beta1-integrin cytoplasmic subdomains involved in dominant negative function.
The beta1-integrin cytoplasmic domain consists of a membrane proximal subdomain common to the four known isoforms ("common" region) and a distal subdomain specific for each isoform ("variable" region). To investigate in detail the role of these subdomains in integrin-dependent cellular functions, we used beta1A and beta1B isoforms as well as four mutants lacking the entire cytoplasmic domain (beta1TR), the variable region (beta1COM), or the common region (beta1 deltaCOM-B and beta1 deltaCOM-A). By expressing these constructs in Chinese hamster ovary and beta1 integrin-deficient GD25 cells (Wennerberg et al., J Cell Biol 132, 227-238, 1996), we show that beta1B, beta1COM, beta1 deltaCOM-B, and beta1 deltaCOM-A molecules are unable to support efficient cell adhesion to matrix proteins. On exposure to Mn++ ions, however, beta1B, but none of the mutants, can mediate cell adhesion, indicating specific functional properties of this isoform. Analysis of adhesive functions of transfected cells shows that beta1B interferes in a dominant negative manner with beta1A and beta3/beta5 integrins in cell spreading, focal adhesion formation, focal adhesion kinase tyrosine phosphorylation, and fibronectin matrix assembly. None of the beta1 mutants tested shows this property, indicating that the dominant negative effect depends on the specific combination of common and B subdomains, rather than from the absence of the A subdomain in the beta1B isoform.
Retta
S F
SF
Department of Genetics, Biology, and Medical Chemistry, University of Torino, 10126 Torino, Italy.
Balzac
F
F
Ferraris
P
P
Belkin
A M
AM
Fässler
R
R
Humphries
M J
MJ
De Leo
G
G
Silengo
L
L
Tarone
G
G
D000185:Actinin / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D016466:CHO Cells; D002448:Cell Adhesion / Q000502:physiology*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D039482:Integrin alpha5; D039564:Integrin alphaV; D019012:Integrin beta1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D039661:Integrin beta3; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D016608:Talin / Q000378:metabolism
D015703:Antigens, CD; D015815:Cell Adhesion Molecules; D005353:Fibronectins; D039482:Integrin alpha5; D039564:Integrin alphaV; D019012:Integrin beta1; D039661:Integrin beta3; D010980:Platelet Membrane Glycoproteins; D011994:Recombinant Proteins; D016608:Talin; D000185:Actinin; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse