Investigation of the roles of the actin cytoskeleton remodelling proteins coronin and CAP1 in platelet function

Riley, David R. J.

Abstract

Platelets undergo profound rapid F-actin cytoskeleton remodeling and experience morphological and functional changes in response to receptor-mediated signaling from damaged blood vessel walls. The evolutionarily conserved proteins coronin 1 and adenylyl cyclase-associated protein 1 (CAP1) regulate the F-actin cytoskeleton and participate in signaling events. They are abundant in platelets but until recently their roles were poorly understood. Subcellular fractionation found coronin 1 is mainly cytosolic, but a significant amount associates with membranes in an actin- independent manner and does not translocate to or from the membrane upon platelet stimulation or inhibition. Coronin 1, 2 and 3 associate with the Triton insoluble cytoskeleton upon platelet stimulation. Immunostainings of spread platelets revealed that coronin 1, 2 and 3 demonstrate strong accumulation at F- actin nodules and display diffuse cytoplasmic localisation with discontinuous accumulation at the cell cortex. This is consistent with the role of coronins as integrators of extracellular signals with actin remodeling. Ablation of coronin 1 in platelets is associated with impaired translocation of integrin β2 to the cell surface upon stimulation with thrombin. However, morphological and functional defects are absent including Arp2/3 complex translocation, VASP phosphorylation, spreading ability, secretion, basal receptor levels, αIIbβ3 activation and haemostasis. While integrin β2 translocation appears specifically or predominantly dependent on coronin 1, the lack of other phenotypes suggests a high extent of functional overlap and redundancy among coronins 1, 2 and 3 in platelets. Subcellular fractionation found that ~20% of CAP1 is membrane-associated in an F-actin independent manner. Immunostainings demonstrated that in basal platelets CAP1 is mostly cortical whereas stimulation results in translocation to the cytosol in a significant proportion of platelets which can be inhibited by prostacyclin or nitric oxide. This places CAP1 at a crossroad of signalling pathways that controls platelet activation by contributing to actin remodelling at the cell cortex and actin nodules during platelet spreading.

Citation

Riley, D. R. J. Investigation of the roles of the actin cytoskeleton remodelling proteins coronin and CAP1 in platelet function. (Thesis). Hull York Medical School, the University of Hull and the University of York. https://hull-repository.worktribe.com/output/4223044

• Thesis Type: Thesis
• Deposit Date: Apr 7, 2021
• Publicly Available Date: Feb 23, 2023
• Keywords: Medical sciences
• Public URL: https://hull-repository.worktribe.com/output/4223044
• Additional Information: Hull York Medical School, The University of Hull and the University of York
• Award Date: Jun 1, 2020