Figure 9.

Schematic model for trafficking of HRP-P-selectin chimeras to SLMV in PC12 cells. HRP-P-selectin present on the plasma membrane is internalized into early Trn-positive, EGF-positive endosomes (EE) from which budding of SLMV occurs in a KCPL- and YGVF-dependent and BFA-sensitive manner. From the same endosomes, the remaining chimera is sorted to late, Trn-negative, EGF-positive endosomes (LE) in a KCPL-dependent, BFA-insensitive manner. From this compartment, further trafficking of P-selectin can occur in one of the two directions. One route leads to SLMV, a process that is controlled by YGVF and DPSP and is BFA sensitive. The remaining protein within LE is delivered to lysosomes (Lys) for degradation. Another potential SLMV precusor, represented by invaginations of the plasma membrane, from which budding of SLMV is BFA insensitive (12% for HRP-P-selectin vs. 88% that is BFA sensitive) and which does not involve an endosomal intermediate, is shown in the inset.