Stat5a increases lactation of dairy cow mammary gland epithelial cells cultured in vitro

PAX6 promotes neuroendocrine phenotypes of prostate cancer via enhancing MET/STAT5A-mediated chromatin accessibility

BACKGROUND

Neuroendocrine prostate cancer (NEPC) is a lethal subset of prostate cancer which is characterized by neuroendocrine differentiation and loss of androgen receptor (AR) signaling. Growing evidence reveals that cell lineage plasticity is crucial in the failure of NEPC therapies. Although studies suggest the involvement of the neural transcription factor PAX6 in drug resistance, its specific role in NEPC remains unclear.

METHODS

The expression of PAX6 in NEPC was identified via bioinformatics and immunohistochemistry. CCK8 assay, colony formation assay, tumorsphere formation assay and apoptosis assay were used to illustrate the key role of PAX6 in the progression of in vitro. ChIP and Dual-luciferase reporter assays were conducted to confirm the binding sequences of AR in the promoter region of PAX6, as well as the binding sequences of PAX6 in the promoter regions of STAT5A and MET. For in vivo validation, the xenograft model representing NEPC subtype underwent pathological analysis to verify the significant role of PAX6 in disease progression. Complementary diagnoses were established through public clinical datasets and transcriptome sequencing of specific cell lines. ATAC-seq was used to detect the chromatin accessibility of specific cell lines.

RESULTS

PAX6 expression was significantly elevated in NEPC and negatively regulated by AR signaling. Activation of PAX6 in non-NEPC cells led to NE trans-differentiation, while knock-down of PAX6 in NEPC cells inhibited the development and progression of NEPC. Importantly, loss of AR resulted in an enhanced expression of PAX6, which reprogramed the lineage plasticity of prostate cancer cells to develop NE phenotypes through the MET/STAT5A signaling pathway. Through ATAC-seq, we found that a high expression level of PAX6 elicited enhanced chromatin accessibility, mainly through attenuation of H4K20me3, which typically causes chromatin silence in cancer cells.

CONCLUSION

This study reveals a novel neural transcription factor PAX6 could drive NEPC progression and suggest that it might serve as a potential therapeutic target for the management of NEPC.

Molecular Characteristics of JAK2 and Its Effect on the Milk Fat and Casein Synthesis of Ovine Mammary Epithelial Cells

In addition to its association with milk protein synthesis via the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway, JAK2 also affects milk fat synthesis. However, to date, there have been no reports on the effect of JAK2 on ovine mammary epithelial cells (OMECs), which directly determine milk yield and milk contents. In this study, the coding sequence (CDS) region of ovine JAK2 was cloned and identified and its tissue expression and localization in ovine mammary glands, as well as its effects on the viability, proliferation, and milk fat and casein levels of OMECs, were also investigated. The CDS region of ovine JAK2, 3399 bp in length, was cloned and its authenticity was validated by analyzing its sequence similarity with JAK2 sequences from other animal species using a phylogenetic tree. JAK2 was found to be expressed in six ovine tissues, with the highest expression being in the mammary gland. Over-expressed JAK2 and three groups of JAK2 interference sequences were successfully transfected into OMECs identified by immunofluorescence staining. When compared with the negative control (NC) group, the viability of OMECs was increased by 90.1% in the pcDNA3.1-JAK2 group. The over-expression of JAK2 also increased the number and ratio of EdU-labeled positive OMECs, as well as the expression levels of three cell proliferation marker genes. These findings show that JAK2 promotes the viability and proliferation of OMECs. Meanwhile, the triglyceride content in the over-expressed JAK2 group was 2.9-fold higher than the controls and the expression levels of four milk fat synthesis marker genes were also increased. These results indicate that JAK2 promotes milk fat synthesis. Over-expressed JAK2 significantly up-regulated the expression levels of casein alpha s2 (CSN1S2), casein beta (CSN2), and casein kappa (CSN3) but down-regulated casein alpha s1 (CSN1S1) expression. In contrast, small interfered JAK2 had the opposite effect to JAK2 over-expression on the viability, proliferation, and milk fat and milk protein synthesis of OMECs. In summary, these results demonstrate that JAK2 promotes the viability, proliferation, and milk fat synthesis of OMECs in addition to regulating casein expression in these cells. This study contributes to a better comprehension of the role of JAK2 in the lactation performance of sheep.

Molecular mechanisms in the miR-33a/LPPR4 pathway regulating unsaturated fatty acid synthesis in bovine mammary epithelial cells

The regulatory mechanisms governing metabolism of fatty acids in cow mammary gland are crucial for establishing relationships between milk quality and fatty acid content. Both, microRNAs (miRNAs) and protein-coding genes are important factors involved in the regulation of milk fat synthesis. In this study, high-throughput sequencing of miRNAs and mRNAs in bovine mammary gland tissue was performed during peak lactation (3 samples) and late lactation (3 samples) periods to characterize expression profiles. Differential expression (DE) analyses of miRNA and mRNA and miRNA-mRNA regulatory pathway screening were performed. Two-hundred eighty regulatory miRNA-mRNA pairs were identified, including the miR-33a-lipid phosphate phosphatase-related protein type 4 (LPPR4) pathway. Bioinformatics prediction, dual-luciferase reporter system detection, qRT-PCR, and Western blotting revealed that miR-33a can directly target LPPR4 and inhibit its expression. Experiments also revealed that miR-33a promotes the synthesis of triglycerides and increases the content of unsaturated fatty acids (UFAs) in bovine mammary epithelial cells (BMECs). These results indicate that miR-33a via LPPR4 plays an important role in the regulation of milk fat synthesis and UFA levels.

Role of the JAK-STAT Pathway in Bovine Mastitis and Milk Production

Simple Summary

The cytokine-activated Janus kinase (JAK)—signal transducer and activator of transcription (STAT) pathway has an important role in the regulation of immunity and inflammation. In addition, the signaling of this pathway has been reported to be associated with mammary gland development and milk production. Because of such important functions, the JAK-STAT pathway has been widely targeted in both human and animal diseases as a therapeutic agent. Recently, the JAK2, STATs, and inhibitors of the JAK-STAT pathway, especially cytokine signaling suppressors (SOCSs), have been reported to be associated with milk production and mastitis-resistance phenotypic traits in dairy cattle. Thus, in the current review, we attempt to overview the development of the JAK-STAT pathway role in bovine mastitis and milk production.

Abstract

The cytokine-activated Janus kinase (JAK)—signal transducer and activator of transcription (STAT) pathway is a sequence of communications between proteins in a cell, and it is associated with various processes such as cell division, apoptosis, mammary gland development, lactation, anti-inflammation, and immunity. The pathway is involved in transferring information from receptors on the cell surface to the cell nucleus, resulting in the regulation of genes through transcription. The Janus kinase 2 (JAK2), signal transducer and activator of transcription A and B (STAT5 A & B), STAT1, and cytokine signaling suppressor 3 (SOCS3) are the key members of the JAK-STAT pathway. Interestingly, prolactin (Prl) also uses the JAK-STAT pathway to regulate milk production traits in dairy cattle. The activation of JAK2 and STATs genes has a critical role in milk production and mastitis resistance. The upregulation of SOCS3 in bovine mammary epithelial cells inhibits the activation of JAK2 and STATs genes, which promotes mastitis development and reduces the lactational performance of dairy cattle. In the current review, we highlight the recent development in the knowledge of JAK-STAT, which will enhance our ability to devise therapeutic strategies for bovine mastitis control. Furthermore, the review also explores the role of the JAK-STAT pathway in the regulation of milk production in dairy cattle.

Single-step genome-wide association for longitudinal traits of Canadian Ayrshire, Holstein, and Jersey dairy cattle

Estimating single nucleotide polymorphism (SNP) effects over time is essential to identify and validate candidate genes (or quantitative trait loci) associated with time-dependent variation of economically important traits and to better understand the underlying mechanisms of lactation biology. Therefore, in this study, we aimed to estimate time-dependent effects of SNP and identifying candidate genes associated with milk (MY), fat (FY), and protein (PY) yields, and somatic cell score (SCS) in the first 3 lactations of Canadian Ayrshire, Holstein, and Jersey breeds, as well as suggest their potential pattern of phenotypic effect over time. Random regression coefficients for the additive direct genetic effect were estimated for each animal using single-step genomic BLUP, based on 2 random regression models: one considering MY, FY, and PY in the first 3 lactations and the other considering SCS in the first 3 lactations. Thereafter, SNP solutions were obtained for random regression coefficients, which were used to estimate the SNP effects over time (from 5 to 305 d in lactation). The top 1% of SNP that showed a high magnitude of SNP effect in at least 1 d in lactation were selected as relevant SNP for further analyses of candidate genes, and clustered according to the trajectory of their SNP effects over time. The majority of SNP selected for MY, FY, and PY increased the magnitude of their effects over time, for all breeds. In contrast, for SCS, most selected SNP decreased the magnitude of their effects over time, especially for the Holstein and Jersey breeds. In general, we identified a different set of candidate genes for each breed, and similar genes were found across different lactations for the same trait in the same breed. For some of the candidate genes, the suggested pattern of phenotypic effect changed among lactations. Among the lactations, candidate genes (and their suggested phenotypic effect over time) identified for the second and third lactations were more similar to each other than for the first lactation. Well-known candidate genes with major effects on milk production traits presented different suggested patterns of phenotypic effect across breeds, traits, and lactations in which they were identified. The candidate genes identified in this study can be used as target genes in studies of gene expression.

Leucine Promotes Milk Synthesis in Bovine Mammary Epithelial Cells via the PI3K-DDX59 Signaling

Leucine is an essential amino acid in the milk production of bovine mammary glands, but the regulatory roles and molecular mechanisms of leucine are still not known well. This study investigated the roles of leucine on milk synthesis and explored the corresponding mechanism in bovine mammary epithelial cells (BMECs). Leucine (0, 0.25, 0.5, 0.75, 1.0, and 1.25 mM) was added to BMECs that were cultured in FBS-free OPTI-MEM medium. Leucine significantly promoted milk protein and milk fat synthesis and also increased phosphorylation of mTOR signaling protein and the protein expression levels of SREBP-1c, with the most significant effects at 0.75 mM concentration. Leucine increased the expression and nuclear localization of DDX59, and loss and gain of gene function experiments further reveal that DDX59 mediates the stimulation of leucine on the mRNA expression variation of mTOR and SREBP-1c genes. PI3K inhibition experiment further detected that leucine upregulated expression of DDX59 and its downstream signaling via PI3K activation. ChIP-qPCR analysis further proved the binding of DDX59 to the promoter regions of mTOR and SREBP-1c. In summary, these data prove that DDX59 positively regulates the mTOR and SREBP-1c signaling pathways leading to synthesis of milk, and leucine regulates these two signaling pathways through the PI3K-DDX59 signaling.

Effect of interaction between leucine and acetate on the milk protein synthesis in bovine mammary epithelial cells

The interaction between Leucine (Leu) and acetate affecting milk protein synthesis in the bovine mammary epithelial cells (BMECs), and underlying the molecular mechanisms are not well understood. The objectives of this study were to investigate the effect of Leu, acetate, and their interaction on the expression of genes involved in milk protein synthesis, and JACK2/STAT5, mTOR and AMP-activated protein kinase (AMPK) signaling pathway. The study was a 2 × 6 factorial arrangement with treatments: Leu concentration (0.45 and 1.8 mM) and acetate concentration (0, 4, 6, 8, 10, and 12 mM). The results showed that 1.8 mM Leu or 8-10 mM acetate had positive effect on ATP content, the expression of casein genes, JACK2/STAT5 and phosphorylation of mTOR pathway, but reduced AMPK phosphorylation. Leu at 1.8mM had a positive effect on the up-regulation of acetate on ATP content, the expression of CSN1S1, CSN2, CSN3, and JACK2, the expression and phosphorylation of eukaryotic initiation factor 4E, p70 ribosomal protein S6 kinase-1, and mTOR, but reducing AMPK phosphorylation. The results suggest that acetate, Leu, and their interaction have effect on milk protein synthesis through the JACK2/STAT5, mTOR, and AMPK pathway. Acetate addition up-regulated the effect of Leu on milk protein synthesis, and Leu facilitated the up-regulation of acetate on milk protein synthesis through these pathways.

MEN1/Menin regulates milk protein synthesis through mTOR signaling in mammary epithelial cells

The MEN1 gene, which encodes the protein Menin, was investigated for its regulatory role in milk protein synthesis in mammary glands. Menin responds to nutrient and hormone levels via the PI3K/Akt/mTOR pathway. Bovine mammary epithelial cells and tissues were used as experimental models in this study. The results revealed that the milk protein synthesis capacity of mammary epithelial cells could be regulated by MEN1/Menin. The overexpression of Menin caused significant suppression of factors involved in the mTOR pathway, as well as milk protein κ-casein (CSNK). In contrast, a significant increase in these factors and CSNK was observed upon MEN1/Menin knockdown. The repression of MEN1/Menin on the mTOR pathway was also observed in mammary gland tissues. Additionally, MEN1/Menin was found to elicit a negative response on prolactin (PRL) and/or insulin (INS), which caused a similar downstream impact on mTOR pathway factors and milk proteins. Collectively, our data indicate that MEN1/Menin could play a regulatory role in milk protein synthesis through mTOR signaling in the mammary gland by mediating the effects of hormones and nutrient status. The discovery of Menin's role in mammary glands suggests Menin could be potential new target for the improvement of milk performance and adjustment of lactation period of dairy cows.

Establishment of a 3D cell culture model of primary bovine mammary epithelial cells extracted from fresh milk

For the investigation of molecular processes underlying diseases of the bovine mammary gland, primary bovine mammary epithelial cells (pbMEC) are used. They are known to contribute to the innate immune system of the bovine mammary gland. The functionality of pbMEC depends on the maintenance of in vivo characteristics. So far, the optimization of pbMEC culture conditions was intended in a variety of experiments. For this purpose, most of the studies used stable cell lines or primary cells obtained from udder biopsies of slaughtered animals. By contrast, within our study, pbMEC of healthy and first lactating Brown Swiss cows were non-invasively isolated from fresh milk. The non-invasively isolated pbMEC were cultivated on the extracellular matrix-like scaffold Matrigel®_. Further, they were challenged with different compositions of proliferation media, containing lactogenic hormones and/or the essential amino acid L-lysine. Changes in expression levels of genes coding for milk proteins and for components of the janus kinase/signal transducers and activators of transcription (JAK-STAT) and mTOR pathways were analyzed by RT-qPCR. The secreted proteins were analyzed by LC-MS/MS measurements. We showed for the first time the establishment of a physiologically functional 3D cell culture model of pbMEC isolated from fresh milk. This represents a primary cell culture model system, based on non-invasive cell collection, that can be used to unravel physiological processes in an unbiased manner.

In vitro characterization and endocrine regulation of cholesterol and phospholipid transport in the mammary gland

Cell-based studies previously showed that the ATP-binding cassette transporter A1 (ABCA1) transfers cholesterol across mammary epithelial cells (MEC). Data for phospholipid transport are lacking, and it is unclear from which cellular source the transported cholesterol stems, whether this transport activates signaling pathways, and how lactogenic hormones regulate it. To clarify these aspects, lipid transport and expressional analyses were performed in bovine primary (bMEC) and/or immortalized (MAC-T) MEC cultures. Lipid efflux and ABCA1, ABCG1 and liver X receptorα mRNA levels were higher in MAC-T than bMEC. In MAC-T, the transported cholesterol originated mainly from the plasma membrane. ABCA1 dependent cholesterol efflux was higher than phosphatidylcholine efflux, was suppressed by probucol (ABCA1 inhibitor), AG490 (janus kinase-2 inhibitor), PD98059 (mitogen activated protein kinase kinase inhibitor) and pretreatment with β-cyclodextrin (lowering membrane cholesterol). Insulin was the only hormone significantly increasing cholesterol efflux. In conclusion, this study gives novel mechanistic and regulatory insights into the transport of cholesterol and phospholipids in MEC.

Alpha-ketoglutarate enhances milk protein synthesis by porcine mammary epithelial cells

Alpha-ketoglutarate (AKG), a key intermediate in the Krebs cycle, has been reported to promote protein synthesis through activating mechanistic targeting of rapamycin (mTOR) in enterocytes. The study tested the hypothesis that AKG may enhance growth and milk protein synthesis in porcine mammary epithelial cells (PMECs). PMECs were cultured for 96 h in Dulbecco's modified Eagle's-F12 Ham medium (DMEM-F12) containing prolactin (2 µg/ml) and AKG (0 or 1.5 mM). At the end of 96-h culture, the abundance of apoptosis-related proteins (caspase-3, caspase-9), milk-specific proteins (α-lactalbumin and β-casein), mTOR signaling proteins (mTOR, p-mTOR, PERK, p-PERK, eIF2a, P70S6K and p-P70S6K), and endoplasmic reticulum stress (ERS)-associated proteins (BiP and CHOP) in PMEC were determined. Addition of AKG dose-dependently enhanced cell viability in the absence or presence of prolactin, with optimal concentrations of AKG being at 1.0 and 1.5 mM, respectively. In the presence of prolactin, addition of 1.5 mM AKG: (1) decreased (P < 0.05) the abundance of caspase-3 and caspase-9 by 21 and 39 %; (2) enhanced (P < 0.05) the phosphorylation of p-mTOR and p-P70S6K by 39 and 89 %, respectively; (3) increased (P < 0.05) the production of β-casein and α-lactalbumin by 16 and 20 %, respectively; (4) attenuated (P < 0.05) the expression of CHOP by 34 % but promoted (P < 0.05) the expression of BiP by 46 %; (5) increased (P < 0.05) the secretion of lactose by 15 %, when compared to the 0 mM AKG group. Rapamycin (50 nM; an inhibitor of mTOR) attenuated (P < 0.05) the stimulatory effect of AKG on mTOR signaling and syntheses of milk protein and lactose, while relieving (P < 0.05) an inhibitory effect of AKG on expression of proteins related to ERS. Collectively, our results indicate that AKG enhances milk protein production by modulating mTOR and ERS signaling pathways in PMECs.

Pten regulates development and lactation in the mammary glands of dairy cows

Pten is a tumor suppressor gene regulating many cellular processes, including growth, adhesion, and apoptosis. In the aim of investigating the role of Pten during mammary gland development and lactation of dairy cows, we analyzed Pten expression levels in the mammary glands of dairy cows by using western blotting, immunohistochemistry, and quantitative polymerase chain reaction (qPCR) assays. Dairy cow mammary epithelial cells (DCMECs) were used to study the function of Pten in vitro. We determined concentrations of β-casein, triglyceride, and lactose in the culture medium following Pten overexpression and siRNA inhibition. To determine whether Pten affected DCMEC viability and proliferation, cells were analyzed by CASY-TT and flow cytometry. Genes involved in lactation-related signaling pathways were detected. Pten expression was also assessed by adding prolactin and glucose to cell cultures. When Pten was overexpressed, proliferation of DCMECs and concentrations for β-casein, triglyceride, and lactose were significantly decreased. Overexpression of Pten down-regulated expression of MAPK, CYCLIN D1, AKT, MTOR, S6K1, STAT5, SREBP1, PPARγ, PRLR, and GLUT1, but up-regulated 4EBP1 in DCMECs. The Pten siRNA inhibition experiments revealed results that opposed those from the gene overexpression experiments. Introduction of prolactin (PRL) increased secretion of β-casein, triglyceride, and lactose, but decreased Pten expression levels. Introduction of glucose also increased β-casein and triglyceride concentrations, but did not significantly alter Pten expression levels. The Pten mRNA and protein expression levels were decreased 0.3- and 0.4-fold in mammary glands of lactating cows producing high quality milk (milk protein >3.0%, milk fat >3.5%), compared with those cows producing low quality milk (milk protein <3.0%, milk fat <3.5%). In conclusion, Pten functions as an inhibitor during mammary gland development and lactation in dairy cows. It can down-regulate DCMECs secretion of β-casein, triglyceride, and lactose, and plays a critical role in lactation related signaling pathways.

MicroRNA-152 regulates DNA methyltransferase 1 and is involved in the development and lactation of mammary glands in dairy cows

MicroRNAs (miRNAs) are a class of small non-coding, endogenous regulatory RNAs that function by controlling gene expression at the post-transcriptional level. Using small RNA sequencing and qRT-PCR techniques, we found that the expression of miR-152 was significantly increased during lactation in the mammary glands of dairy cows producing high quality milk compared with that in cows producing low quality milk. Furthermore, DNA methyltransferase 1 (DNMT1), which is a target of miR-152, was inversely correlated with the expression levels of miR-152 in the mammary glands of dairy cows. Dairy cow mammary epithelial cells (DCMECs) were used as in vitro cell models to study the function of miR-152. The forced expression of miR-152 in DCMECs resulted in a marked reduction of DNMT1 at both mRNA and protein levels. This in turn led to a decrease in global DNA methylation and increased the expression of two lactation-related genes, serine/threonine protein kinase Akt (Akt) and peroxisome proliferator-activated receptor gamma (Pparγ). In contrast, inhibition of miR-152 showed the opposite results. By using an electronic Coulter counter (CASY-TT) and flow cytometer, we discovered that miR-152 enhanced the viability and multiplication capacity of DCMECs. In conclusion, miR-152 plays an important role in the development and lactation processes in the mammary glands of dairy cows. Our data provide insights into dairy cow mammary gland development and lactation.

Proteomic and functional analyses reveal MAPK1 regulates milk protein synthesis

L-Lysine (L-Lys) is an essential amino acid that plays fundamental roles in protein synthesis. Many nuclear phosphorylated proteins such as Stat5 and mTOR regulate milk protein synthesis. However, the details of milk protein synthesis control at the transcript and translational levels are not well known. In this current study, a two-dimensional gel electrophoresis (2-DE)/MS-based proteomic technology was used to identify phosphoproteins responsible for milk protein synthesis in dairy cow mammary epithelial cells (DCMECs). The effect of L-Lys on DCMECs was analyzed by CASY technology and reversed phase high performance liquid chromatography (RP-HPLC). The results showed that cell proliferation ability and β-casein expression were enhanced in DCMECs treated with L-Lys. By phosphoproteomics analysis, six proteins, including MAPK1, were identified up-expressed in DCMECs treated with 1.2 mM L-Lys for 24 h, and were verified by quantitative real-time PCR (qRT-PCR) and western blot. Overexpression and siRNA inhibition of MAPK1 experiments showed that MAPK1 upregulated milk protein synthesis through Stat5 and mTOR pathway. These findings that MAPK1 involves in regulation of milk synthesis shed new insights for understanding the mechanisms of milk protein synthesis.