Akt activation increases cellular cholesterol by promoting the proteasomal degradation of Niemann-Pick C1.
Null mutations of the Niemann-Pick type C1 (NPC1) gene cause NPC disease, a lysosomal storage disorder characterized by cholesterol accumulation in late endosomes (LE) and lysosomes (Ly). Nascent or mutated NPC1 is degraded through the ubiquitin-proteasome pathway, but how NPC1 degradation is regulated remains currently unknown. In the present study, we demonstrated a link between NPC1 degradation and the Akt (protein kinase B)/mTOR [mammalian (or mechanistic) target of rapamycin] signalling pathway in cervical cancer cell lines. We provided evidence that activated Akt/mTOR pathway increased NPC1 degradation by ∼50% in C33A cells when compared with SiHa or HeLa cells. NPC1 degradation in C33A cells was reversed when Akt/mTOR activation was blocked by specific inhibitors or when mTORC1 (mTOR complex 1) was disrupted by regulatory associated protein of mTOR (Raptor) knockdown. Importantly, inhibition of the Akt/mTOR pathway led to decreased NPC1 ubiquitination in C33A cells, pointing to a role of Akt/mTOR in the proteasomal degradation of NPC1. Moreover, we found that NPC1 depletion in several cancer cell lines inhibited cell proliferation and migration. Our results uncover Akt as a key regulator of NPC1 degradation and link NPC1 to cancer cell proliferation and migration.
School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, NSW 2052, Australia x.r.du@unsw.edu.au h.rob.yang@unsw.edu.au.
Ximing
X
Du
School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, NSW 2052, Australia.
Yuxi
Y
Zhang
School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, NSW 2052, Australia.
Sae Rom
SR
Jo
School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, NSW 2052, Australia.
Xiaoyun
X
Liu
School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, NSW 2052, Australia.
Yanfei
Y
Qi
School of Medical Sciences, the University of New South Wales, Sydney, NSW 2052, Australia Diabetes & Obesity Research Program, Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia.
Brenna
B
Osborne
School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, NSW 2052, Australia.
Frances L
FL
Byrne
School of Medical Sciences, the University of New South Wales, Sydney, NSW 2052, Australia.
Greg C
GC
Smith
School of Medical Sciences, the University of New South Wales, Sydney, NSW 2052, Australia.
Nigel
N
Turner
School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, NSW 2052, Australia.
Kyle L
KL
Hoehn
School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, NSW 2052, Australia.
Andrew J
AJ
Brown
School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, NSW 2052, Australia x.r.du@unsw.edu.au h.rob.yang@unsw.edu.au.
Hongyuan
H
Yang
D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation / Q000235:genetics; D002784:Cholesterol / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D000076222:Mechanistic Target of Rapamycin Complex 1; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000077296:Niemann-Pick C1 Protein; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D059748:Proteolysis; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D046912:Multiprotein Complexes; C106881:NPC1 protein, human; D000077296:Niemann-Pick C1 Protein; D002784:Cholesterol; C546842:MTOR protein, human; D000076222:Mechanistic Target of Rapamycin Complex 1; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D046988:Proteasome Endopeptidase Complex
C-terminus of Hsc70-interacting protein (CHIP); Niemann–Pick type C1 (NPC1); cancer; cholesterol; mechanistic target of rapamycin (mTOR); ubiquitination