Cytoskeletal Interactions with the Leukocyte Integrin β2 Cytoplasmic Tail
ACTIVATION-DEPENDENT REGULATION OF ASSOCIATIONS WITH TALIN AND α-ACTININ*
- From the Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis, Indiana 46202-5120
Abstract
Circulating leukocytes are nonadherent but bind tightly to endothelial cells following activation. The increased avidity of leukocyte integrins for endothelial ligands following activation is regulated, in part, by interaction of the β2 subunit cytoplasmic tail with the actin cytoskeleton. We propose a mechanism to explain how tethering of the actin cytoskeleton to leukocyte integrins is regulated. In resting leukocytes, β2 integrins are constitutively linked to the actin cytoskeleton via the protein talin. Activation of cells induces proteolysis of talin and dissociation from the β2 tail. This phase is transient, however, and is followed by reattachment of actin filaments to integrins that is mediated by the protein α-actinin. The association of α-actinin with integrins may stabilize the cytoskeleton and promote firm adhesion to and migration across the endothelium. Glutathione S-transferase-β2 tail fusion protein/mutagenesis experiments suggest that the affinity of α-actinin binding to the β2 tail is regulated by a change in the conformation of the tail that unmasks a cryptic α-actinin binding domain. Positive and inhibitory domains within the β2 tail regulate α-actinin binding: a single 11-amino acid region (residues 736–746) is necessary and sufficient for α-actinin binding, and a regulatory domain between residues 748–762 inhibits constitutive association of the β2 tail with α-actinin.
Footnotes
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↵* This work was supported by grants from the American Heart Association and National Institutes of Health Grants GM47333 and HL54118.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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↵‡ Present address: Isis Pharmaceuticals, Carlsbad, CA 92008.
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↵§ To whom correspondence should be addressed: Dept. of Physiology and Biophysics, Indiana University School of Medicine, 635 Barnhill Dr., MS 377, Indianapolis, IN 46202-5120. Tel.: 317-274-3140; Fax: 317-274-3318; E-mail: fpavalko{at}iupui.edu.
- Abbreviations:
- LFA-1
-
lymphocyte function-associated antigen-1
- GST
-
glutathioneS-transferase
- PMA
-
phorbol 12-myristate 13-acetate
- FMLP
-
formyl-methionyl-leucyl-phenylalanine
- PMN
-
polymorphonuclear leukocyte
- PBS
-
phosphate-buffered saline
- CHAPS
-
3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate
- w.t.
-
wild-type
- TBS
-
Tris-buffered saline.
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- Received August 13, 1998.
- Revision received September 17, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
