Glypicans are multifunctional cell surface proteoglycans involved in several important cellular signaling pathways. Glypican-1 (Gpc1) is the predominant heparan sulfate proteoglycan in the developing and adult human brain. The two N-linked glycans and the C-terminal domain that attach the core protein to the cell membrane are not resolved in the Gpc1 crystal structure ...
Glypicans are multifunctional cell surface proteoglycans involved in several important cellular signaling pathways. Glypican-1 (Gpc1) is the predominant heparan sulfate proteoglycan in the developing and adult human brain. The two N-linked glycans and the C-terminal domain that attach the core protein to the cell membrane are not resolved in the Gpc1 crystal structure. Therefore, we have studied Gpc1 using crystallography, small angle x-ray scattering, and chromatographic approaches to elucidate the composition, structure, and function of the N-glycans and the C terminus and also the topology of Gpc1 with respect to the membrane. The C terminus is shown to be highly flexible in solution, but it orients the core protein transverse to the membrane, directing a surface evolutionarily conserved in Gpc1 orthologs toward the membrane, where it may interact with signaling molecules and/or membrane receptors on the cell surface, or even the enzymes involved in heparan sulfate substitution in the Golgi apparatus. Furthermore, the N-glycans are shown to extend the protein stability and lifetime by protection against proteolysis and aggregation.
Related Citations:
Improvements in the order, isotropy and electron density of glypican-1 crystals by controlled dehydration. Awad, W., Svensson Birkedal, G., Thunnissen, M.M., Mani, K., Logan, D.T. (2013) Acta Crystallogr D Biol Crystallogr 69: 2524
Crystal structure of N-glycosylated human glypican-1 core protein: structure of two loops evolutionarily conserved in vertebrate glypican-1. Svensson, G., Awad, W., Hakansson, M., Mani, K., Logan, D.T. (2012) J Biol Chem 287: 14040
Organizational Affiliation:
From the Department of Biochemistry and Structural Biology, Centre for Molecular Protein Science, Lund University, Box 124, SE-221 00 Lund, derek.logan@biochemistry.lu.se.
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