title: Integrin-αIIbβ3-mediated outside-in signalling activates a negative feedback pathway to suppress platelet activation.
abstract: Integrin-αIIbβ3-mediated outside-in signalling is widely accepted as an amplifier of platelet activation; accumulating evidence suggests that outside-in signalling can, under certain conditions, also function as an inhibitor of platelet activation. The role of integrin-αIIbβ3-mediated outside-in signalling in platelet activation is disputable. We employed flow cytometry, aggregometry, immunoprecipitation, and immunoblotting to investigate the role of integrin-αIIbβ3-mediated outside-in signalling in platelet activation. Integrin αIIbβ3 inhibition enhances agonist-induced platelet ATP secretion. Human platelets lacking expression of αIIbβ3 exhibited more platelet ATP secretion than their wild-type counterparts. Moreover, integrin-αIIbβ3-mediated outside-in signals activate SHIP-1, which in turn mediates p-Akt dephosphorylation, leading to inactivation of PI3K/Akt signalling. Furthermore, 3AC (SHIP-1 inhibitor) inhibits platelet disaggregation, and promotes platelet ATP secretion. Upon ADP stimulation, Talin is recruited to αIIbβ3, and it is dissociated from αIIbβ3 when platelets disaggregate. In addition, treatment with RUC2, an inhibitor of αIIbβ3, which blocks αIIbβ3-mediated outside-in signalling, can markedly prevent the dissociation of talin from integrin. SHIP1 Inhibitor 3AC inhibits the dissociation of talin from integrin-β3. These results suggest that integrin-αIIbβ3-mediated outside-in signalling can serve as a brake to restrict unnecessary platelet activation by activated SHIP-1, which mediated the disassociation of talin from β3, leading to integrin inactivation and blocking of PI3K/Akt signalling to restrict platelet ATP secretion.
authors.forename: Baiyun
authors.initials: B
authors.lastname: Dai
authors.forename: Peng
authors.initials: P
authors.lastname: Wu
authors.forename: Feng
authors.initials: F
authors.lastname: Xue
authors.forename: Renchi
authors.initials: R
authors.lastname: Yang
authors.forename: Ziqiang
authors.initials: Z
authors.lastname: Yu
authors.forename: Kesheng
authors.initials: K
authors.lastname: Dai
authors.forename: Changgeng
authors.initials: C
authors.lastname: Ruan
authors.forename: Gang
authors.initials: G
authors.lastname: Liu
authors.affiliation: Peter J. Newman, PhD, Blood Research Institute, Blood Center of Wisconsin, Milwaukee, 53711 WI, USA, E-mail: Peter.Newman@bcw.edu.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Newman
authors.affiliation: Cunji Gao, PhD, Chronic Disease Research Institute, Department of Nutrition and Food Hygiene, Zhejiang University School of Public Health, 310058 Hangzhou, China, Tel: +86 571 882 066 00, Fax: +86 571 882 066 00, E-mail: gaocunji@zju.edu.cn.
authors.forename: Cunji
authors.initials: C
authors.lastname: Gao
mesh_terms: D001792:Blood Platelets; D006801:Humans; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases / Q000378:metabolism; D015539:Platelet Activation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D016608:Talin
chemical_list: D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D016608:Talin; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; C000606430:INPP5D protein, human; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases
keywords: ATP; Integrins; RGD-peptide; platelets; talin