Identification of a novel, actin-rich structure, the actin nodule, in the early stages of platelet spreading

Calaminus, S.D.J., Thomas, S., McCarty, O. J. T., Machesky, L.M. and Watson, S. P. (2008) Identification of a novel, actin-rich structure, the actin nodule, in the early stages of platelet spreading. Journal of Thrombosis and Haemostasis, 6(11), pp. 1944-1952. (doi: 10.1111/j.1538-7836.2008.03141.x)

Abstract

Background: During platelet spreading, the actin cytoskeleton undergoes marked changes, forming filopodia, lamellipodia and stress fibres. In the present study, we report the identification of a novel actin-rich structure, termed an actin nodule, which appears prior to lamellipodia and stress fibre formation. Methods: Platelet spreading was monitored using human platelets and mouse GFP-actin platelets using real-time and end-point DIC, and fluorescent and electron microscopy (EM). Results: We identified a small, novel actin structure, the actin nodule, in the early stages of adhesion and spreading, which we hypothesize to be a precursor of lamellipodia and stress fibres. Nodule formation shows an inverse correlation to Rho kinase and myosin-II activity, is independent of PI3-kinase, but dependent on Src kinase activity. Actin nodules contain multiple proteins, including Arp2/3, Fyn, Rac, and beta 1- and beta 3- integrins, but not Src. EM analysis revealed that actin filaments extend in all directions from the nodules. Actin nodules are present on multiple matrices, including fibrinogen, laminin and VWF + botrocetin. Conclusion: This work identifies a novel platelet actin structure, which we propose is a precursor to both lamellipodia and stress fibres and acts to drive platelet spreading.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Calaminus, Dr Simon and Machesky, Professor Laura
• Authors: Calaminus, S.D.J., Thomas, S., McCarty, O. J. T., Machesky, L.M., and Watson, S. P.
• College/School: College of Medical Veterinary and Life Sciences > School of Cancer Sciences
• Journal Name: Journal of Thrombosis and Haemostasis
• ISSN: 15387933