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Hong, Felix

University of British Columbia

Platelets are critical mediators of hemostasis and thrombosis. Platelets circulate as discs in their resting form but change shape rapidly upon activation by vascular damage and/or soluble agonists such as thrombin. The platelets’ shape change reaction is driven by a dynamic remodeling of the actin cytoskeleton. The actin filaments interact with the myosin protein, which is phosphorylated on the myosin light chain (MLC) upon platelet activation. The actin-myosin interaction triggers the contraction of the actin cytoskeleton, which drives platelet spreading and contractile force generation. Filamin A (FLNA) is an actin crosslinking protein that stabilizes the attachment between the subcortical actin filaments and the cell membrane. In addition, FLNA binds multiple proteins and serves as a critical intracellular signaling scaffold. Here, we used platelets from mice with a megakaryocyte/platelet-specific deletion of FLNA to investigate the role of FLNA in regulating the platelet shape change reaction. Relative to controls, FLNA-null platelets exhibited defective spreading, clot retraction, contraction force generation and MLC phosphorylation in response to thrombin stimulation. Blockade of Rho kinase (ROCK) and protein kinase C (PKC) with the inhibitors Y27632 and BIM also attenuated MLC phosphorylation; ROCK and PKC promote MLC phosphorylation through independent pathways. Notably, the activity of both ROCK and PKC were diminished in the FLNA-deficient platelets. We conclude that FLNA regulates thrombin-induced MLC phosphorylation and platelet contraction, in a ROCK- and PKC-dependent manner.

Text

2024-10-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/86227

Biochemistry and Molecular Biology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/