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Integrin clustering mechanisms explored with a soluble alphaIIbbeta3 ectodomain construct. Biochim Biophys Acta 2004 Jul 01;1700(1):19-25

Date

06/24/2004

Pubmed ID

15210121

DOI

10.1016/j.bbapap.2004.03.011

Abstract

The purpose of this study was to test the hypothesis that residues critical for ligand- and temperature-induced clustering of integrin alphaIIbbeta3 are present on its extracellular domain. Sucrose density gradient sedimentation was used to examine the effects of ligand-mimetic peptides and physiological temperature on the oligomeric state of a soluble recombinant ectodomain variant of the alphaIIbbeta3 integrin, alphaIIbDelta962beta3Delta692, and its full-length counterpart. Both the ectodomain construct, isolated from High Five insect cell culture supernatants, and alphaIIbbeta3, isolated from human blood platelets, exhibited similar weight-average sedimentation coefficients at 23 degrees C, in the absence and presence of the ligand-mimetic peptide eptifibatide. These observations indicate that alphaIIbbeta3's ectodomain exhibits a similar extended conformation in both its free and ligand-bound states. Oligomerization was examined by incubation of both alphaIIbDelta962beta3Delta692 and full-length receptors at 37 degrees C, in the presence or absence of ligand-mimetic. Minimal oligomerization was observed with alphaIIbDelta962beta3Delta692. In contrast, full-length alphaIIbbeta3 exhibited substantial temperature-induced increases in its distribution of sedimenting species, indicative of thermal aggregation. These observations suggest that optimum oligomerization requires the participation of the integrin's transmembrane and cytoplasmic regions. In vivo, clustering of ligand-bound integrins may enhance signaling by increasing the local concentration of intracellular integrin-associated proteins.

Author List

Hantgan RR, Gibbs W, Stahle MC, Aster RH, Peterson JA

Author

Richard H. Aster MD Professor in the Medicine department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Animals
Blood Platelets
Cell Line
Centrifugation, Density Gradient
Chromatography, Affinity
Insecta
Ligands
Platelet Glycoprotein GPIIb-IIIa Complex
Protein Denaturation
Protein Structure, Quaternary
Protein Structure, Tertiary
Solubility
Solutions
Temperature
jenkins-FCD Prod-387 b0ced2662056320369de4e5cd5f21c218c03feb3