Role of Actin-binding Protein in Insertion of Adhesion Receptors into the Membrane*
- From the ‡Joseph J. Jacobs Center for Thrombosis and Vascular Biology, Cleveland Clinic Foundation, Cleveland, Ohio 44195, the §Children’s Hospital Oakland Research Institute, Oakland, California 94609, and the ¶Gladstone Institute of Cardiovascular Disease, San Francisco, California 94141
Abstract
The goal of this study was to determine whether actin-binding protein (ABP) regulates membrane composition. ABP-deficient and ABP-containing cells were transfected with the cDNAs coding for glycoprotein (GP) Ib-IX, a platelet receptor that interacts with ABP. Most of the GP Ib-IX remained inside the ABP-deficient cells. When ABP was present, functional GP Ib-IX was inserted into the membrane. GP Ib-IX lacking the domain that interacts with ABP also showed increased membrane insertion in ABP-expressing cells. Furthermore, a fragment of ABP that lacks the dimerization and GP Ib-IX-binding sites restored the spreading of the cells and increased the amount of GP Ib-IX in the membrane. Finally, expression of ABP also increased endogenous β1 integrin in the membrane. These results indicate that 1) ABP maintains the properties of the cell such that adhesion receptors can be efficiently expressed in the membrane; 2) increased receptor expression is accompanied by increased ability of the cell to spread; and 3) ABP exerts its effect by a mechanism that does not appear to involve direct cross-linking of actin filaments or direct interaction with receptors.
Footnotes
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↵* This work was supported by National Institutes of Health Research Grant HL30657 (to J. E. B. F.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‖ To whom correspondence should be addressed: Joseph J. Jacobs Center for Thrombosis and Vascular Biology (FF 20), Cleveland Clinic Foundation, 9500 Euclid Ave., Cleveland, OH 44195. Tel.: 216-445-3874; Fax: 216-445-2051.
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↵1 The abbreviations used are: ABP, actin-binding protein; GP, glycoprotein; mAb, monoclonal antibody; FACS, fluorescence-activated cell sorting.
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- Received October 15, 1997.
- The American Society for Biochemistry and Molecular Biology, Inc.
