Jk. Burkhardt et al., THE GIANT ORGANELLES IN BEIGE AND CHEDIAK-HIGASHI FIBROBLASTS ARE DERIVED FROM LATE ENDOSOMES AND MATURE LYSOSOMES, The Journal of experimental medicine, 178(6), 1993, pp. 1845-1856
Chediak-Higashi Syndrome (CHS) is an autosomal recessive disease affec
ting secretory granules and lysosome-like organelles. In CHS fibroblas
ts, acidic organelles are abnormally large and clustered in the perinu
clear area. We have analyzed fibroblast cell lines from a CHS patient
and from the murine model for CHS, the beige mouse, to determine which
lysosome-like compartments are affected. Uptake of neutral red showed
that in both beige and CHS cell lines, the acidic organelles were mar
kedly clustered in the perinuclear region of the cells. Giant organell
es (>4 mum) were observed in a fraction of the cells, and these were m
ore dramatic in the beige fibroblasts than in the CHS fibroblasts. The
total dye uptake of both mutant cell lines was similar to their respe
ctive wild type fibroblasts, suggesting that the overall volume of aci
dic compartments is unaffected by the disorder. Histochemistry and imm
unofluorescence showed that the giant organelles in both beige and CHS
fibroblasts were positive for cathepsin D, lysosome-associated membra
ne protein (LAMP) 1, LAMP 2, and a 120-kD lysosomal glycoprotein, all
marker proteins for late endosomes and lysosomes. The giant organelles
were also negative for transferrin receptor and mannose-6-phosphate r
eceptor, and most of them were also negative for rab 7. This distribut
ion of marker proteins shows that the giant organelles in both beige a
nd CHS are derived from late compartments of the endocytic pathway. Th
is conclusion was confirmed using endocytic tracers. BSA was transport
ed to the giant organelles, but only after long incubation times, and
only at 37-degrees-C. Alpha2-macroglobulin was taken up and degraded a
t similar rates by CHS or beige cells and their respective wild type c
ontrol cells. Taken together, our results indicate that the mutation i
n CHS specifically affects late endosomes and lysosomes, with little o
r no effect on early endosomes. Although the mutation clearly causes m
islocalization of these organelles, it appears to have little effect o
n their endocytic and degradative functions.