Table 3. Three separate mechanisms act concurrently to shed and release PrP^C from the PrP-expressing cell culture system used in this study.

Mechanism of release	PrP fragment	Time course of released PrPwt	Time course of released PrPΔ121–123	Suggested compartment	Proposed enzymatic activity	Inhibition or hindering
α-cleavage	N1 (11 kDa)	20 min	20 min (rate inhibited by 45%)	Cell membrane	Putative α-PrPase	Deletions in the site for α-cleavage
Extreme C-terminal cleavage	FL-S C1-S	40–60 min	40–60 min	Endocytic compartment	Metallo-protease(s)	O-phenanthroline, TAPI-1
Exosomal release	FL C1	5–6 h	5–6 h	MVBs	N/A	-

N/A, not applicable.