Nucling, a novel apoptosis-associated protein, controls mammary gland involution by regulating NF-κB and STAT3

Calpains, the proteases of two faces controlling the epithelial homeostasis in mammary gland

Calpain-1 and calpain-2 are calcium-dependent Cys-proteases ubiquitously expressed in mammalian tissues with a processive, rather than degradative activity. They are crucial for physiological mammary gland homeostasis as well as for breast cancer progression. A growing number of evidences indicate that their pleiotropic functions depend on the cell type, tissue and biological context where they are expressed or dysregulated. This review considers these standpoints to cover the paradoxical role of calpain-1 and -2 in the mammary tissue either, under the physiological conditions of the postlactational mammary gland regression or the pathological context of breast cancer. The role of both calpains will be examined and discussed in both conditions, followed by a brief snapshot on the present and future challenges for calpains, the two-gateway proteases towards tissue homeostasis or tumor development.

Early effects of lipoteichoic acid from Staphylococcus aureus on milk production-related signaling pathways in mouse mammary epithelial cells

Staphylococcus aureus causes subclinical mastitis; lipoteichoic acid (LTA) from S. aureus causes mastitis-like adverse effects on milk production by mammary epithelial cells (MECs). Here, we investigated the early effects of LTA from S. aureus on mouse MECs using a culture model, in which MECs produced milk components and formed less permeable tight junctions (TJs). In MECs of this model, Toll-like receptor 2 (receptor for LTA), was localized on the apical membrane, similar to MECs in lactating mammary glands. LTA weakened the TJ barrier within 1 h, concurrently with localization changes of claudin 4. LTA treatment for 24 h increased αS1-casein and decreased β-casein levels. In MECs exposed to LTA, the activation level of signal transducer and activator of transcription 5 (major transcriptional factor for milk production) was low. LTA activated signaling pathways related to cell survival (extracellular signal-regulated kinase, heat shock protein 27, and Akt) and inflammation (p38, c-Jun N-terminal kinase, and nuclear factor κB). Thus, LTA caused abnormalities in casein production and weakened the TJs by affecting multiple signaling pathways in MECs. LTA-induced changes in signaling pathways were not uniform in all MECs. Such complex and semi-negative actions of LTA may contribute to subclinical mastitis caused by S. aureus.

Suppressive effects of curcumin on milk production without inflammatory responses in lactating mammary epithelial cells

BACKGROUND

Curcumin is a naturally occurring polyphenol found in Curcuma longa with multiple therapeutic properties, such as anti-inflammatory, wound healing and anti-cancer effects. Curcuma longa is also used as a galactagogue to improve milk production during lactation.

PURPOSE

To assess curcumin could have therapeutic potential for breastfeeding mothers, we investigated whether and how curcumin influences milk production in lactating mammary epithelial cells (MECs) at the cellular and molecular levels.

METHODS

We prepared a lactating MEC culture model that produced milk components and formed less-permeable tight junctions (TJs) to investigate the molecular mechanism of curcumin on milk production, TJs, and inflammation in vitro.

RESULTS

Curcumin downregulated milk production in lactation MECs concurrently with inactivation of lactogenesis-relating signaling (STAT5 and glucocorticoid receptor). The maintenance of a less-permeable TJ barrier was also confirmed, although the TJ protein claudin-4 increased. Curcumin inactivated NFκB and STAT3 signaling, which are closely involved in inflammatory responses in weaning and mastitis mammary glands. The expression levels of IL-1β and TNF-α were also decreased by curcumin treatment. Furthermore, curcumin blocked activation of inflammatory signaling by lipopolysaccharide treatment in MECs, similar to those in MECs that were treated with diclofenac sodium. The drastic phosphorylation of ERK was induced by curcumin treatment in the absence of EGF. U0126, an inhibitor of ERK phosphorylation, attenuated the adverse effects of curcumin on lactating MECs.

CONCLUSION

The results of the present study suggests that curcumin downregulates milk production via inactivation of STAT5 and GR signaling with concurrent suppression of inflammatory responses via STAT3 and NFκB signaling in MECs. These findings provide new insights into the role of curcumin as a mild suppressor of milk production without inflammatory damages in breastfeeding mothers.

Intracellular partners of fibroblast growth factors 1 and 2 - implications for functions

Fibroblast growth factors 1 and 2 (FGF1 and FGF2) are mainly considered as ligands of surface receptors through which they regulate a broad spectrum of biological processes. They are secreted in non-canonical way and, unlike other growth factors, they are able to translocate from the endosome to the cell interior. These unique features, as well as the role of the intracellular pool of FGF1 and FGF2, are far from being fully understood. An increasing number of reports address this problem, focusing on the intracellular interactions of FGF1 and 2. Here, we summarize the current state of knowledge of the FGF1 and FGF2 binding partners inside the cell and the possible role of these interactions. The partner proteins are grouped according to their function, including proteins involved in secretion, cell signaling, nucleocytoplasmic transport, binding and processing of nucleic acids, ATP binding, and cytoskeleton assembly. An in-depth analysis of the network of these binding partners could indicate novel, non-classical functions of FGF1 and FGF2 and uncover an additional level of a fine control of the well-known FGF-regulated cellular processes.

Nicotine directly affects milk production in lactating mammary epithelial cells concurrently with inactivation of STAT5 and glucocorticoid receptor in vitro

Nicotine from tobacco smoke is absorbed into the bloodstream and transferred into breast milk in breastfeeding mothers. Smoking causes a decrease in breast milk volume, adverse changes to the milk composition, and a shortened lactation period. Breast milk is produced by mammary epithelial cells (MECs) in mammary glands during lactation. However, it remains unclear whether nicotine directly affects milk production in lactating MECs. To address this issue, we prepared a culture model with high milk production ability and less-permeable tight junctions (TJs) by seeding mouse MECs on a cell culture insert. Lactating MECs showed expression of α2, α3, β2, and β4 of nicotinic acetylcholine receptors. The high concentration of nicotine at 10-100 μM inhibited β-casein secretion and caused abnormal localization of TJ proteins. We subsequently investigated whether nicotine at a physiological concentration could affect lactating MECs. Nicotine at 1.0 μM directly inhibited α- and β-casein secretion in lactating MECs concurrently with inactivation of STAT5 and glucocorticoid receptor without affecting the TJ barrier. Nicotine treatment also induced MEC apoptosis concurrently with inactivation of Akt. These results support the adverse effects of nicotine on breastfeeding in smoking mothers.

Ankyrin repeat-containing N-Ank proteins shape cellular membranes

Cells of multicellular organisms need to adopt specific morphologies. However, the molecular mechanisms bringing about membrane topology changes are far from understood-mainly because knowledge of membrane-shaping proteins that can promote local membrane curvatures is still limited. Our analyses unveiled that several members of a large, previously unrecognised protein family, which we termed N-Ank proteins, use a combination of their ankyrin repeat array and an amino (N)-terminal amphipathic helix to bind and shape membranes. Consistently, functional analyses revealed that the N-Ank protein ankycorbin (NORPEG/RAI14), which was exemplarily characterised further, plays an important, ankyrin repeat-based and N-terminal amphipathic helix-dependent role in early morphogenesis of neurons. This function furthermore required coiled coil-mediated self-assembly and manifested as ankycorbin nanodomains marked by protrusive membrane topologies. In summary, here, we unveil a class of powerful membrane shapers and thereby assign mechanistic and cell biological functions to the N-Ank protein superfamily.

Knockdown of UACA inhibitsproliferation and invasion and promotes senescence of hepatocellular carcinoma cells

Uveal autoantigen with coiled-coil domains and ankyrin repeats (UACA/Nucling), has been reported to be upregulated in various cancers. However, its expression and function have not been studied in hepatocellular carcinoma (HCC). In the present study, expression of UACA was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and the results revealed that UACA was upregulated in 23 cases of HCC compared with paired corresponding non-tumor liver tissues. In addition, the upregulation of UACA in HCC was further validated by analyzing the datasets from The Cancer Genome Atlas-Liver Hepatocellular Carcinoma (TCGA-LIHC) and GSE36376. Furthermore, knockdown of UACA suppressed the proliferative and invasive ability as well as inducing senescence of HCC cells. Besides, the expression level of UACA was positively associated with Hif1α (hypoxia-inducible factor 1α) in HCC datasets from TCGA-LIHC and GSE54236. Moreover, treatment with CoCl2 led to the increased expression and the localization alteration of UACA in HCC cells. In summary, UACA is upregulated in HCC and knockdown of UACA ameliorated malignant behaviors of HCC cells, and UACA was correlated with and under control of Hif1α.