title: The actin binding proteins cortactin and HS1 are dispensable for platelet actin nodule and megakaryocyte podosome formation.
abstract: A dynamic, properly organised actin cytoskeleton is critical for the production and haemostatic function of platelets. The Wiskott Aldrich Syndrome protein (WASp) and Actin-Related Proteins 2 & 3 Complex (Arp2/3 complex) are critical mediators of actin polymerisation and organisation in many cell types. In platelets and megakaryocytes, these proteins have been shown to be important for proper platelet production and function. The cortactin family of proteins (Cttn & HS1) are known to regulate WASp-Arp2/3-mediated actin polymerisation in other cell types and so here we address the role of these proteins in platelets using knockout mouse models. We generated mice lacking Cttn and HS1 in the megakaryocyte/platelet lineage. These mice had normal platelet production, with platelet number, size and surface receptor profile comparable to controls. Platelet function was also unaffected by loss of Cttn/HS1 with no differences observed in a range of platelet function assays including aggregation, secretion, spreading, clot retraction or tyrosine phosphorylation. No effect on tail bleeding time or in thrombosis models was observed. In addition, platelet actin nodules, and megakaryocyte podosomes, actin-based structures known to be dependent on WASp and the Arp2/3 complex, formed normally. We conclude that despite the importance of WASp and the Arp2/3 complex in regulating F-actin dynamics in many cells types, the role of cortactin in their regulation appears to be fulfilled by other proteins in platelets.
authors: a Institute of Cardiovascular Sciences, Institute for Biomedical Research, The Medical School, University of Birmingham , Edgbaston , Birmingham , UK.
authors: Steven G
authors: http://orcid.org/0000-0001-8733-7842
authors: SG
authors: Thomas
authors: a Institute of Cardiovascular Sciences, Institute for Biomedical Research, The Medical School, University of Birmingham , Edgbaston , Birmingham , UK.
authors: Natalie S
authors: http://orcid.org/0000-0002-3187-2130
authors: NS
authors: Poulter
authors: a Institute of Cardiovascular Sciences, Institute for Biomedical Research, The Medical School, University of Birmingham , Edgbaston , Birmingham , UK.
authors: Danai
authors: D
authors: Bem
authors: a Institute of Cardiovascular Sciences, Institute for Biomedical Research, The Medical School, University of Birmingham , Edgbaston , Birmingham , UK.
authors: Brenda
authors: B
authors: Finney
authors: b Cancer Research UK Beatson Institute, College of Medical. Veterinary and Life Sciences , University of Glasgow , Glasgow , UK.
authors: Laura M
authors: http://orcid.org/0000-0002-7592-9856
authors: LM
authors: Machesky
authors: a Institute of Cardiovascular Sciences, Institute for Biomedical Research, The Medical School, University of Birmingham , Edgbaston , Birmingham , UK.
authors: Stephen P
authors: http://orcid.org/0000-0002-7846-7423
authors: SP
authors: Watson
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D051356:Cortactin / Q000378:metabolism*; D005260:Female; D016179:Granulocyte Colony-Stimulating Factor / Q000378:metabolism*; D006801:Humans; D008297:Male; D008533:Megakaryocytes / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D000069261:Podosomes / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D000199:Actins; D051356:Cortactin; C524015:hematopoietic lineage cell-specific protein 1, mouse; D016179:Granulocyte Colony-Stimulating Factor
keywords: Actin nodules; Cortactin; HS1; platelets; podosomes