Abstract
To investigate a role of phospholipase C (PLC) isozymes in the integrin alphaIIbbeta3-mediated signaling, their location was examined in thrombin-activated human platelets, revealing different regulation of their translocation to the cytoskeleton (CSK). In resting platelets, the major PLCs such as PLCbeta2, PLCbeta3a (155 kDa), and PLCgamma2 and the minor PLCs (PLCbeta1 and PLCgamma1) were located in the Triton X-100-soluble (Tx.Sol) fraction and the membrane skeleton, whereas PLCbeta3b (140 kDa) was present only in Tx.Sol fraction when examined by Western immunoblotting. Thrombin stimulation caused a rapid and transient translocation of PLCbeta3a and PLCbeta3b and a slower accumulation of PLCbeta2 and PLCgamma2 in the reorganized CSK. The translocation to CSK of both PLCbeta3a and PLCbeta3b, but not PLCbeta2, was dependent on integrin alphaIIbbeta3-mediated aggregation. Furthermore, an actin polymerization inhibitor, cytochalasin D, or a protein tyrosine kinase inhibitor, genistein, abolished the CSK association of alphaIIbbeta3, PLCbeta3a, and PLCbeta3b. In the genistein-pretreated platelets, pp60(c-)src, Gq, and protein kinase Calpha were no longer able to associate with CSK. In contrast, these agents had no or marginal inhibitory effects on the CSK association of PLCbeta2 and Gi2. The late diacylglycerol generation induced by thrombin stimulation was significantly reduced by the genistein treatment. These results suggest that the integrin alphaIIbbeta3-mediated cytoskeletal association of PLCbeta3 is regulated by protein tyrosine kinase and also that the activation of the relocated PLC may play a role in the late platelet-to-platelet aggregation in thrombin-stimulated human platelets.
Highlights
Various protein tyrosine kinases including pp60c-src become associated with integrins through interactions with cytoskeletal complexes induced by integrin-dependent cytoskeletal reorganization [11,12,13,14,15]
Distribution of phospholipase C (PLC) Isozymes in Human Platelets with or without Thrombin Stimulation—We have previously demonstrated that human platelets contained two PLC3 forms that are different in molecular mass (PLC3a, 155 kDa and PLC3b, 140 kDa) when analyzed by using the Ab-PLC3C
The agonist stimulation causes activation of ␣IIb3 integrin by unique signal transduction, and the subsequent fibrinogen binding to the ␣IIb3 integrin, leading to cytoskeletal rearrangement and platelet aggregation, causes tyrosine kinase activation including pp125FAK and pp60c-src [1, 3, 4, 27]
Summary
Various protein tyrosine kinases including pp60c-src become associated with integrins through interactions with cytoskeletal complexes induced by integrin-dependent cytoskeletal reorganization [11,12,13,14,15]. This study was undertaken to examine the CSK association of different PLC isozymes and the regulatory mechanisms of the cytoskeletal reorganization that occur as a consequence of integrin-ligand interaction in thrombin-stimulated human platelets. Regulation of Cytoskeletal Association of PLC Isozymes— Aggregation requires fibrinogen binding to the activated integrin ␣IIb3 in thrombin-stimulated platelets [2,3,4,5].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
