| 1. |
|
|
| 2. |
|
|
| 3. |
- Ferletta, Maria, et al.
(författare)
-
Opposing roles of integrin alpha6Abeta1 and dystroglycan in laminin-mediated extracellular signal-regulated kinase activation
- 2003
-
Ingår i: Molecular Biology of the Cell. - 1059-1524 .- 1939-4586. ; 14:5, s. 2088-2103
-
Tidskriftsartikel (refereegranskat)abstract
- Laminin-integrin interactions can in some settings activate the extracellular signal-regulated kinases (ERKs) but the control mechanisms are poorly understood. Herein, we studied ERK activation in response to two laminins isoforms (-1 and -10/11) in two epithelial cell lines. Both cell lines expressed beta1-containing integrins and dystroglycan but lacked integrin alpha6beta4. Antibody perturbation assays showed that both cell lines bound to laminin-10/11 via the alpha3beta1and alpha6beta1 integrins. Although laminin-10/11 was a stronger adhesion complex than laminin-1 for both cell lines, both laminins activated ERK in only one of the two cell lines. The ERK activation was mediated by integrin alpha6beta1 and not by alpha3beta1 or dystroglycan. Instead, we found that dystroglycan-binding domains of both laminin-1 and -10/11 suppressed integrin alpha6beta1-mediated ERK activation. Moreover, the responding cell line expressed the two integrin alpha6 splice variants, alpha6A and alpha6B, whereas the nonresponding cell line expressed only alpha6B. Furthermore, ERK activation was seen in cells transfected with the integrin alpha6A subunit, but not in alpha6B-transfected cells. We conclude that laminin-1 and -10/11 share the ability to induce ERK activation, that this is regulated by integrin alpha6Abeta1, and suggest a novel role for dystroglycan-binding laminin domains as suppressors of this activation.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Kikkawa, Yamato, et al.
(författare)
-
Laminin isoforms differentially regulate adhesion, spreading, proliferation, and ERK activation of beta1 integrin-null cells.
- 2004
-
Ingår i: Experimental Cell Research. - : Elsevier BV. - 1090-2422 .- 0014-4827. ; 300:1, s. 94-108
-
Tidskriftsartikel (refereegranskat)abstract
- The presence of many laminin receptors of the β1 integrin family on most cells makes it difficult to define the biological functions of other major laminin receptors such as integrin α6β4 and dystroglycan. We therefore tested the binding of a β1 integrin-null cell line GD25 to four different laminin variants. The cells were shown to produce dystroglycan, which based on affinity chromatography bound to laminin-1, -2/4, and -10/11, but not to laminin-5. The cells also expressed the integrin α6Aβ4A variant. GD25 β1 integrin-null cells are known to bind poorly to laminin-1, but we demonstrate here that these cells bind avidly to laminin-2/4, -5, and -10/11. The initial binding at 20 min to each of these laminins could be inhibited by an integrin α6 antibody, but not by a dystroglycan antibody. Hence, integrin α6Aβ4A of GD25 cells was identified as a major receptor for initial GD25 cell adhesion to three out of four tested laminin isoforms. Remarkably, cell adhesion to laminin-5 failed to promote cell spreading, proliferation, and extracellular signal-regulated kinase (ERK) activation, whereas all these responses occurred in response to adhesion to laminin-2/4 or -10/11. The data establish GD25 cells as useful tools to define the role integrin α6Aβ4A and suggest that laminin isoforms have distinctly different capacities to promote cell adhesion and signaling via integrin α6Aβ4A.
|
|
| 7. |
|
|
| 8. |
- Yu, Hao, et al.
(författare)
-
beta 1 Integrin and alpha-dystroglycan binding sites are localized to different laminin-G-domain-like (LG) modules within the laminin alpha 5 chain G domain
- 2003
-
Ingår i: Biochemical Journal. - 0264-6021. ; 371, s. 289-299
-
Tidskriftsartikel (refereegranskat)abstract
- Laminins are a group of extracellular-matrix proteins important in development and disease. They are heterotrimers, and specific domains in the different chains have specialized functions. The G domain of the alpha5 chain has now been produced in transfected mammalian cells as single modules and two tandem arrays, alpha5LG1-3 and alpha5LG4-5 (LG is laminin G domain-like.). Using these fragments we produced specific polyclonal antibodies functional in immunoblotting and immunofluorescence studies and in solid-phase assays. Both alpha5LG tandem arrays had physiologically relevant affinities for sulphated ligands such as heparin and sulphatides. Cells adhered to these fragments and acquired a spread morphology when plated on a5LG1-3. Binding of integrins alpha3beta1 and alpha6beta1 was localized to the alpha5LG1-3 modules, and a-dystroglycan binding was localized to the a5LG4-5 modules, thus locating these activities to different LG modules within the laminin a5 G domain. However, both these activities were of relatively low affinity, indicating that integrin-mediated cell adhesion to the laminin 10/11 alpha5G domain depends on contributions from the other chains of the heterotrimer and that high-affinity a-dystroglycan binding could be dependent on specific Ca2+-ion-co-ordinating amino acids absent from alpha5LG4-5.
|
|
| 9. |
- Yu, Hao
(författare)
-
Laminin G Domains, their Receptors, and Activation of Intracellular Pathways
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Basement membranes are sheet like structures underlying epithelial, endothelial, adipocytes, muscle and peripheral nerve cells. Laminins are an important family of basement membrane proteins implicated in various biological functions through their interactions with cell surface receptors. Laminins are trimers composed of a, b and g chains. Integrins, dystroglycan and other transmembrane glycoproteins such as syndecans have been identified as cell surface receptors for laminins. The regulation of these interactions is important for many biological processes including cell adhesion, proliferation, differentiation, migration, cell survival and angiogenesis. These diverse activities are likely to be mediated by receptors inducing intracellular signaling pathways. Many receptor-binding sites have been localized to the LG domains of the laminin a chains. Using recombinant proteins of laminin a5 chain, we localized integrin a3β1 and a6β1 binding sites to laminin a5LG1-3, and a-dystroglycan binding to laminin a5LG4-5. We found that recombinant laminin a4LG4-5 promoted endothelial cell adhesion through the interaction with integrin a3β1 and a6β1 but not integrin avβ3. Laminin-10/11 was shown to promote epithelial cell adhesion through the interaction with both integrin a3β1 and a6β1. Integrin a6Aβ1 could induce laminin-1 and laminin-10/11 mediated ERK activation. The dystroglycan-binding domains of both laminin-1 and laminin-10/11 suppressed integrin a6Aβ1 mediated ERK activation. These results indicate opposing roles of integrin a6Aβ1 and a-dystroglycan in laminin mediated the ERK activation. Laminin isoforms were also found to play different roles in regulating cell adhesion, spreading, proliferation and ERK activation through the interaction with integrin a6Aβ4. The importance of laminin a4 chain for angiongensis was studied using both in vitro and in vivo angiogenesis model systems. Laminin a4LG4-5 inhibited endothelial cell tube formation and wound closure. It also showed an inhibitory effect on angiogenesis. Using monoclonal antibodies produced by us, we found that both intact and proteolytically processed forms of the a4 chain exist in vivo.
|
|
| 10. |
|
|
