rs867186 — PROCR S219G

PROCR S219G — When Losing Your Anticoagulant Anchor Raises Clot Risk

The endothelial protein C receptor (EPCR, encoded by the PROCR gene on chromosome 20) is a transmembrane glycoprotein on vascular endothelial cells that serves as the essential docking station for protein C activation¹¹ protein C activation
protein C is a vitamin K-dependent anticoagulant zymogen; when bound to EPCR, it is activated 20-fold more efficiently by the thrombin-thrombomodulin complex on the endothelial surface. Once activated, protein C (as APC — activated protein C) inactivates clotting factors Va and VIIIa, shutting down thrombin generation and protecting vessels from inappropriate clot formation. EPCR also anchors APC for cytoprotective PAR1 signaling²² cytoprotective PAR1 signaling
protease-activated receptor 1 (PAR1) triggers anti-inflammatory and endothelial barrier-stabilizing responses when activated by APC bound to EPCR — a distinct pathway from the pro-thrombotic PAR1 activation triggered by thrombin.

The rs867186 (S219G) variant substitutes glycine for serine at position 219 in the extracellular ectodomain³³ ectodomain
the portion of a transmembrane protein exposed on the cell surface, which can be proteolytically cleaved and released into circulation as a soluble fragment of EPCR. This single amino acid change dramatically alters how tightly EPCR is held at the cell surface — with consequences for both coagulation and inflammation.

The Mechanism

The Ser→Gly substitution at position 219 sits within the stalk region of EPCR adjacent to the transmembrane domain, exactly where ADAM metalloprotease-10 (ADAM10) cleaves EPCR⁴⁴ ADAM metalloprotease-10 (ADAM10) cleaves EPCR
ADAM proteases are zinc-dependent enzymes that shed ectodomains of membrane proteins; the 219Gly variant loosens the local protein structure, making the cleavage site more accessible to release soluble EPCR (sEPCR) into the bloodstream.

GG homozygotes have four-fold higher circulating sEPCR levels compared to AA homozygotes⁵⁵ GG homozygotes have four-fold higher circulating sEPCR levels compared to AA homozygotes
Ireland et al. Atherosclerosis 2005 — in vitro transfection confirmed increased basal release from cells expressing 219Gly. This has two opposing effects:

Pro-thrombotic pathway: sEPCR competitively sequesters circulating protein C away from the surface-bound EPCR that would activate it. Despite higher plasma protein C levels (because less is being activated and consumed), the functional anticoagulant response is blunted — protein C circulates but cannot dock efficiently on endothelial cells to be activated. Simultaneously, FVII and downstream coagulation activation markers (FIXpep, FXpep, prothrombin F1+2) rise proportionally with Gly allele dose⁶⁶ Gly allele dose
FVII elevated 6.9% in AG carriers and 23.4% in GG carriers vs AA, with a co-proportional rise in activated coagulation markers; Ireland et al. ATVB 2009, indicating net procoagulant shift despite the elevated protein C.

Anti-inflammatory pathway: sEPCR and APC-sEPCR complexes attenuate leukocyte-endothelial adhesion and vascular inflammation — explaining the paradoxical lower coronary artery disease risk in G allele carriers⁷⁷ paradoxical lower coronary artery disease risk in G allele carriers
Stacey et al., Nature Communications 2022 — PROCR-219Gly simultaneously reduces CAD risk through anti-inflammatory EPCR signaling while raising VTE risk through the coagulation FVII arm. This cross-phenotype pleiotropy — where the same variant decreases one vascular endpoint while increasing another — illustrates why simple "pro-thrombotic" labels can be misleading.

The Evidence

The VTE risk from rs867186 is among the most replicated associations in venous thrombosis genetics.

A HuGE meta-analysis of 37,415 cases and 84,406 non-cases across 25 studies⁸⁸ HuGE meta-analysis of 37,415 cases and 84,406 non-cases across 25 studies
Dennis et al. Blood 2012 — random-effects model, additive genetic model found each additional G allele increases VTE odds by 22% (OR 1.22, 95% CI 1.11–1.33, P < 0.001). No association was found with arterial MI.

A prospective Swedish cohort of 28,794 subjects followed through 2018⁹⁹ prospective Swedish cohort of 28,794 subjects followed through 2018
Manderstedt et al. Thrombosis and Haemostasis 2022 — Malmö Diet and Cancer Study, exome sequencing found only GG homozygosity — not AG heterozygosity — reached significance, with an adjusted HR of 1.5 (95% CI 1.1–2.0). This recessive-at-the-clinical-threshold pattern aligns with the dose-response in coagulation markers.

A subsequent meta-analysis of 5,768 cases and 30,017 controls¹⁰¹⁰ meta-analysis of 5,768 cases and 30,017 controls
Pituk et al. Front Cardiovasc Med 2023 — pooled analysis including their own Hungarian case-control study quantified genotype-specific risk more precisely: dominant model OR 1.27 (95% CI 1.11–1.46), recessive model OR 1.60 (95% CI 1.26–2.04), and GG versus AA OR 1.64 (95% CI 1.28–2.09). The same study found a non-significant trend toward higher VTE recurrence risk (OR 1.72, 95% CI 0.95–3.13, p = 0.075) in G carriers — a signal that may be meaningful for anticoagulation duration decisions.

At the genome-wide level, Thibord et al. Circulation 2022¹¹¹¹ Thibord et al. Circulation 2022
cross-ancestry GWAS of up to 81,669 VTE cases from 30 studies in European, African, and Hispanic populations — confirmed PROCR as an independent VTE locus among 135 significant signals and the Ghouse et al. Nature Genetics 2023¹²¹² Ghouse et al. Nature Genetics 2023
genome-wide meta-analysis of 81,190 cases and 1,419,671 controls — 93 risk loci, with PROCR among replication-confirmed signals both confirmed PROCR as an independent VTE risk locus in the largest genetic studies of venous thromboembolism conducted to date.

Practical Actions

For AG heterozygotes (the most common risk genotype at ~17.5% prevalence), the absolute risk increase is modest and typically does not alter standard clinical management. The key implication is awareness: recognizing an elevated baseline risk enables informed decisions around high-risk exposures such as prolonged immobility, surgery, or estrogen-containing contraceptives.

For GG homozygotes (~1% prevalence), the risk increment is clinically more meaningful (HR ~1.5 for incident VTE, OR ~1.64 in meta-analysis). This genotype warrants factoring into thrombotic risk stratification, particularly after a first unprovoked VTE when deciding on anticoagulation duration. PROCR S219G does not carry standalone indication for prophylactic anticoagulation, but it strengthens the case for extended therapy in ambiguous clinical scenarios.

The anti-inflammatory pleiotropic effect (lower CAD risk) does not require intervention — it is a passive benefit of the shedding mechanism.

Interactions

Factor V Leiden (rs6025) and prothrombin G20210A (rs1799963) are the strongest known inherited thrombophilia variants. Combining rs867186 with either of these creates a substantially higher cumulative VTE risk than any single variant alone, as these operate through independent mechanisms — FVII/PROCR pathway versus thrombin generation and fibrin deposition. Any carrier of rs867186 GG who also carries factor V Leiden or prothrombin mutation should be evaluated by a hematologist for thrombophilia risk stratification.

A second functional PROCR variant, Arg113Cys (rs146420040), was identified in the same Malmö cohort study and confers independent VTE risk (HR 1.3). The combination of both PROCR variants in the same individual has not been formally studied but would be expected to compound risk further.