1. HSPGs are present in basement membranes
(perlecan, agrin, and collagen XVIII), where
they collaborate with other matrix components
to define basement membrane structure
and to provide a matrix for cell migration.
2. HSPGs are found in secretory vesicles, most
notably serglycin, which plays a role in
packaging granular contents, maintaining
proteases in an active state, and regulating
various biological activities after secretion