The subcellular localization of the Niemann-Pick Type C proteins depends on the adaptor complex AP-3.
Niemann-Pick Type C (NP-C) disease, caused by mutations in either human NPC1 (hNPC1) or human NPC2 (hNPC2), is characterized by the accumulation of unesterified cholesterol in late endosomes. Although it is known that the NP-C proteins are targeted to late endosomal/lysosomal compartments, their delivery mechanisms have not been fully elucidated. To identify mechanisms regulating NP-C protein localization, we used Saccharomyces cerevisiae, which expresses functional homologs of both NP-C proteins - scNcr1p and scNpc2p. Targeting of scNcr1p to the vacuole was perturbed in AP-3-deficient yeast cells, whereas the delivery of scNpc2p was affected by deficiencies in either AP-3 or GGA. We focused on the role of the AP-3 pathway in the targeting of the mammalian NP-C proteins. We found that, although mouse NPC1 (mNPC1) and hNPC2 co-localize with AP-3 to a similar extent in fibroblasts, hNPC2 preferentially co-localizes with AP-1. Importantly, the targeting of both mammalian NPC1 and NPC2 is dependent on AP-3. Moreover, and consistent with the NP-C proteins playing a role in cholesterol metabolism, AP-3-deficient cells have reduced levels of cholesterol. These results provide information about how the NP-C proteins are targeted to their sites of action and illustrate the possibility that defective sorting of the NP-C proteins along the endocytic route can alter cellular cholesterol.
Berger
Adam C
AC
Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA.
Salazar
Gloria
G
Styers
Melanie L
ML
Newell-Litwa
Karen A
KA
Werner
Erica
E
Maue
Robert A
RA
Corbett
Anita H
AH
Faundez
Victor
V
D033963:Adaptor Protein Complex 3 / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D000077296:Niemann-Pick C1 Protein; D009542:Niemann-Pick Diseases / Q000378:metabolism; D021381:Protein Transport; D011506:Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism; D033921:Vesicular Transport Proteins
D033963:Adaptor Protein Complex 3; D002352:Carrier Proteins; D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; C490168:NCR1 protein, S cerevisiae; C104585:NPC2 protein, human; D000077296:Niemann-Pick C1 Protein; C106831:Npc1 protein, mouse; C508484:Npc2 protein, S cerevisiae; D011506:Proteins; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D002784:Cholesterol