Cholesterol signaling at the endoplasmic reticulum occurs in npc1(-/-) but not in npc1(-/-), LDLR(-/-) mice.
It remains controversial whether deficiency of the Niemann-Pick C1 (npc1) protein results in altered cholesterol signaling at the endoplasmic reticulum (ER). In this report, we have measured the processed, nuclear form of sterol regulatory element binding protein (SREBP)-1 in livers of npc1 wild-type, heterozygous, and homozygous deficient mice, alone, and in combination with deficiencies of the low density lipoprotein receptor (LDLR) or the multiple drug resistant (mdr)1a, P-glycoprotein. Cleavage of SREBPs to activated forms normally occurs when the ER is deficient in cholesterol. A large decrease in processed SREBP-1 was evident in fasted npc1(-/-) mice and npc1(-/-), mdr1a(-/-) mice, with no decrease evident in npc1(-/-), LDLR(-/-) mice. These results suggest that the increase in cellular cholesterol which occurs in npc1(-/-) and in npc1(-/-), mdr1a(-/-) mice includes the sites responsible for cholesterol signaling, while the similar increase in cholesterol found in npc1(-/-), LDLR(-/-) mice does not.
Erickson
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RP
Angel Charity for Children-Wings for Genetic Research, University of Arizona College of Medicine, Tucson, Arizona 85724, USA. erickson@peds.arizona.edu
Kiela
M
M
Garver
W S
WS
Krishnan
K
K
Heidenreich
R A
RA
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000172:deficiency / Q000235:genetics; D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005260:Female; D006579:Heterozygote; D006720:Homozygote; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D000077296:Niemann-Pick C1 Protein; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011973:Receptors, LDL / Q000172:deficiency* / Q000235:genetics; D012737:Sex Factors; D015398:Signal Transduction / Q000502:physiology; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors
D018435:ATP Binding Cassette Transporter, Subfamily B; D018528:ATP-Binding Cassette Transporters; D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D000077296:Niemann-Pick C1 Protein; C106831:Npc1 protein, mouse; D011506:Proteins; D011973:Receptors, LDL; C497388:Srebf1 protein, mouse; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; D002784:Cholesterol; C095122:multidrug resistance protein 3