1u0n

Structural highlights

Disease

[GP1BA_HUMAN] Genetic variations in GP1BA may be a cause of susceptibility to non-arteritic anterior ischemic optic neuropathy (NAION) [MIM:258660]. NAION is an ocular disease due to ischemic injury to the optic nerve. It usually affects the optic disk and leads to visual loss and optic disk swelling of a pallid nature. Visual loss is usually sudden, or over a few days at most and is usually permanent, with some recovery possibly occurring within the first weeks or months. Patients with small disks having smaller or non-existent cups have an anatomical predisposition for non-arteritic anterior ischemic optic neuropathy. As an ischemic episode evolves, the swelling compromises circulation, with a spiral of ischemia resulting in further neuronal damage.^[1] Defects in GP1BA are a cause of Bernard-Soulier syndrome (BSS) [MIM:231200]; also known as giant platelet disease (GPD). BSS patients have unusually large platelets and have a clinical bleeding tendency.^{[2] [3] [4] [5] [6] [7]} Defects in GP1BA are the cause of benign mediterranean macrothrombocytopenia (BMM) [MIM:153670]; also known as autosomal dominant benign Bernard-Soulier syndrome. BMM is characterized by mild or no clinical symptoms, normal platelet function, and normal megakaryocyte count.^[8] Defects in GP1BA are the cause of pseudo-von Willebrand disease (VWDP) [MIM:177820]. A bleeding disorder is caused by an increased affinity of GP-Ib for soluble vWF resulting in impaired hemostatic function due to the removal of vWF from the circulation.^{[9] [10] [11] [12]} [VWF_HUMAN] Defects in VWF are the cause of von Willebrand disease type 1 (VWD1) [MIM:193400]. A common hemorrhagic disorder due to defects in von Willebrand factor protein and resulting in impaired platelet aggregation. Von Willebrand disease type 1 is characterized by partial quantitative deficiency of circulating von Willebrand factor, that is otherwise structurally and functionally normal. Clinical manifestations are mucocutaneous bleeding, such as epistaxis and menorrhagia, and prolonged bleeding after surgery or trauma.^{[13] [14]} Defects in VWF are the cause of von Willebrand disease type 2 (VWD2) [MIM:613554]. A hemorrhagic disorder due to defects in von Willebrand factor protein and resulting in impaired platelet aggregation. Von Willebrand disease type 2 is characterized by qualitative deficiency and functional anomalies of von Willebrand factor. It is divided in different subtypes including 2A, 2B, 2M and 2N (Normandy variant). The mutant VWF protein in types 2A, 2B and 2M are defective in their platelet-dependent function, whereas the mutant protein in type 2N is defective in its ability to bind factor VIII. Clinical manifestations are mucocutaneous bleeding, such as epistaxis and menorrhagia, and prolonged bleeding after surgery or trauma. Defects in VWF are the cause of von Willebrand disease type 3 (VWD3) [MIM:277480]. A severe hemorrhagic disorder due to a total or near total absence of von Willebrand factor in the plasma and cellular compartments, also leading to a profound deficiency of plasmatic factor VIII. Bleeding usually starts in infancy and can include epistaxis, recurrent mucocutaneous bleeding, excessive bleeding after minor trauma, and hemarthroses.

Function

[GP1BA_HUMAN] GP-Ib, a surface membrane protein of platelets, participates in the formation of platelet plugs by binding to the A1 domain of vWF, which is already bound to the subendothelium. [VWF_HUMAN] Important in the maintenance of hemostasis, it promotes adhesion of platelets to the sites of vascular injury by forming a molecular bridge between sub-endothelial collagen matrix and platelet-surface receptor complex GPIb-IX-V. Also acts as a chaperone for coagulation factor VIII, delivering it to the site of injury, stabilizing its heterodimeric structure and protecting it from premature clearance from plasma. [LECBB_BOTJA] Snaclec that activates platelets by targeting vWF/GPIb. Two-chain botrocetin forms an activated complex with vWF (by binding the A1 domain), and the complex then binds to platelet glycoprotein Ibalpha (GP1BA), resulting in platelet aggregation. There are two distinct forms of the von Willebrand factor-dependent platelet coagglutinin. The dimeric form is 34-times more active than the one-chain botrocetin in promoting vWF binding to platelets. [LECBA_BOTJA] Snaclec that activates platelets by targeting vWF/GPIb. Two-chain botrocetin forms an activated complex with vWF (by binding the A1 domain), and the complex then binds to platelet glycoprotein Ibalpha (GP1BA), resulting in platelet aggregation. There are two distinct forms of the von Willebrand factor-dependent platelet coagglutinin. The dimeric form is 34-times more active than the one-chain botrocetin in promoting vWF binding to platelets.

Evolutionary Conservation

Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.

See Also

• Platelet-receptor glycoprotein Ib alpha

References

1. ↑ Salomon O, Rosenberg N, Steinberg DM, Huna-Baron R, Moisseiev J, Dardik R, Goldan O, Kurtz S, Ifrah A, Seligsohn U. Nonarteritic anterior ischemic optic neuropathy is associated with a specific platelet polymorphism located on the glycoprotein Ibalpha gene. Ophthalmology. 2004 Jan;111(1):184-8. PMID:14711733 doi:10.1016/j.ophtha.2003.05.006
2. ↑ Miller JL, Lyle VA, Cunningham D. Mutation of leucine-57 to phenylalanine in a platelet glycoprotein Ib alpha leucine tandem repeat occurring in patients with an autosomal dominant variant of Bernard-Soulier disease. Blood. 1992 Jan 15;79(2):439-46. PMID:1730088
3. ↑ Ware J, Russell SR, Marchese P, Murata M, Mazzucato M, De Marco L, Ruggeri ZM. Point mutation in a leucine-rich repeat of platelet glycoprotein Ib alpha resulting in the Bernard-Soulier syndrome. J Clin Invest. 1993 Sep;92(3):1213-20. PMID:7690774 doi:http://dx.doi.org/10.1172/JCI116692
4. ↑ Simsek S, Noris P, Lozano M, Pico M, von dem Borne AE, Ribera A, Gallardo D. Cys209 Ser mutation in the platelet membrane glycoprotein Ib alpha gene is associated with Bernard-Soulier syndrome. Br J Haematol. 1994 Dec;88(4):839-44. PMID:7819107
5. ↑ de la Salle C, Baas MJ, Lanza F, Schwartz A, Hanau D, Chevalier J, Gachet C, Briquel ME, Cazenave JP. A three-base deletion removing a leucine residue in a leucine-rich repeat of platelet glycoprotein Ib alpha associated with a variant of Bernard-Soulier syndrome (Nancy I). Br J Haematol. 1995 Feb;89(2):386-96. PMID:7873390
6. ↑ Kenny D, Jonsson OG, Morateck PA, Montgomery RR. Naturally occurring mutations in glycoprotein Ibalpha that result in defective ligand binding and synthesis of a truncated protein. Blood. 1998 Jul 1;92(1):175-83. PMID:9639514
7. ↑ Koskela S, Partanen J, Salmi TT, Kekomaki R. Molecular characterization of two mutations in platelet glycoprotein (GP) Ib alpha in two Finnish Bernard-Soulier syndrome families. Eur J Haematol. 1999 Mar;62(3):160-8. PMID:10089893
8. ↑ Savoia A, Balduini CL, Savino M, Noris P, Del Vecchio M, Perrotta S, Belletti S, Poggi, Iolascon A. Autosomal dominant macrothrombocytopenia in Italy is most frequently a type of heterozygous Bernard-Soulier syndrome. Blood. 2001 Mar 1;97(5):1330-5. PMID:11222377
9. ↑ Matsubara Y, Murata M, Sugita K, Ikeda Y. Identification of a novel point mutation in platelet glycoprotein Ibalpha, Gly to Ser at residue 233, in a Japanese family with platelet-type von Willebrand disease. J Thromb Haemost. 2003 Oct;1(10):2198-205. PMID:14521605
10. ↑ Miller JL, Cunningham D, Lyle VA, Finch CN. Mutation in the gene encoding the alpha chain of platelet glycoprotein Ib in platelet-type von Willebrand disease. Proc Natl Acad Sci U S A. 1991 Jun 1;88(11):4761-5. PMID:2052556
11. ↑ Murata M, Russell SR, Ruggeri ZM, Ware J. Expression of the phenotypic abnormality of platelet-type von Willebrand disease in a recombinant glycoprotein Ib alpha fragment. J Clin Invest. 1993 May;91(5):2133-7. PMID:8486780 doi:http://dx.doi.org/10.1172/JCI116438
12. ↑ Russell SD, Roth GJ. Pseudo-von Willebrand disease: a mutation in the platelet glycoprotein Ib alpha gene associated with a hyperactive surface receptor. Blood. 1993 Apr 1;81(7):1787-91. PMID:8384898
13. ↑ Allen S, Abuzenadah AM, Hinks J, Blagg JL, Gursel T, Ingerslev J, Goodeve AC, Peake IR, Daly ME. A novel von Willebrand disease-causing mutation (Arg273Trp) in the von Willebrand factor propeptide that results in defective multimerization and secretion. Blood. 2000 Jul 15;96(2):560-8. PMID:10887119
14. ↑ Bodo I, Katsumi A, Tuley EA, Eikenboom JC, Dong Z, Sadler JE. Type 1 von Willebrand disease mutation Cys1149Arg causes intracellular retention and degradation of heterodimers: a possible general mechanism for dominant mutations of oligomeric proteins. Blood. 2001 Nov 15;98(10):2973-9. PMID:11698279
15. ↑ Fukuda K, Doggett T, Laurenzi IJ, Liddington RC, Diacovo TG. The snake venom protein botrocetin acts as a biological brace to promote dysfunctional platelet aggregation. Nat Struct Mol Biol. 2005 Feb;12(2):152-9. Epub 2005 Jan 16. PMID:15665869 doi:10.1038/nsmb892