Nuclear Jak2 and Transcription Factor NF1-C2: a Novel Mechanism of Prolactin Signaling in Mammary Epithelial Cells

ABSTRACT The classical mechanism by which prolactin transduces its signal in mammary epithelial cells is by activation of cytosolic signal transducer and activator of transcription 5 (Stat5) via a plasma membrane-associated prolactin receptor-Janus kinase 2 (Jak2) complex. Here we describe an alternative pathway through which prolactin via Jak2 localized in the nucleus activates the transcription factor nuclear factor 1-C2 (NF1-C2). Previous reports have demonstrated a nuclear localization of Jak2, but the physiologic importance of nuclear Jak2 has not been clear. We demonstrate that nuclear Jak2 regulates the amount of active NF1-C2 through tyrosine phosphorylation and proteasomal degradation. Our data also demonstrate a link between prolactin and p53 as well as the milk gene carboxyl ester lipase through nuclear Jak2 and NF1-C2. Hence, we describe a novel pathway through which nuclear Jak2 is subject to regulation by prolactin in mammary epithelial cells.

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The ETS Transcription Factor ESE-1 Transforms MCF-12A Human Mammary Epithelial Cells via a Novel Cytoplasmic Mechanism

Molecular and Cellular Biology ◽

10.1128/mcb.24.12.5548-5564.2004 ◽

2004 ◽

Vol 24 (12) ◽

pp. 5548-5564 ◽

Cited By ~ 39

Author(s):

Jason D. Prescott ◽

Karen S. N. Koto ◽

Meenakshi Singh ◽

Arthur Gutierrez-Hartmann

Keyword(s):

Breast Cancer ◽

Transcription Factor ◽

Epithelial Cells ◽

Nuclear Localization ◽

Human Breast Cancer ◽

Mammary Epithelial Cells ◽

Cell Transformation ◽

Mammary Epithelial ◽

Human Breast ◽

Human Mammary Epithelial

ABSTRACT Several different transcription factors, including estrogen receptor, progesterone receptor, and ETS family members, have been implicated in human breast cancer, indicating that transcription factor-induced alterations in gene expression underlie mammary cell transformation. ESE-1 is an epithelium-specific ETS transcription factor that contains two distinguishing domains, a serine- and aspartic acid-rich (SAR) domain and an AT hook domain. ESE-1 is abundantly expressed in human breast cancer and trans-activates epithelium-specific gene promoters in transient transfection assays. While it has been presumed that ETS factors transform mammary epithelial cells via their nuclear transcriptional functions, here we show (i) that ESE-1 protein is cytoplasmic in human breast cancer cells; (ii) that stably expressed green fluorescent protein-ESE-1 transforms MCF-12A human mammary epithelial cells; and (iii) that the ESE-1 SAR domain, acting in the cytoplasm, is necessary and sufficient to mediate this transformation. Deletion of transcriptional regulatory or nuclear localization domains does not impair ESE-1-mediated transformation, whereas fusing the simian virus 40 T-antigen nuclear localization signal to various ESE-1 constructs, including the SAR domain alone, inhibits their transforming capacity. Finally, we show that the nuclear localization of ESE-1 protein induces apoptosis in nontransformed mammary epithelial cells via a transcription-dependent mechanism. Together, our studies reveal two distinct ESE-1 functions, apoptosis and transformation, where the ESE-1 transcription activation domain contributes to apoptosis and the SAR domain mediates transformation via a novel nonnuclear, nontranscriptional mechanism. These studies not only describe a unique ETS factor transformation mechanism but also establish a new paradigm for cell transformation in general.

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Prolactin receptor on dissociated mammary epithelial cells at different stages of development

Molecular and Cellular Endocrinology ◽

10.1016/0303-7207(78)90087-4 ◽

1978 ◽

Vol 12 (3) ◽

pp. 285-298 ◽

Cited By ~ 29

Author(s):

S. Sakai ◽

J. Enami ◽

S. Nandi ◽

M.R. Banerjee

Keyword(s):

Epithelial Cells ◽

Mammary Epithelial Cells ◽

Prolactin Receptor ◽

Mammary Epithelial ◽

Stages Of Development

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Transcription factor E2F4 is a positive regulator of milk biosynthesis and proliferation of bovine mammary epithelial cells

Cell Biology International ◽

10.1002/cbin.11225 ◽

2019 ◽

Vol 44 (1) ◽

pp. 229-241

Author(s):

Zhen Zhen ◽

Minghui Zhang ◽

Xiaohan Yuan ◽

Meng Li

Keyword(s):

Transcription Factor ◽

Epithelial Cells ◽

Mammary Epithelial Cells ◽

Mammary Epithelial ◽

Bovine Mammary Epithelial Cells ◽

Positive Regulator

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Dipeptide (Methionyl-Methionine) Transport and Its Effect on β-Casein Synthesis in Bovine Mammary Epithelial Cells

Cellular Physiology and Biochemistry ◽

10.1159/000492987 ◽

2018 ◽

Vol 49 (2) ◽

pp. 479-488 ◽

Cited By ~ 9

Author(s):

Caihong Wang ◽

Fengqi Zhao ◽

Jianxin Liu ◽

Hongyun Liu

Keyword(s):

Epithelial Cells ◽

Cell Viability ◽

Transport Properties ◽

Mammary Epithelial Cells ◽

Mammary Epithelial ◽

Janus Kinase ◽

Initiation Factor ◽

Peptide Transporter ◽

Small Interference Rna ◽

Bovine Mammary Epithelial Cells

Background/Aims: The aim of this study was to investigate the transport properties and utilization of methionyl-methionine dipeptide (Met-Met) in β-casein (β-CN) synthesis in bovine mammary epithelial cells (BMECs). Methods: The transport properties were studied for the effects of time, pH, concentration, temperature and inhibitors using Met-Met-FITC in BMECs. BMECs were treated with different concentrations of Met-Met (0, 20, 40, 80, 120 and 160 µg/ml). In several experiments, the cells were treated with Janus kinase 2 (JAK2) inhibitor (tyrphostin AG-490, 50 µM) and mammalian target of rapamycin (mTOR) inhibitor (rapamycin, 100 ng/ml). Results: The uptake of Met-Met-FITC by BMECs was rapid during the first fifteen minutes and became saturated after 15 minutes. The transport of Met-Met-FITC in BMECs exhibited a Michaelis constant of 52.4 µM and maximum transport velocity of 14.8 pmol/min/mg protein. The uptake of Met-Met-FITC in BMECs was pH-dependent, peaked at pH 6.5 and was significantly inhibited by other peptides, including Met-Lys, Lys-Lys, Gly-Met, Gly-Leu and Met-Leu. Knocking down the peptide transporter 2 (PepT2) with small interference RNA markedly decreased Met-Met-FITC uptake. Met-Met concentration-dependently increased the PepT2 expression and β-CN synthesis in BMECs with an optimal concentration of 80 µg/ml. At 80 µg/ml, Met-Met also enhanced the cell viability and cyclin D1 expression and promoted cell cycle transition from G1 phase to S phase. In addition, 80 µg/ml Met-Met increased the mRNA abundance of JAK2 and signal transducer and activator of transcription 5 (STAT5) and enhanced the phosphorylation of JAK2, STAT5, mTOR, p70 ribosomal S6 kinase 1 and eukaryotic initiation factor 4E binding protein 1. The inhibition of JAK2 and mTOR significantly decreased Met-Met-induced increase in cell viability and β-CN synthesis in BMECs. Conclusion: Our data elucidated the properties of peptide transporter and its effect on β-CN synthesis in BMECs. Met-Met, taken up by PepT2, enhances cell proliferation and promotes β-CN synthesis by activating JAK2-STAT5 and mTOR signaling pathways in BMECs.

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