The Niemann-Pick C1 protein resides in a vesicular compartment linked to retrograde transport of multiple lysosomal cargo.
Niemann-Pick C disease (NP-C) is a neurovisceral lysosomal storage disorder. A variety of studies have highlighted defective sterol trafficking from lysosomes in NP-C cells. However, the heterogeneous nature of additional accumulating metabolites suggests that the cellular lesion may involve a more generalized block in retrograde lysosomal trafficking. Immunocytochemical studies in fibroblasts reveal that the NPC1 gene product resides in a novel set of lysosome-associated membrane protein-2 (LAMP2)(+)/mannose 6-phosphate receptor(-) vesicles that can be distinguished from cholesterol-enriched LAMP2(+) lysosomes. Drugs that block sterol transport out of lysosomes also redistribute NPC1 to cholesterol-laden lysosomes. Sterol relocation from lysosomes in cultured human fibroblasts can be blocked at 21 degrees C, consistent with vesicle-mediated transfer. These findings suggest that NPC1(+) vesicles may transiently interact with lysosomes to facilitate sterol relocation. Independent of defective sterol trafficking, NP-C fibroblasts are also deficient in vesicle-mediated clearance of endocytosed [14C]sucrose. Compartmental modeling of the observed [14C]sucrose clearance data targets the trafficking defect caused by mutations in NPC1 to an endocytic compartment proximal to lysosomes. Low density lipoprotein uptake by normal cells retards retrograde transport of [14C]sucrose through this same kinetic compartment, further suggesting that it may contain the sterol-sensing NPC1 protein. We conclude that a distinctive organelle containing NPC1 mediates retrograde lysosomal transport of endocytosed cargo that is not restricted to sterol.
Neufeld
E B
EB
Lipid Cell Biology Section, Laboratory of Cell Biochemistry and Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA.
Wastney
M
M
Patel
S
S
Suresh
S
S
Cooney
A M
AM
Dwyer
N K
NK
Roff
C F
CF
Ohno
K
K
Morris
J A
JA
Carstea
E D
ED
Incardona
J P
JP
Strauss
J F
JF
Vanier
M T
MT
Patterson
M C
MC
Brady
R O
RO
Pentchev
P G
PG
Blanchette-Mackie
E J
EJ
D000595:Amino Acid Sequence; D000906:Antibodies; D015703:Antigens, CD / Q000378:metabolism; D001692:Biological Transport; D002352:Carrier Proteins; D002451:Cell Compartmentation; D002784:Cholesterol / Q000378:metabolism; D004705:Endocytosis; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D052119:Lysosomal-Associated Membrane Protein 2; D051907:Lysosomal Membrane Proteins; D008247:Lysosomes / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D000077296:Niemann-Pick C1 Protein; D009542:Niemann-Pick Diseases / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D013329:Structure-Activity Relationship; D013395:Sucrose / Q000378:metabolism
D000906:Antibodies; D015703:Antigens, CD; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C497811:LAMP2 protein, human; D052119:Lysosomal-Associated Membrane Protein 2; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins; C106881:NPC1 protein, human; D000077296:Niemann-Pick C1 Protein; D011506:Proteins; D017527:Receptor, IGF Type 2; D013395:Sucrose; D002784:Cholesterol