A role for adhesion and degranulation-promoting adapter protein in collagen-induced platelet activation mediated via integrin α(2) β(1).

Abstract

BACKGROUND:

Collagen-induced platelet activation is a key step in the development of arterial thrombosis via its interaction with the receptors glycoprotein (GP)VI and integrin α(2) β(1) . Adhesion and degranulation-promoting adapter protein (ADAP) regulates α(IIb) β(3) in platelets and α(L) β(2) in T cells, and is phosphorylated in GPVI-deficient platelets activated by collagen.

OBJECTIVES:

To determine whether ADAP plays a role in collagen-induced platelet activation and in the regulation and function of α(2) β(1).

METHODS:

Using ADAP(-/-) mice and synthetic collagen peptides, we investigated the role of ADAP in platelet aggregation, adhesion, spreading, thromboxane synthesis, and tyrosine phosphorylation.

RESULTS AND CONCLUSIONS:

Platelet aggregation and phosphorylation of phospholipase Cγ2 induced by collagen were attenuated in ADAP(-/-) platelets. However, aggregation and signaling induced by collagen-related peptide (CRP), a GPVI-selective agonist, were largely unaffected. Platelet adhesion to CRP was also unaffected by ADAP deficiency. Adhesion to the α(2) β(1) -selective ligand GFOGER and to a peptide (III-04), which supports adhesion that is dependent on both GPVI and α(2) β(1), was reduced in ADAP(-/-) platelets. An impedance-based label-free detection technique, which measures adhesion and spreading of platelets, indicated that, in the absence of ADAP, spreading on GFOGER was also reduced. This was confirmed with non-fluorescent differential-interference contrast microscopy, which revealed reduced filpodia formation in ADAP(-/-) platelets adherent to GFOGER. This indicates that ADAP plays a role in mediating platelet activation via the collagen-binding integrin α(2) β(1). In addition, we found that ADAP(-/-) mice, which are mildly thrombocytopenic, have enlarged spleens as compared with wild-type animals. This may reflect increased removal of platelets from the circulation.

• Authors: G E Jarvis, D Bihan, S Hamaia, N Pugh, C J G Ghevaert, A C Pearce, C E Hughes, S P Watson, J Ware, C E Rudd, R W Farndale
• Journal: Journal of thrombosis and haemostasis : JTH (J Thromb Haemost) Vol. 10 Issue 2 Pg. 268-77 (Feb 2012) ISSN: 1538-7836 [Electronic] England
• PMID: 22103309 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2011 International Society on Thrombosis and Haemostasis.

Chemical References

• Adaptor Proteins, Signal Transducing
• CD36 Antigens
• Carrier Proteins
• Fyb protein, mouse
• Immunoglobulin Variable Region
• Integrin alpha2beta1
• Peptides
• Platelet Glycoprotein GPIIb-IIIa Complex
• collagen-related peptide
• Tyrosine
• Thromboxane B2
• Thromboxane A2
• Collagen
• Phospholipase C gamma

Topics

• Adaptor Proteins, Signal Transducing (deficiency, genetics, metabolism)
• Animals
• Blood Platelets (metabolism)
• CD36 Antigens (genetics, metabolism)
• Carrier Proteins (metabolism)
• Collagen (metabolism)
• Immunoglobulin Variable Region (genetics, metabolism)
• Integrin alpha2beta1 (metabolism)
• Mice
• Mice, Inbred C57BL
• Mice, Knockout
• Peptides (metabolism)
• Phospholipase C gamma (metabolism)
• Phosphorylation
• Platelet Activation
• Platelet Adhesiveness
• Platelet Aggregation
• Platelet Glycoprotein GPIIb-IIIa Complex (metabolism)
• Pseudopodia (metabolism)
• Splenomegaly (genetics, metabolism)
• Thrombocytopenia (genetics, metabolism)
• Thromboxane A2 (metabolism)
• Thromboxane B2 (metabolism)
• Time Factors
• Tyrosine