Proline-rich Sequence-mediated Jak2 Association to the Prolactin Receptor Is Required but Not Sufficient for Signal Transduction

doi:10.1074/jbc.270.18.10664

Proline-rich Sequence-mediated Jak2 Association to the Prolactin Receptor Is Required but Not Sufficient for Signal Transduction (*)

From the (1) From INSERM Unite 344, Endocrinologie Moléculaire, Faculté de Médecine Necker, 156 rue de Vaugirard, 75730 Paris Cedex 15, France and
the (2) Department of Molecular Biology, Max-Planck Institute fur Biochemie, Am Klopferspitz 18A, 8033 Martinsried, Germany

^§To whom correspondence should be addressed: Tel.: 331 40 61 53 10; Fax: 331 43 06 04 43.

Abstract

The prolactin receptor (PRLR) belongs to the superfamily of cytokine/growth hormone/prolactin receptors. Members of this family do not contain a tyrosine kinase domain but are associated with cytoplasmic kinases of the Jak family. Here, we examine different mutants of the PRLR with respect to their ability to associate and activate the kinase Jak2 and the transcription factor Stat1. Moreover, using a biological assay system we are able to correlate these activities with activation of prolactin-responsive gene transcription. Our results indicate that interaction between Jak2 and PRLR requires a proline-rich sequence in the membrane proximal region of the receptor, which is conserved among the different members of the cytokine receptor superfamily. We also show that association of Jak2 with the receptor is sufficient for activation of the kinase as well as the transcription factor Stat1. Moreover, our findings indicate that association of PRLR with Jak2 is necessary but not sufficient for the transmission of a lactogenic signal. We have identified two other cytoplasmic regions of the PRLR that are required for activation of transcription. These two regions are located between boxes 1 and 2 and are in the carboxyl-terminal tail of the receptor. These sites probably involve specific interactions with other effector molecules.

Footnotes

↵* This research was supported in part by grants from INSERM, the Fonds de Recherches en Santé du Québec, and the Medical Research Council of Canada. 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:

PRLR

prolactin receptor

oPRL

ovine prolactin

IL-2Rβ

β subunit of the interleukin-2 receptor

GHR

growth hormone receptor

GM-CSFR

granulocyte macrophage-colony-stimulating factor receptor

gp 130

β-subunit of the IL-6R, leukemia inhibitory factor receptor

OSMR

oncostatin M receptor

CNTFR

ciliary neurotrophic factor receptor

EPOR

erythropoietin receptor

GM-CSFRβ

common β-subunit of the GM-CSFR, IL-3R, and IL-5R

aa

amino acids

DMEM

Dulbecco's modified Eagle's medium.