rs12487736 — SCAP SCAP Val798Ile

Missense variant in the SCAP cholesterol-sensor gene (Val798Ile)

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SCAP Val798Ile — The Cholesterol-Sensor Variant at the Heart of Plaque Formation

Before a cell can respond to low cholesterol by making more, it needs to sense the deficit. That sensing job belongs to SCAP (SREBP cleavage-activating protein)11 SCAP (SREBP cleavage-activating protein)
a seven-transmembrane sterol-sensing protein in the ER membrane that escorts SREBP transcription factors to the Golgi for proteolytic activation. When cholesterol is plentiful, SCAP is detained at the ER by INSIG proteins. When cholesterol drops, SCAP escorts SREBP-2 to the Golgi, where it is cleaved and activated — driving LDL receptor and HMG-CoA reductase expression to restore cholesterol supply. The rs12487736 variant changes valine to isoleucine at position 798 of SCAP, sitting within the WD-repeat domain that contacts SREBP-2.

The Mechanism

The SCAP Val798Ile substitution lies in the carboxy-terminal WD40 repeat region of SCAP, which mediates direct protein-protein contact with SREBP-2's regulatory domain. In genome-wide expression profiling of 20 human atherosclerotic plaque samples (carotid, aortic, femoral) versus 6 control vessel samples22 genome-wide expression profiling of 20 human atherosclerotic plaque samples (carotid, aortic, femoral) versus 6 control vessel samples
Fan et al., Thrombosis Journal, 2008, SREBF-2 mRNA was significantly downregulated in carotid plaques (p=0.02), suggesting that reduced SREBF-2 transcriptional activity in inflamed vascular tissue is a feature of established atherosclerosis rather than a compensatory response.

Under inflammatory conditions, the mTOR pathway activates the SCAP–SREBP-2 complex, increasing its translocation from the ER to the Golgi and driving excess LDL receptor expression and cholesterol uptake into vascular cells. SCAP knockdown in smooth muscle cells of ApoE-/- mice33 SCAP knockdown in smooth muscle cells of ApoE-/- mice
Li et al., FASEB J, 2019 significantly reduced atherosclerotic plaque burden, confirming SCAP as a causal driver of lesion formation rather than merely a correlate.

The Evidence

The most compelling cardiovascular evidence comes from an autopsy-based study in 300 middle-aged Finnish men who died suddenly without prior diagnosed heart disease44 autopsy-based study in 300 middle-aged Finnish men who died suddenly without prior diagnosed heart disease
Fan et al., Thromb J, 2008. Researchers genotyped SCAP 2386A>G (rs12487736) and SREBF2 1784G>C (rs2228314) and correlated genotypes with coronary artery narrowing and lesion characteristics. On its own, the SCAP G allele (plus-strand C at rs12487736) did not reach independent significance for SCD risk. However, men carrying both the SCAP G allele and the SREBF2 C allele had a 2.68-fold elevated risk of sudden cardiac death (OR 2.68, 95% CI 1.07–6.71; interaction p=0.046), pointing to a gene-gene amplification effect when both components of the SCAP–SREBP-2 circuit carry functional variants simultaneously.

In pediatric cohorts, the variant also influences metabolic phenotypes: in 2,021 Chinese schoolchildren55 2,021 Chinese schoolchildren
Yang et al., PLoS One, 2017, rs12487736 was associated with both systolic BP (β=1.66, p=0.003) and diastolic BP (β=1.35, p=0.024), with a 36% elevated odds of high blood pressure in overweight/obese children (OR 1.36, 95% CI 1.02–1.82).

A study of 614 HIV-positive individuals on antiretroviral therapy66 study of 614 HIV-positive individuals on antiretroviral therapy
Lazzaretti et al., ScientificWorldJournal, 2013 also found the variant associated with HDL-cholesterol levels, consistent with SCAP's broad role in sterol balance across lipoprotein fractions.

Practical Actions

For CC homozygotes, the most actionable implication is the additive risk when combined with the SREBF2 C allele (rs2228314). Checking both variants together informs a meaningful risk stratification that neither variant achieves alone.

Interactions

The critical interaction is with SREBF2 rs2228314 (Gly595Ala). SCAP is the direct chaperone and sterol sensor for SREBP-2.

Genotype Interpretations

What each possible genotype means for this variant.

TT Normal

Standard SCAP cholesterol-sensor function

You carry two copies of the T allele (coding-strand A) at SCAP rs12487736, the common protective genotype. In European populations, approximately 33% of individuals share this genotype. No elevated cardiovascular risk from this variant is expected based on current evidence.

CT Intermediate

One copy of the SCAP C allele — modest risk contribution to the cholesterol-sensing pathway

Most association studies for this variant have used dominant or additive models rather than isolating heterozygous effects. For heterozygotes, the key clinical relevance is the gene-gene interaction within the SCAP-SREBP-2 pathway — the 2.68-fold SCD risk requires functional variants at both loci.

CC High Risk

Homozygous SCAP C allele — elevated risk via impaired cholesterol-sensing feedback, especially in combination with SREBF2 variant

The SCAP protein's WD-repeat C-terminal domain physically contacts the regulatory domain of SREBP-2, facilitating ER-to-Golgi transport and proteolytic cleavage when cellular cholesterol is low. The Val798Ile change sits in this interaction region. While the variant's independent effect on SCD risk did not reach significance in the 300-sample Finnish autopsy study (likely insufficient power for single-variant analysis), the gene-gene interaction result (p=0.046 for the SCAP G × SREBF2 C combination) indicates that functional impairment at both ends of the sensing relay amplifies cardiovascular risk beyond what either variant contributes alone.