Activated Conformations of Very Late Activation Integrins Detected by a Group of Antibodies (HUTS) Specific for a Novel Regulatory
Region(355
425) of the Common 
1 Chain (*)
- Alfonso Luque(1),
- Manuel Gómez(2),
- Wilma Puzon(3),
- Yoshikazu Takada(3),
- Francisco Sánchez-Madrid(2) and
- Carlos Cabañas(1)(§)
- From the (1)Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense, 28040 Madrid, Spain, the
- (2)Servicio de Inmunología, Hospital de la Princesa-U.A.M., 28006 Madrid, Spain, and the
- (3)Department of Vascular Biology, The Scripps Research Institute, La Jolla, California 92037
- § To whom correspondence should be addressed: Departamento Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense, 28040 Madrid, Spain. Tel.: 34-1-3941382; Fax: 34-1-3941691.
Abstract
The very late activation antigens (VLA) or β1 integrins mediate cell attachment to different extracellular matrix proteins
and intercellular adhesions. The ligand binding activity of these adhesion receptors is not constitutive and can be regulated
by temperature, presence of extracellular divalent cations, stimulatory monoclonal antibodies (mAbs), and cellular activation.
We have generated three novel mAbs, HUTS-4, HUTS-7, and HUTS-21, recognizing specific epitopes on the common β1 subunit (CD29)
of VLA integrins whose expression correlates with the ligand binding activity of these heterodimeric glycoproteins. This correlation
has been demonstrated for several integrin heterodimers in different cell systems using a variety of extracellular and intracellular
stimuli for integrin activation. Thus, the presence of micromolar concentrations of extracellular Mn
, preincubation with the activating anti-β1 mAb TS2/16, and cell treatment with phorbol esters or calcium ionophores, induced
the expression of the HUTS β1 epitopes on T lymphoblasts. Using a panel of human-mouse β1 chimeric molecules, we have mapped
these epitopes to the 355-425 sequence of the β1 polypeptide. This segment represents therefore a novel regulatory region
of β1 that is exposed upon integrin activation. Interestingly, binding of HUTS mAbs to partially activated VLA integrins results
in maximal activation of these adhesion receptors and enhancement of cell adhesion to β1 integrin ligands collagen, laminin,
and fibronectin.
Footnotes
-
↵* This work was supported by grants from the Comunidad Autónoma de Madrid CAM 230/92 and Fondo de Investigaciones Sanitarias FIS 93/0157 (to C. C.), FIS 95/0212 and PB 92/0318 (to F. S. M.), and GM 47157 and GM 49899 (to Y. T.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 The abbreviations used are:
- VLA
-
very late activation antigen(s)
- mAb
-
monoclonal antibody
- PMSF
-
phenylmethylsulfonyl fluoride
- PAGE
-
polyacrylamide gel electrophoresis
- BSA
-
bovine serum albumin
- PBS
-
phosphate-buffered saline.
-
- Received June 13, 1995.
- Revision received October 31, 1995.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
