OBJECTIVE Platelet stimulation by collagen and collagen-related peptides (CRPs) is associated with activation of protein tyrosine kinases. In the present study, we investigated the role of Src family tyrosine kinases in the initial adhesion events of human platelets to collagen and cross-linked CRP. METHODS AND RESULTS Under arterial flow conditions, a glycoprotein VI-specific substrate, cros...

The binding of collagen to platelet glycoprotein VI (GPVI) leads to the subsequent activation of phospholipase Cgamma2 through a pathway that is dependent on the Fc receptor gamma (FcR gamma) chain and the tyrosine kinase p72syk. We have investigated the role of platelet Src-family kinases in this signalling pathway. The selective Src-family kinase inhibitor PP1 prevented collagen-stimulated in...

Platelet responses to collagen are mediated by the combined actions of the integrin alpha2beta1, which serves as a major collagen-binding receptor, and the GPVI/FcRgamma-chain complex, which transmits collagen-specific activation signals into the cell interior through the action of an immunoreceptor tyrosine-based activation motif within the cytoplasmic domain of the FcRgamma-chain. Despite muc...

A library of eight conformation-dependent monoclonal antibodies that react with distinct epitopes on native human type III collagen has been examined for the ability of these antibodies to inhibit platelet aggregation induced by this collagen. Six of these antibodies had no effects; one, 1E7-D7/Col3, delayed the onset and slowed the rate of platelet aggregation, while another, 2G8-B1/Col3, comp...

Abstract The LIM domain-dependent localization of the adapter protein paxillin to β3 integrin-positive focal adhesions (FAs) is not mechanistically understood. Here, by combining molecular biology, photoactivation and FA-isolation experiments, we demonstrate specific contributions each domain reveal multiple interactions in adhesion-complexes. Mutation integrin at a putative binding site (β3 VE...

Collagen phagocytosis is a crucial alpha2beta1-integrin-dependent process that mediates extracellular matrix remodeling by fibroblasts. We showed previously that after initial contact with collagen, activated Rac1 accelerates collagen phagocytosis but the Rac guanine nucleotide exchange factors (GEFs) that regulate Rac are not defined. We examined here the GEFs that regulate collagen phagocytos...

The snake venom rhodocytin has been reported to bind to integrin alpha2beta1 and glycoprotein (GP) Ibalpha on platelets, but it is also able to induce activation independent of the 2 receptors and of GPVI. Using rhodocytin affinity chromatography, we have identified a novel C-type lectin receptor, CLEC-2, in platelets that confers signaling responses to rhodocytin when expressed in a cell line....

Platelets are essential for wound healing and inflammatory processes, but can also play a deleterious role by causing heart attack and stroke. Normal platelet activation is dependent on tetraspanins, a superfamily of glycoproteins that function as 'organisers' of cell membranes by recruiting other receptors and signalling proteins into tetraspanin-enriched microdomains. However, our understandi...

We found that the convergently epidermal growth factor (EGF)-induced signal and the collagen-induced signal activate mitogen-activated protein kinase (MAPK), which induces migration. We examined the signaling mechanisms of EGF-induced cell migration on collagen using the A431 carcinoma cell. EGF (10 ng/ml) induced migration on collagen, but inhibited proliferation. Using a MAPK cascade inhibito...

Bruton's tyrosine kinase (Btk) is essential for normal B-cell receptor signalling. The lack of expression of functional Btk in humans leads to the B-cell deficiency X-linked agammaglobulinaemia (XLA). We report here that Btk is also important for signalling via the collagen receptor glycoprotein VI (GPVI) in platelets. GPVI is coupled to the Fc receptor gamma chain (FcRgamma). The FcRgamma-chai...