Apolipoprotein H (APOH)

Apolipoprotein H (APOH), also known as Beta-2-glycoprotein 1, Activated protein C-binding protein, B2GPI, and B2G1, is a glycoprotein synthesized by liver cells and it is present in the blood associated with plasma lipoproteins. It is an essential cofactor for the binding of certain antiphospholipid antibodies (APA) to anionic phospholipid. APOH binds to various kinds of negatively charged substances such as heparin, phospholipids, and dextran sulfate. APOH may prevent activation of the intrinsic blood coagulation cascade by binding to phospholipids on the surface of damaged cells. APOH appears to completely inhibit serotonin release by the platelets and prevents subsequent waves of the ADP-induced aggregation. The activity of APOH appears to involve the binding of agglutenating, negatively charged compounds, and inhibits agglutenation by the contact activation of the intrinsic blood coagulation pathway. APOH causes a reduction of the prothrombinase binding sites on platelets and reduces the activation caused by collagen when thrombin is present at physiological serum concentrations of APOH suggesting a regulatory role of APOH in coagulation. APOH plasma concentrations are strongly associated to metabolic syndrome alterations and vascular disease in type 2 diabetic and could be considered as a clinical marker of cardiovascular risk. APOH is found on several classes of lipoproteins, and is involved in the activation of lipoprotein lipase in lipid metabolism. This single-chain glycoprotein also has been implicated in several physiologic pathways including coagulation and the production of hypertension, which are related to the pathogenesis of primary cerebral hemorrhage (PICH).

Apolipoprotein H (APOH) Related Areas

Immunology>>Innate Immunity>>Coagulation>>Apolipoprotein H/APOH

Cardiovascular>>Coagulation>>Apolipoprotein H/APOH

Cardiovascular>>Lipid Metabolism>>Apolipoprotein H/APOH

Apolipoprotein H (APOH) Alternative Names

Apolipoprotein H, APOH, B2G1, BG [Homo sapiens]

Apolipoprotein H, Apoh, B2GPI, RP23-261J24.1, beta-2-GPI, beta2-GPI [Mus musculus]

Summaries for Apolipoprotein H (APOH)

Entrez Gene summary for Apolipoprotein H (APOH):

Apolipoprotein H has been implicated in a variety of physiologic pathways including lipoprotein metabolism, coagulation, and the production of antiphospholipid autoantibodies. APOH may be a required cofactor for anionic phospholipid binding by the antiphospholipid autoantibodies found in sera of many patients with lupus and primary antiphospholipid syndrome, but it does not seem to be required for the reactivity of antiphospholipid autoantibodies associated with infections

OMIM - description for Apolipoprotein H (APOH):

The APOH gene encodes beta-2 glycoprotein I, also known as apolipoprotein H, a single-chain plasma protein of about 50 kD. Beta-2 GPI binds to and neutralizes negatively charged phospholipid macromolecules, thereby diminishing inappropriate activation of the intrinsic blood coagulation cascade. Beta-2 GPI has been implicated in a variety of physiologic pathways, including blood coagulation, hemostasis, and the production of antiphospholipid antibodies characteristic of antiphospholipid syndrome

Wikipedia summary for Apolipoprotein H (APOH):

Apolipoprotein H (Apo-H), previously known as (β2-glycoprotein I, beta-2 glycoprotein I), is a multifunctional apolipoprotein. One of its functions is to bind cardiolipin. When bound the structure of cardiolipin and Apo-H both undergo large changes in structure.[1] Within the structure of Apo-H is a stretch of positively charged amino acids, (protein sequence positions 282-287) Lys-Asn-Lys-Glu-Lys-Lys, are involved in phospholipid binding (See image on right).[2] Apo-H has a complex involvement in agglutination, it appears to alter ADP mediated agglutenation of platlets.[3] Normally Apo-H assumes an anti-coagulation activity in serum (by inhibiting coagulation factors), however changes in blood factors can result of a reversal of that activity.

Human Apolipoprotein H (APOH) Protein General Information

 

• Protein names: Recommended name: Beta-2-glycoprotein 1 Short name=B2GPI Short name=Beta(2)GPI
• Sequence length: 345 AA.
• Domain: Repeat Signal Sushi
• Sequence similarities: Contains 4 Sushi (CCP/SCR) domains.
• Post-translational modification: N- and O-glycosylated. Ref.10 also reports glycosylation on 'Asn-188' for their allele.
• Subcellular location: Secreted.
• Tissue specificity: Expressed by the liver and secreted in plasma.

General information above from UniProt

Function for Apolipoprotein H (APOH) Protein

UniProtKB:

Binds to various kinds of negatively charged substances such as heparin, phospholipids, and dextran sulfate. May prevent activation of the intrinsic blood coagulation cascade by binding to phospholipids on the surface of damaged cells.

Genatlas:

• Apolipoprotein H (APOH) is precursor activator of lipoprotein lipase
• Apolipoprotein H (APOH) is cofactor for the binding of antianionic phospholipid autoantibodies
• Apolipoprotein H (APOH) may prevent activation of the intrinsic blood coagulation cascade by binding to phospholipids on the surface of damaged cells
• Apolipoprotein H (APOH) acts as a lipid transporter

Homology for human Apolipoprotein H (APOH)

• ortholog to murine Apoh
• ortholog to Canis familiari APOH

Drugs for Apolipoprotein H (APOH)

Target	Drug Name	Disease	Drug Status
Apolipoprotein H (APOH)	LJP-1082	Antiphospholipid syndrome	Phase I

Drugs for Apolipoprotein H (APOH) from TTD (Therapeutic Targets Database)