Integrin beta 1 cytoplasmic domain dominant negative effects revealed by lysophosphatidic acid treatment.
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.
Smilenov
L
L
Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
Briesewitz
R
R
Marcantonio
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EE
D016475:3T3 Cells; D000199:Actins / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism*; D015536:Down-Regulation; D005353:Fibronectins / Q000378:metabolism; D015870:Gene Expression; D019012:Integrin beta1; D016023:Integrins / Q000235:genetics / Q000378:metabolism*; D007376:Interleukin-2 / Q000378:metabolism; D008246:Lysophospholipids / Q000494:pharmacology*; D051379:Mice; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D000199:Actins; D005353:Fibronectins; D019012:Integrin beta1; D016023:Integrins; D007376:Interleukin-2; D008246:Lysophospholipids; D015375:Receptors, Interleukin-2; D011993:Recombinant Fusion Proteins; D015638:Cytochalasin D