Human β-Filamin Is a New Protein That Interacts with the Cytoplasmic Tail of Glycoprotein Ibα

• Published in: The Journal of biological chemistry Vol. 273; no. 28; pp. 17531 - 17538
• Main Authors: Takafuta, Toshiro, Wu, Guoxin, Murphy, George F., Shapiro, Sandor S.
• Format: Journal Article
• Language: English
• Published: 10.07.1998
• ISSN: 0021-9258
• DOI: 10.1074/jbc.273.28.17531

We have cloned and sequenced a 9.4-kilobase cDNA specifying a new 280-kDa protein interacting with the cytoplasmic tail of glycoprotein (Gp) Ib alpha and showing considerable homology to actin-binding protein 280 (ABP-280) and chicken retinal filamin. We term this protein human beta -filamin. The gene for beta -filamin localizes to chromosome 3p14.3-p21.1. beta -Filamin mRNA expression was observed in many tissues and in cultured human umbilical vein endothelial cells (HUVECs); only minimal expression was detected in platelets and the megakaryocytic cell line CHRF-288. Like ABP-280, beta -filamin contains an NH sub(2)-terminal actin-binding domain, a backbone of 24 tandem repeats, and two "hinge" regions. A polyclonal antibody to the unique beta -filamin first hinge sequence identifies a strong 280-kDa band in HUVECs but only a weak band in platelets, and stains normal human endothelial cells in culture and in situ. We have confirmed the interaction of beta -filamin and GpIb alpha in platelet and HUVEC lysates. In addition, using two-hybrid analysis with deletion mutants, we have localized the binding domain for GpIb alpha in beta -filamin to residues 1862-2148, an area homologous to the GpIb alpha binding domain in ABP-280. beta -Filamin is a new member of the filamin family that may have significance for GpIb alpha function in endothelial cells and platelets.