Integrin adhesion receptors transduce signals that control complex cell fun
ctions which require the regulation of gene expression, such as proliferati
on, differentiation and survival(1). Their intracellular domain has no cata
lytic function, indicating that interaction with other transducing molecule
s is crucial for integrin-mediated signalling. Here we have identified a pr
otein that interacts with the cytoplasmic domain of the beta 2 subunit of t
he alpha L/beta 2 integrin LFA-1. This protein is JAB1 (Jun activation doma
in-binding protein 1), a coactivator of the c-Jun transcription factor(2).
We found that JAB1 is present both in the nucleus and in the cytoplasm of c
ells and that a fraction of JAB1 colocalizes with LFA-1 at the cell membran
e. LFA-1 engagement is followed by an increase of the nuclear pool of JAB1,
paralleled by enhanced binding of c-Jun-containing AP-1 complexes to their
DNA consensus site and increased transactivation of an AP-1-dependent prom
oter. We suggest that signalling through the LFA-1 integrin may affect c-Ju
n-driven transcription by regulating JAB1 nuclear localization. This repres
ents a new pathway for integrin-dependent modulation of gene expression.