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Integrin beta 1 cytoplasmic domain dominant negative effects revealed by lysophosphatidic acid treatment
L Smilenov1, R Briesewitz, E E Marcantonio
1Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
Insights
A novel chimeric protein (IL2R-beta 1) disrupts integrin-cytoskeleton connections, acting as a dominant negative effector. This impacts cell adhesion, particularly during cytoskeletal reorganization, highlighting the beta 1 cytoplasmic domain's crucial role.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Integrin receptors are key for cell adhesion, linking the extracellular matrix to the cytoskeleton via their beta 1 cytoplasmic domain.
- Understanding the beta 1 cytoplasmic domain's function is crucial for deciphering cell adhesion mechanisms.
Purpose of the Study:
- To investigate the role of the integrin beta 1 cytoplasmic domain in cell adhesion and cytoskeletal interaction.
- To create a tool to uncouple adhesion from intracellular signaling events.
Main Methods:
- Engineered a chimeric protein (IL2R-beta 1) combining interleukin 2 receptor alpha subunit domains with the integrin beta 1 cytoplasmic domain.
- Expressed IL2R-beta 1 in NIH 3T3 cells and assessed cell adhesion to fibronectin (FN).
- Induced cytoskeletal reorganization with lysophosphatidic acid (LPA) and observed effects on adhesion, with and without cytochalasin D.
Main Results:
- The IL2R-beta 1 chimera localized to focal contact sites but did not initially impair fibronectin adhesion.
- IL2R-beta 1 expressing cells detached from fibronectin upon LPA-induced cytoskeletal rearrangement, unlike wild-type cells.
- Cytochalasin D prevented LPA-induced detachment in IL2R-beta 1 cells, indicating a role for actin polymerization.
Conclusions:
- The uncoupled beta 1 cytoplasmic domain (in IL2R-beta 1) competes for cytoskeletal proteins, disrupting native integrin-cytoskeleton connections.
- The IL2R-beta 1 protein functions as a dominant negative effector, impairing cell adhesion under specific cellular conditions.
- This study elucidates the critical role of the integrin beta 1 cytoplasmic domain in maintaining stable cell adhesion through cytoskeletal linkage.
Abstract:
Integrin receptors localize to focal contact sites and interact with the cytoskeleton via the beta 1 cytoplasmic domain. To study the role of this domain in adhesion, we have expressed in NIH 3T3 cells a cDNA consisting of the interleukin 2 receptor alpha subunit extracellular and transmembrane domains, connected to the integrin beta 1 cytoplasmic domain (IL2R-beta 1). Since the extracellular domain of the chimeric protein has no role in adhesion, this protein could uncouple adhesion from intracellular events. As expected, in a cell line expressing IL2R-beta 1, this chimera was directed to focal contact sites. Unexpectedly, the cells exhibited normal adhesion to fibronectin (FN). However, when a rapid reorganization of the cytoskeleton was induced using lysophosphatidic acid (LPA), IL2R-beta 1 cells detached from FN in contrast to wild-type cells. The detachment in response to LPA could be prevented with cytochalasin D, an inhibitor of actin polymerization. These results imply that a beta 1 cytoplasmic domain, which is uncoupled from adhesion, can compete with the cytoplasmic domain of native integrin beta 1 for cytoskeletal proteins. As a consequence, the IL2R-beta 1 protein acts as a dominant negative effector of adhesion by disrupting the integrin-cytoskeleton connection.