Format

Send to

Choose Destination
J Biol Chem. 2013 Oct 11;288(41):29621-32. doi: 10.1074/jbc.M113.474163. Epub 2013 Aug 30.

Procoagulant platelets form an α-granule protein-covered "cap" on their surface that promotes their attachment to aggregates.

Author information

1
From the Center for Theoretical Problems of Physicochemical Pharmacology, 119991 Moscow, Russia.

Abstract

Strongly activated "coated" platelets are characterized by increased phosphatidylserine (PS) surface expression, α-granule protein retention, and lack of active integrin αIIbβ3. To study how they are incorporated into thrombi despite a lack of free activated integrin, we investigated the structure, function, and formation of the α-granule protein "coat." Confocal microscopy revealed that fibrin(ogen) and thrombospondin colocalized as "cap," a single patch on the PS-positive platelet surface. In aggregates, the cap was located at the point of attachment of the PS-positive platelets. Without fibrin(ogen) retention, their ability to be incorporated in aggregates was drastically reduced. The surface fibrin(ogen) was strongly decreased in the presence of a fibrin polymerization inhibitor GPRP and also in platelets from a patient with dysfibrinogenemia and a fibrinogen polymerization defect. In contrast, a fibrinogen-clotting protease ancistron increased the amount of fibrin(ogen) and thrombospondin on the surface of the PS-positive platelets stimulated with collagen-related peptide. Transglutaminases are also involved in fibrin(ogen) retention. However, platelets from patients with factor XIII deficiency had normal retention, and a pan-transglutaminase inhibitor T101 had only a modest inhibitory effect. Fibrin(ogen) retention was normal in Bernard-Soulier syndrome and kindlin-3 deficiency, but not in Glanzmann thrombasthenia lacking the platelet pool of fibrinogen and αIIbβ3. These data show that the fibrin(ogen)-covered cap, predominantly formed as a result of fibrin polymerization, is a critical mechanism that allows coated (or rather "capped") platelets to become incorporated into thrombi despite their lack of active integrins.

KEYWORDS:

Fibrinogen; Integrin αIIbβ3; Phosphatidylserine; Platelet Aggregation; Platelets; Thrombospondin; Transglutaminases

PMID:
23995838
PMCID:
PMC3795260
DOI:
10.1074/jbc.M113.474163
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center