title: Serotonin suppresses β-casein expression via PTP1B activation in human mammary epithelial cells.
abstract: Serotonin (5-hydroxytriptamine, 5-HT) has an important role in milk volume homeostasis within the mammary gland during lactation. We have previously shown that the expression of β-casein, a differentiation marker in mammary epithelial cells, is suppressed via 5-HT-mediated inhibition of signal transduction and activator of transcription 5 (STAT5) phosphorylation in the human mammary epithelial MCF-12A cell line. In addition, the reduction of β-casein in turn was associated with 5-HT7 receptor expression in the cells. The objective of this study was to determine the mechanisms underlying the 5-HT-mediated suppression of β-casein and STAT5 phosphorylation. The β-casein level and phosphorylated STAT5 (pSTAT5)/STAT5 ratio in the cells co-treated with 5-HT and a protein kinase A (PKA) inhibitor (KT5720) were significantly higher than those of cells treated with 5-HT alone. Exposure to 100 μM db-cAMP for 6 h significantly decreased the protein levels of β-casein and pSTAT5 and the pSTAT5/STAT5 ratio, and significantly increased PTP1B protein levels. In the cells co-treated with 5-HT and an extracellular signal-regulated kinase1/2 (ERK) inhibitor (FR180294) or Akt inhibitor (124005), the β-casein level and pSTAT5/STAT5 ratio were equal to those of cells treated with 5-HT alone. Treatment with 5-HT significantly induced PTP1B protein levels, whereas its increase was inhibited by KT5720. In addition, the PTP1B inhibitor sc-222227 increased the expression levels of β-casein and the pSTAT5/STAT5 ratio. Our observations indicate that PTP1B directly regulates STAT5 phosphorylation and that its activation via the cAMP/PKA pathway downstream of the 5-HT7 receptor is involved in the suppression of β-casein expression in MCF-12A cells.
authors.affiliation: Department of Clinical Pharmaceutics and Pharmacy Practice, School of Pharmacy, Iwate Medical University, Shiwagun, Iwate 028-3603, Japan. Electronic address: chibat@iwate-med.ac.jp.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Chiba
authors.affiliation: Department of Pharmacology, Nihon Pharmaceutical University, Ina-machi, Kitaadachi-gun, Saitama 362-0806, Japan.
authors.forename: Tomoji
authors.initials: T
authors.lastname: Maeda
authors.affiliation: Department of Pharmacotherapeutics, School of Pharmacy, Iwate Medical University, Shiwagun, Iwate 028-3603, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Sanbe
authors.affiliation: Department of Clinical Pharmaceutics and Pharmacy Practice, School of Pharmacy, Iwate Medical University, Shiwagun, Iwate 028-3603, Japan.
authors.forename: Kenzo
authors.initials: K
authors.lastname: Kudo
mesh_terms: D001940:Breast / Q000378:metabolism*; D002364:Caseins / Q000378:metabolism*; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000737:chemistry; D004847:Epithelial Cells / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D010766:Phosphorylation; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1 / Q000378:metabolism*; D011985:Receptors, Serotonin / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D002364:Caseins; D004791:Enzyme Inhibitors; D011985:Receptors, Serotonin; D050799:STAT5 Transcription Factor; C104425:serotonin 7 receptor; D012701:Serotonin; C516607:PTPN1 protein, human; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1
keywords: 5-HT(7) receptor; Human mammary gland; MCF-12A; Serotonin; β-casein