Laminin regulates PI3K basal localization and activation to sustain STAT5 activation

Ren Xu, Virginia A. Spencer, Dinah Levy Groesser, Mina J. Bissell

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Extracellular matrix (ECM) is a key regulator of tissue morphogenesis and functional differentiation in the mammary gland. We showed recently that laminin-111 (LN1) together with prolactin induces β-casein expression in mammary epithelial cells (MECs) by sustaining STAT5 activation. Others have shown that Rac1 is required for integrin-mediated STAT5 activation, but molecules upstream of Rac1 remain to be elucidated. Here, we show that exposure to three-dimensional (3D) laminin-rich ECM (LrECM) gels changes the localization of phosphoinositide 3-kinase (PI3K) in MECs from diffuse to basal accompanied with the activation of PI3K-Rac1 signaling pathway. We show by co-immunoprecipitation that Rac1 associates with STAT5, and that LrECM treatment enhances this interaction. Blocking PI3K with LY294002 inhibits LrECM-dependent Rac1 activation, attenuates sustained STAT5 phosphorylation and blocks β-casein gene transcription. These results indicate that PI3K is a key mediator of the LN1-induced signaling cascade which controls the activity of transcription factors essential for tissue-specific gene expression.

Original languageEnglish
Pages (from-to)4315-4322
Number of pages8
JournalCell Cycle
Issue number21
StatePublished - Nov 1 2010

Bibliographical note

Funding Information:
We thank Dr. Masahiko Itoh (Dokkyo University Tochigi prefecture, Japan) for providing the ZO-1 antibody. The construct containing STAT5A 1*6 was a kind gift from Dr. Toshio Kitamura (University of Tokyo, Japan). This work was supported by grants from the US Department of Energy, the Office of Biological and Environmental Research (contract no. DE-AC02-05CH1123), a Low Dose Radiation Program and a Distinguished Fellow Award from the Office of Health and Environmental Research Health Effects Division (contract no. 03-76SF00098) to M.J.B., the National Cancer Institute (awards R01CA064786, U54CA126552 and U54CA112970 to M.J.B. and R01CA057621 to M.J.B. and Zena Werb), the US Department of Defense Medical and Materiel Command Innovator Award (contract no.W81XWH0810736 and W81XWH0510338) to M.J.B. and postdoctoral fellowships DAMD17-02-1-0441 to R.X. and W81XWH0410581 to V.A.S. and a post-doctoral fellowship to V.A.S. from the Canadian Institutes of Health Research.


  • Laminin
  • PI3K-Rac1 pathway
  • Polarity
  • Sustained STAT5 activation

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology


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