Prion protein "gamma-cleavage": characterizing a novel endoproteolytic processing event

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• The cellular prion protein (PrP(C)) has diverse functions, with known processing via alpha- and beta-cleavage.
• These known cleavage events produce distinct fragments (N1/C1, N2/C2) potentially serving different cellular roles.

Purpose of the Study:

• To identify and characterize novel cleavage events of the cellular prion protein (PrP(C)).
• To investigate the mechanism and cellular localization of this new cleavage event.

Main Methods:

• Engineered a C-terminal c-myc tag onto murine PrP(C) for fragment identification.
• Utilized a far-C-terminal anti-PrP antibody to detect and characterize novel fragments.
• Investigated cleavage timing within the secretory pathway and at the cell surface.

Main Results:

• Identified a new PrP(C) fragment, C3, resulting from 'gamma-cleavage'.
• Gamma-cleavage occurs during transit through the secretory pathway and on the cell surface, mediated by matrix metalloproteases.
• C3 is GPI-anchored but does not primarily localize to the cell surface and is preferentially cleaved from unglycosylated PrP(C).
• C3 is found in various cell types and brain tissue, with potential increases in human prion diseases.

Conclusions:

• A novel gamma-cleavage event of PrP(C) producing fragment C3 has been identified.
• This cleavage occurs in the secretory pathway and on the cell surface, potentially involving matrix metalloproteases.
• The presence of C3 in diverse tissues and its potential link to prion diseases highlight the significance of this underappreciated PrP(C) processing pathway.