The Janus kinase 2 is required for expression and nuclear accumulation of cyclin D1 in proliferating mammary epithelial cells

Kazuhito Sakamoto, Bradley A. Creamer, Aleata A. Triplett, Kay Uwe Wagner

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

Using a conditional knockout approach, we previously demonstrated that the Janus kinase 2 (Jak2) is crucial for prolactin (PRL) signaling and normal mammary gland development. PRL is suggested to synchronously activate multiple signaling cascades that emerge on the PRL receptor (PRLR). This study demonstrates that Jak2 is essential for the activation of the signal transducer and activator of transcription 5 (Stat5) and expression of Cish (cytokine-inducible SH2-containing protein), a Stat5-responsive negative regulator of Jak/Stat signaling. However, Jak2 is dispensable for the PRL-induced activation of c-Src, focal adhesion kinase, and the MAPK pathway. Despite activation of these kinases that are commonly associated with proliferative responses, the ablation of Jak2 reduces the multiplication of immortalized mammary epithelial cells (MECs). Our studies show that signaling through Jak2 controls not only the transcriptional activation of the Cyclin D1 gene, but, more importantly, it regulates the accumulation of the Cyclin D1 protein in the nucleus by altering the activity of signal transducers that mediate the phosphorylation and subsequent nuclear export of Cyclin D1. In particular, the levels of activated Akt (protein kinase B) and inactive glycogen synthase kinase-3β (i.e. a kinase that regulates the nuclear export and degradation of Cyclin D1) are reduced in MECs lacking Jak2. The proliferation of Jak2-deficient MECs can be rescued by expressing of a mutant form of Cyclin D1 that cannot be phosphorylated by glycogen synthase kinase-3β and therefore constitutively resides in the nucleus. Besides discriminating Jak2-dependent and Jak2-independent signaling events emerging from the PRLR, our observations provide a possible mechanism for phenotypic similarities between Cyclin D1 knockouts and females lacking individual members of the PRLR signaling cascade, in particular the PRLR, Jak2, and Stat5.

Original languageEnglish (US)
Pages (from-to)1877-1892
Number of pages16
JournalMolecular Endocrinology
Volume21
Issue number8
DOIs
StatePublished - Aug 3 2007

Fingerprint

Janus Kinase 2
Cyclin D1
Breast
Epithelial Cells
Prolactin Receptors
STAT5 Transcription Factor
Prolactin
Glycogen Synthase Kinase 3
Cell Nucleus Active Transport
Phosphotransferases
bcl-1 Genes
Focal Adhesion Protein-Tyrosine Kinases
Proto-Oncogene Proteins c-akt
Human Mammary Glands
Transducers
Transcriptional Activation
Phosphorylation

ASJC Scopus subject areas

  • Molecular Biology
  • Endocrinology

Cite this

The Janus kinase 2 is required for expression and nuclear accumulation of cyclin D1 in proliferating mammary epithelial cells. / Sakamoto, Kazuhito; Creamer, Bradley A.; Triplett, Aleata A.; Wagner, Kay Uwe.

In: Molecular Endocrinology, Vol. 21, No. 8, 03.08.2007, p. 1877-1892.

Research output: Contribution to journalArticle

Sakamoto, Kazuhito ; Creamer, Bradley A. ; Triplett, Aleata A. ; Wagner, Kay Uwe. / The Janus kinase 2 is required for expression and nuclear accumulation of cyclin D1 in proliferating mammary epithelial cells. In: Molecular Endocrinology. 2007 ; Vol. 21, No. 8. pp. 1877-1892.
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