GPIbα regulates platelet size by controlling the subcellular localization of filamin. Blood 2012 Mar 22;119(12):2906-13
Date
12/17/2011Pubmed ID
22174152Pubmed Central ID
PMC3327465DOI
10.1182/blood-2011-08-376566Scopus ID
2-s2.0-84858835276 (requires institutional sign-in at Scopus site) 48 CitationsAbstract
Interaction between the cytoplasmic domain of GPIbα with its cytoskeletal binding partner, filamin, is a major determinant of platelet size, and deficiency of either protein results in macrothrombocytopenia. To clarify the mechanism by which GPIbα-filamin interactions regulate platelet production, we manipulated the expression levels of filamin and GPIb in cultured embryonic stem cells (ESCs) that were subsequently differentiated into platelets. Knocking down filamins A and B resulted in the production of ESC-derived proplatelets with abnormally large swellings and proplatelet shafts that generated giant platelets in culture. Large platelets could also be generated by overexpressing GPIbα in ESCs, or by overexpressing in vivo a transgene encoding a chimeric protein containing the cytoplasmic domain of GPIbα. To identify the mechanism by which the GPIb:filamin ratio regulates platelet size, we manipulated filamin and GPIbα levels in HEK293T cells and examined the effects of overexpressing either protein on their ability to traffic to the cell periphery. Accumulation of either protein within the endoplasmic reticulum resulted in trapping of the other. Taken together, these data demonstrate that coordinated expression of GPIbα and filamin is required for efficient trafficking of either protein to the cell surface, and for production of normal-sized platelets.
Author List
Kanaji T, Ware J, Okamura T, Newman PJAuthor
Peter J. Newman PhD Professor in the Pharmacology and Toxicology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsBlood Platelets
Cell Differentiation
Contractile Proteins
Filamins
Flow Cytometry
Humans
Immunoblotting
Immunoprecipitation
Membrane Glycoproteins
Mice
Mice, Transgenic
Microfilament Proteins
Platelet Glycoprotein GPIb-IX Complex
Protein Transport
Thrombopoiesis