Cell-surface prion protein interacts with glycosaminoglycans

Area of Science:

• Biochemistry
• Cell Biology
• Neuroscience

Background:

• Prion protein (PrP) is implicated in neurodegenerative diseases.
• The interaction of PrP with glycosaminoglycans (GAGs) is poorly understood.
• GAGs are crucial components of the extracellular matrix and cell surfaces.

Purpose of the Study:

• To investigate the binding characteristics of PrP to various GAGs.
• To identify the region of PrP involved in GAG binding.
• To determine the role of divalent cations in PrP-GAG interactions.
• To explore the function of PrP as a cell surface receptor for GAGs.

Main Methods:

• Enzyme-linked immunosorbent assay (ELISA)
• Flow cytometry
• Use of recombinant human PrP (rPrP) and full-length native PrPC
• Synthetic peptide mapping
• Cell surface binding assays

Main Results:

• Recombinant PrP (rPrP) binds to multiple GAGs, including chondroitin sulphate A, chondroitin sulphate B, hyaluronic acid, and heparin.
• Binding occurs via the N-terminus of PrP and is significantly enhanced by Cu2+ and Zn2+ ions.
• Heparin exhibits the strongest binding affinity for PrP, with inhibition observed using specific heparin analogues.
• Full-length PrPC from human brain and wild-type PrPC on cell surfaces bind GAGs, particularly heparin, in a manner dependent on the N-terminus.
• Cell-surface heparin binding leads to a reduction in cell-surface PrPC levels.

Conclusions:

• Prion protein (PrP) directly binds to glycosaminoglycans (GAGs) through its N-terminal region.
• Divalent cations, specifically Cu2+ and Zn2+, modulate PrP-GAG interactions.
• Cellular prion protein (PrPC) functions as a cell surface receptor for GAGs, influencing its own cell surface levels.