Targeting of cytoskeletal linker proteins to focal adhesion complexes is reduced in fibroblasts adhering to laminin-1 when compared to fibronectin.
Cellular interactions with the extracellular matrix determine to a large extent cell behavior, including cell migration. These interactions take place at specialized cellular structures, the focal adhesions, which have a substrate-specific morphology. To determine the molecular and functional relevance of this observation, the composition of isolated focal adhesions developed by fibroblasts adhering to fibronectin or laminin-1 was analyzed by indirect immunofluorescence and immunoblotting with or without stabilization of the structures by cross-linking. In the absence of cross-linking, integrins, talin, vinculin and, to a lower extent, paxillin remained associated with the focal adhesions formed on both substrates, indicating a tight association of these proteins with the extracellular matrix support. By contrast, alpha-actinin, FAK, and actin were apparently loosely maintained within focal adhesions and were found associated to these structures only after stabilization by cross-linking. Interestingly, although both substrates induced clustering and aggregation of all these proteins, their relative concentration, with the exception of alpha-actinin, was lower within the focal adhesions formed on laminin-1 than in those formed on fibronectin. Moreover, as assessed in migration assays, the locomotory speed of fibroblasts was higher on laminin-1 than on fibronectin. Altogether these results indicate that integrins involved in cellular interactions with fibronectin or laminin-1 trigger the formation of focal adhesion structures which differ by molecular organization, concentration in several adhesion plaque components, and function.
Sondermann
H
H
Institut II für Biochemie, Faculty of Medicine, Cologne, Germany.
Dogic
D
D
Pesch
M
M
Aumailley
M
M
D000185:Actinin / Q000032:analysis; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000032:analysis; D002460:Cell Line; D002465:Cell Movement; D003598:Cytoskeletal Proteins / Q000032:analysis; D003599:Cytoskeleton / Q000502:physiology*; D005109:Extracellular Matrix / Q000502:physiology; D005347:Fibroblasts / Q000502:physiology*; D005353:Fibronectins / Q000502:physiology*; D019084:Fluorescent Antibody Technique, Indirect; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D015151:Immunoblotting; D019012:Integrin beta1 / Q000032:analysis; D007797:Laminin / Q000502:physiology*; D051419:Paxillin; D010750:Phosphoproteins / Q000032:analysis; D011505:Protein-Tyrosine Kinases / Q000032:analysis; D016608:Talin / Q000032:analysis; D013997:Time Factors
D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D005353:Fibronectins; D019012:Integrin beta1; D007797:Laminin; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; D016608:Talin; D000185:Actinin; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human