Sterol-regulatory element-binding protein (SREBP)-2 contributes to polygenic hypercholesterolaemia.
Sterol-regulatory element-binding protein (SREBP)-2 is a key regulator of cholesterol. When cells are deprived of cholesterol, proteolytic cleavage releases the NH(2)-terminal domain of SREBP-2 that binds and activates the promoters of SREBP-2-regulated genes including the genes encoding the low-density lipoprotein (LDL) receptor, 3-hydroxymethyl-3-glutaryl-(HMG-)CoA-synthase, and HMG-CoA-reductase. Thus, SREPB-2 gene activation leads to enhanced cholesterol uptake and biosynthesis. A novel protein polymorphism (SREBP-2-595A/G) discovered in the regulatory domain of human SREBP-2 was investigated regarding its impact on cholesterol homeostasis. In human embryonic kidney (HEK)-293-cells, the cleavage-rate of the SREBP-2-595A-isoform was slightly decreased compared to that of the SREBP-2-595G-isoform. Since cleavage of SREBP-2 activates the LDL receptor-mediated uptake of plasma cholesterol, we hypothesized the LDL receptor-mediated uptake to be decreased in homozygous SREBP-2-595A-carriers and thus, plasma total cholesterol (TC) to be higher than in SREBP-2-595G-carriers. Multiple linear regression analysis of population samples from Switzerland (N=1334) and Israel (N=923) demonstrated a significant positive, gene dose-dependent association of the SREBP-2-595A-isoform with higher plasma TC (P=0.001). This cholesterol-modulating effect was present in hypercholesterolaemic (DeltaTC=1.05 mmol/l, 14.4%; P=0.002; N=477), but absent in normocholesterolaemic subjects (DeltaTC=0.06 mmol/l, 1.4%; P=0.334; N=1780). In summary, a slightly but constantly decreased cleavage-rate of the SREBP-2-595A-isoform compared to that of the SREBP-2-595G-isoform may lead to a reduced transcriptional activation of the LDL receptor-gene weakening the SREBP-mediated compensation mechanisms, and may, therefore, be a critical factor in the development of polygenic hypercholesterolaemia.
Miserez
André R
AR
Cardiovascular Genetics, Institute of Biochemistry and Genetics, Department of Clinical-Biological Sciences, University of Basel, Vesalgasse 1, Ch-4051, Basel, Switzerland. andre-r.miserez@unibas.ch
Muller
Patrick Y
PY
Barella
Luca
L
Barella
Sandra
S
Staehelin
Hannes B
HB
Leitersdorf
Eran
E
Kark
Jeremy D
JD
Friedlander
Yechiel
Y
D000293:Adolescent; D000328:Adult; D015153:Blotting, Western; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D005838:Genotype; D006801:Humans; D006937:Hypercholesterolemia / Q000235:genetics* / Q000378:metabolism; D008297:Male; D020641:Polymorphism, Single Nucleotide; D015995:Prevalence; D020033:Protein Isoforms; D017433:Protein Structure, Secondary; D051782:Sterol Regulatory Element Binding Protein 2; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D020033:Protein Isoforms; C497390:SREBF2 protein, human; D051782:Sterol Regulatory Element Binding Protein 2; D014157:Transcription Factors