion molecule (NCAM) being its major carrier. As a highly negatively charged, anti-adhesive glycan, polySia is absolutely required for proper brain development, as well as processes in the adult requiring on-going cell migration and plasticity, such as learning and memory. The up-regulation of polySia promotes neural repair and regeneration, and polySia is highly expressed on several metastatic cancer cells where it is believed to enhance their growth and invasiveness.
We are taking biochemical, structural, and cell biological approaches to understand how the polySTs specifically recognize their substrates. We have identified sequences in both NCAM and the polySTs that are required for specific recognition and polysialylation, and are expanding these studies to other substrates such as neuropilin-2 and SynCAM 1. We hope that our results will allow us to develop strategies to either enhance or block polysialylation during development, regeneration and disease.
Other interests of the lab include:
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The mechanisms underlying the Golgi localization of glycosyltransferases and nucleotide sugar transporters.
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Analysis of the structure and function of glycosyltransferases and nucleotide sugar transporters.
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The polySTs recognize an acidic surface on the FN1 domain of NCAM that positions them to polysialylate two N-glycans on the adjacent Ig5 domain. Recent results indicate that basic residues at the stem-catalytic domain border of the polySTs mediate their recognition of NCAM, SynCAM 1 and neuropilin-2. |
Selected Recent Publications
Close, B. E. and Colley, K. J. (2000) Polysialyltransferase-1autopolysialylation is not requisite for polysialylation of NCAM. J. Biol. Chem. 275, 4484-4491. Abstract
Close, B. E., Wilkinson, J. M., Bohrer, T. J., Goodwin, C. P., Broom, L. J., and Colley, K. J. (2001) The polysialyltransferase ST8Sia II/STX: Post-translational processing and role of autopolysialylation in the polysialylation of neural cell adhesion molecule. Glycobiology 11, 997-1008. Abstract
Close, B. E., Mendiratta, S.,Geiger, K., Broom, L. J., Ho, L.-L. and Colley, K. J. (2003) The minimal structural domains required for neural cell adhesion molecule polysialylation by PST/ST8Sia IV and STX/ST8Sia II. J. Biol. Chem. 278, 30796-30805. Abstract
Fenteany, F. H. and Colley, K. J. (2005) Multiple signals are required for a2, 6-sialyltransferase (ST6Gal I) oligomerization and Golgi localization. J. Biol. Chem. 280, 5423-5429. Abstract
Mendiratta, S. S., Sekulic, N., Lavie, A. and Colley, K. J. (2005) Specific amino acids in the first fibronectin type III repeat of the neural cell adhesion molecule are required for its recognition and polysialylation by and ST8Sia IV/PST. J. Biol. Chem. 280, 32340-32348. Abstract
Zhao, W., Chen, T.-L. L., Vertel, B. M. and Colley K. J. (2006) The CMP-sialic acid transporter is localized in the medial-trans Golgi and possesses two specific endoplasmic reticulum export motifs in its carboxy-terminal cytoplasmic tail. J. Biol. Chem. 281, 31106-31118. Abstract
Mendiratta, S. S., Sekulic, N., Hernandez-Guzman, F. G., Close, B. E., Lavie, A. and Colley, K. J. (2006) A novel a-helix in the first fibronectin type III repeat of the neural cell adhesion molecule is critical for N-glycan polysialylation.J. Biol. Chem.281, 36052-36059. Abstract
Foley, D., Swartzentruber, K. G., and Colley, K. J. (2009) Identification of sequences in the polysialyl-transferases, ST8Sia II and ST8Sia IV, required for the protein specific polysialylation of the neural cell adhesion molecule, NCAM. J. Biol. Chem.284, 15505-15516. Abstract
Foley, D. A., Swartzentruber, K. G., Lavie, A., and Colley, K. J. (2010). Structure and mutagenesis of neural cell adhesion molecule domains: evidence for flexibility in the placement of polysialic acid attachment sites. J. Biol. Chem. 285, 27360-27371. Abstract
Foley, D. A., Swartzentruber, K. G., Thompson, M. G., Mendiratta, S. S., and Colley, K. J. (2010) Sequences from the first fibronection type III repeat of the neural cell adhesion molecule allow O-glycan polysialylation of an adhesion molecule chimera. J. Biol. Chem. 285, 35056-35067. Abstract
Thompson, M. G., Foley, D. A., Swartzentruber, K. G., and Colley, K. J. (2011) Sequences at the interface of the fifth immunoglobulin domain and first fibronectin type III repeat of the neural cell adhesion molecule are critical for its polysialylation. J. Biol. Chem. 286, 4525-4534. Abstract
Zapater, J. L. and Colley, K. J. (2011) Sequences prior to conserved catalytic motifs of the polysialyltransferase, ST8SiaIV, are required for substrate recognitionJ. Biol. Chem., in press. jbc.M111.322024. doi:10.1074/jbc.M111.322024. Abstract |
