Human beta-filamin is a new protein that interacts with the cytoplasmic tail of glycoprotein Ibalpha.
We have cloned and sequenced a 9.4-kilobase cDNA specifying a new 280-kDa protein interacting with the cytoplasmic tail of glycoprotein (Gp) Ibalpha 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 NH2-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 GpIbalpha in platelet and HUVEC lysates. In addition, using two-hybrid analysis with deletion mutants, we have localized the binding domain for GpIbalpha in beta-filamin to residues 1862-2148, an area homologous to the GpIbalpha binding domain in ABP-280. beta-Filamin is a new member of the filamin family that may have significance for GpIbalpha function in endothelial cells and platelets.
Takafuta
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Cardeza Foundation for Hematologic Research, Department of Medicine, Jefferson Medical College, Philadelphia, Pennsylvania 19107, USA.
Wu
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Murphy
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Shapiro
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D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics; D002874:Chromosome Mapping; D002893:Chromosomes, Human, Pair 3; D003285:Contractile Proteins / Q000737:chemistry / Q000235:genetics; D003593:Cytoplasm / Q000378:metabolism*; D018076:DNA, Complementary; D064448:Filamins; D006801:Humans; D007150:Immunohistochemistry; D008840:Microfilament Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000378:metabolism*; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D017386:Sequence Homology, Amino Acid
D002352:Carrier Proteins; D003285:Contractile Proteins; D018076:DNA, Complementary; C578661:FLNC protein, human; D064448:Filamins; D008840:Microfilament Proteins; D019038:Platelet Glycoprotein GPIb-IX Complex; D012333:RNA, Messenger