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Integrins interact with focal adhesions through multiple distinct pathways
F S David1, P E Zage, E E Marcantonio
1Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York, USA.
Abstract:
Integrin signaling involves oligomerization and a transmembrane conformational change induced by receptor occupancy. Previous work has shown that subsets of focal adhesion-associated proteins are recruited to integrins as a result of clustering, ligand binding, or both. However, it is unclear whether these discrete subsets reflect the differential binding of cytoplasmic proteins to the integrin or whether a single protein or set of proteins binds the integrin and is differentially activated by receptor occupancy or clustering. To address this question, we made mutations of the beta1 integrin cytoplasmic domain in the context of a single subunit chimera and studied their activation of various known integrin-mediated signaling pathways. We show here that the indirect association of the integrin with actin is distinct from its interactions with both preformed focal adhesions and FAK. Therefore, multiple independent signaling pathways exist from the integrin to the focal adhesion, which may reflect the association of independent factors with the integrin beta1 cytoplasmic domain.
Insights
Integrin signaling involves multiple pathways. This study shows distinct protein interactions with the beta1 integrin cytoplasmic domain, revealing independent signaling routes to focal adhesions.
Area of Science:
- Cell biology
- Molecular biology
- Biochemistry
Background:
- Integrin signaling is crucial for cell adhesion and migration.
- Receptor occupancy and clustering induce integrin conformational changes.
- Focal adhesion proteins are recruited to integrins, but the mechanism is unclear.
Purpose of the Study:
- To investigate whether distinct cytoplasmic proteins bind to integrins or if a single protein is differentially activated.
- To elucidate the signaling pathways from integrin beta1 to focal adhesions.
Main Methods:
- Mutagenesis of the beta1 integrin cytoplasmic domain.
- Analysis of integrin-mediated signaling pathways using single subunit chimeras.
Main Results:
- The association of integrins with actin is independent of their interaction with focal adhesions and focal adhesion kinase (FAK).
- Multiple, distinct signaling pathways originate from the integrin beta1 cytoplasmic domain.
Conclusions:
- Integrin beta1 cytoplasmic domain interacts with distinct protein subsets.
- Independent signaling pathways mediate integrin-to-focal adhesion communication.