98%
921
2 minutes
20
Objective: The platelet receptor for von Willebrand factor, the glycoprotein Ib-IX (GPIb-IX) complex, mediates platelet adhesion at sites of vascular injury and transmits signals leading to platelet activation. von Willebrand factor/GPIb-IX interaction sequentially activates the Src family kinase Lyn (SFK), phosphoinositide 3-kinase (PI3K), and Akt, leading to activation of integrin α(IIb)β(3) and integrin-dependent stable platelet adhesion and aggregation. It remains unclear how Lyn activates the PI3K/Akt pathway after ligand binding to GPIb-IX.
Methods And Results: Using platelet-specific Rac1(-/-) mice and the Rac1 inhibitor NSC23766, we examined the role of Rac1 in GPIb-IX-dependent platelet activation. Rac1(-/-) mouse platelets and NSC23766-treated human platelets were defective in GPIb-dependent stable adhesion to von Willebrand factor under shear stress, integrin activation, thromboxane A(2) synthesis, and platelet aggregation. Interestingly, GPIb-induced activation of Rac1 and the guanine nucleotide exchange factor for Rac1, Vav, was abolished in both Lyn(-/-) and SFK inhibitor-treated platelets but was unaffected by the PI3K inhibitor LY294002, indicating that Lyn mediates activation of Vav and Rac1 independently of PI3K. Furthermore, GPIb-induced activation of Akt was abolished in Rac1-deficient platelets, suggesting that Rac1 is upstream of the PI3K/Akt pathway.
Conclusions: A Lyn-Vav-Rac1-PI3K-Akt pathway mediates von Willebrand factor-induced activation of integrin α(IIb)β(3) to promote GPIb-IX-dependent platelet activation.
Download full-text PDF |
Source |
---|---|
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3523182 | PMC |
http://dx.doi.org/10.1161/ATVBAHA.112.254920 | DOI Listing |
Virchows Arch
December 2021
Department of Plastic Surgery, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine malignancy of the skin. The cell of origin of MCC is thus far unknown and proposed cells of origin include Merkel cells, pro-/pre- or pre-B cells, epithelial stem cells, and dermal stem cells. In this study, we aimed to shed further light on the possibility that a subset of MCC tumors arise from epithelial stem cells of the skin by examining the expression of hair follicle and epidermal stem cell markers in MCC and normal human skin.
View Article and Find Full Text PDFAm J Med Genet A
June 2021
The Folkhaelsan Department of Medical Genetics, The Folkhaelsan Institute of Genetics and the Department of Medical and Clinical Genetics, Medicum, University of Helsinki, Helsinki, Finland.
J Transl Med
October 2020
Institute of Neurophysiology, Medical Faculty Mannheim, University Heidelberg, Heidelberg, Germany.
J Eur Acad Dermatol Venereol
February 2019
Department of Dermatology, Allergology and Venereology, Helsinki University Central Hospital, Helsinki, Finland.
Transplantation
January 2016
1 Transplantation Laboratory, University of Helsinki, Helsinki, Finland. 2 Department of surgery, Oulu University Central Hospital, Oulu, Finland. 3 Transplantation and Liver Surgery Unit, Helsinki University Central Hospital, Helsinki, Finland. 4 Division of Nephrology, Department of Medicine, Hels