Stat5 as a Target for Regulation by Extracellular Matrix

doi:10.1074/jbc.270.37.21639

Stat5 as a Target for Regulation by Extracellular Matrix (*)

From the (1) School of Biological Sciences, University of Manchester, Manchester M13 9PT, United Kingdom,
(2) Roslin Institute (Edinburgh) Roslin, Midlothian EH25 9PS, United Kingdom, and
the (3) Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York 10032

^§ Wellcome Senior Research Fellow in Basic Biomedical Science. To whom correspondence should be addressed. Tel.: 44 161 275 5626; Fax: 44 161 275 3915.

Abstract

Transcription of tissue-specific genes in mammary gland requires signals from both prolactin and basement membrane. Here we address the mechanism by which this specialized extracellular matrix regulates transcription. Using mammary cell cultures derived from transgenic mice harboring the ovine β-lactoglobulin gene, we show that either a basement membrane extract, or purified laminin-1, induced high levels of β-lactoglobulin synthesis. It is known that prolactin signals through Stat5 (signal transducer and activator of transcription). This transcription factor interacts with -interferon activation site-related motifs within the β-lactoglobulin promoter, which we show are required for matrix dependence of β-lactoglobulin expression. The DNA binding activity of Stat5 was present only in extracts of mammary cells cultured on basement membrane, indicating that the activation state of Stat5 is regulated by the type of substratum the cell encounters. Thus, basement membrane controls transcription of milk protein genes through the Stat5-mediated prolactin signaling pathway, providing a molecular explanation for previous studies implicating extracellular matrix in the control of mammary differentiation.

Footnotes

↵^¶ Supported by Wellcome Trust Grant 040944.
↵** Supported by the Biotechnology and Biological Sciences Research Council Stem Cell Molecular Biology Programme.
↵^§§ Biotechnology and Biological Sciences Research Council postdoctoral fellow.
↵* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

ECM

extracellular matrix

BLG

β-lactoglobulin

PBS

phosphate-buffered saline

CAT

chloramphenicol acetyltransferase

EHS

Engelbreth-Holm-Swarm

GAS

-interferon activation site

DMEM

Dulbecco's modified Eagle's medium

PAGE

polyacrylamide gel electrophoresis

kb

kilobase(s)

bp

base pair(s).
↵²J. Webster, R. M. Wallace, A. J. Clark, and C. B. Whitelaw, manuscript in preparation.
↵³J. Ashkenas, M. Bissell, and Z. Werb, personal communication.
↵⁴G. M. Edwards and C. H. Streuli, unpublished data.
↵⁵S. Pullan, J. Wilson, A. Metcalfe, G. M. Edwards, N. Goberdhan, J. Tilly, J. A. Hickman, C. Dive, and C. H. Streuli, submitted for publication.
- Received July 19, 1995.