IFN‐γ regulation of vacuolar pH, cathepsin D processing and autophagy in mammary epithelial cells
ABSTRACT In this study we examined the ability of interferon-γ (IFN-γ) to regulate mammary epithelial cell growth and gene expression, with particular emphasis on two genes: Maspin (a member of serine protease inhibitor superfamily), and the lysosomal aspartyl endopeptidase cathepsin D (CatD). The protein products of these genes are critically involved in regulation of multitude of biological functions in different stages of mammary tissue development and remodeling. In addition, the expression of Maspin is down-regulated in primary breast cancer and is lost in metastatic disease, while CatD is excessively produced and aberrantly secreted by breast cancer cells. We report that IFN-γ receptors are expressed in mammary epithelial cells, and receptor engagement by IFN-γ transduces the IFN-γ signal via Stat-1 resulting in decreased vacuolar pH. This change in vacuolar pH alters CatD protein processing and secretion concurrent with increased Maspin secretion. In addition, IFN-γ exerts a suppressive effect on cell growth and proliferation, and induces morphological changes in mammary epithelial cells. Our studies also reveal that breast cancer cells, which are devoid of Maspin, are refractory to IFN-γ with respect to changes in vacuolar pH and CatD. However, Maspin transfection of breast cancer cells partially sensitizes the cells to IFN-γ's effect, thus providing new therapeutic implications. J. Cell. Biochem. 105: 208–218, 2008. © 2008 Wiley-Liss, Inc.
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Article: IFN‐γ regulation of vacuolar pH, cathepsin D processing and autophagy in mammary epithelial cells
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ABSTRACT: Previous studies have indicated that adiponectin (APN) protects against cardiac remodeling, but the underlying mechanism remains unclear. The present study aimed to elucidate how APN regulates inflammatory responses and cardiac fibrosis in response to angiotensin II (Ang II). Male APN-knockout (APN KO) mice and wild type (WT) C57BL/6 littermates were subcutaneously infused with Ang II at 750 ng/kg per minute. Seven days after Ang II infusion, both APN KO and WT mice developed equally high blood pressure levels. However, APN KO mice developed more severe cardiac fibrosis and inflammation compared to WT mice. This finding was demonstrated by the upregulation of collagen I, α-smooth muscle actin, IL-1β, and TNF-α and increased macrophage infiltration in APN KO mice. Moreover, there were substantially fewer LC3-positive autophagosomes in macrophages in the hearts of Ang II-infused APN KO mice. Additional in vitro studies also revealed that globular APN treatment induced autophagy, inhibited Ang II-induced nuclear factor-κB activity and enhanced the expression of anti-inflammatory cytokines, including IL-10, Mgl-2, Fizzl, and Arg-1, in macrophages. In contrast, APN-induced autophagy and anti-inflammatory cytokine expression was diminished in Atg5-knockdown macrophages or by Compound C, an inhibitor of AMP-activated protein kinase (AMPK). Our study indicates that APN activates macrophage autophagy through the AMPK pathway and suppresses Ang II-induced inflammatory responses, thereby to reducing the extent of cardiac fibrosis.Endocrinology 03/2014; 155(6):en20132011. DOI:10.1210/en.2013-2011 · 4.64 Impact Factor
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ABSTRACT: Since its discovery as a lysosomal hydrolase, Cathepsin D (CatD) has been the subject of intensive scrutiny by numerous scientists. Those accumulated efforts have defined its biosynthetic pathway, structure, and companion proteins in the context of its perceived "house keeping" function. However, in the past two decades CatD has emerged as a multifunctional enzyme, involved in myriad biological processes beyond its original "housekeeping" role. CatD is responsible for selective and limited cleavage (quite distinct from non-specific protein degradation) of particular substrates vital to proper cellular function. These proteolytic events are critical in the control of biological processes, including cell cycle progression, differentiation and migration, morphogenesis and tissue remodeling, immunological processes, ovulation, fertilization, neuronal outgrowth, angiogenesis, and apoptosis. Consistent with the biological relevance of CatD, its deficiency, altered regulation or post-translational modification underlie important pathological conditions such as cancer, atherosclerosis, neurological and skin disorders. Specifically, deregulated synthesis, post-translational modifications and hyper-secretion of CatD, along with its mitogenic effects, are established hallmarks of cancer. More importantly, but less studied, is its significance in regulating the sensitivity to anticancer drugs. This review outlines CatD's post-translational modifications, cellular trafficking, secretion and protein binding partners in normal mammary gland, and restates the "site-specific" function of CatD which is most probably dictated by its post-translational modifications and binding partners. Noteworthy, CatD's association with one of its binding partners in the context of drug sensitivity is highlighted, with the optimism that it could contribute to the development of more effective chemotherapeutic agent(s) tailored for individual patients.
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ABSTRACT: The significant role of the embryonic morphogen Nodal in maintaining the pluripotency of embryonic stem cells is well documented. Interestingly, the recent discovery of Nodal's re-expression in several aggressive and metastatic cancers has highlighted its critical role in self renewal and maintenance of the stem cell-like characteristics of tumor cells, such as melanoma. However, the key TGFβ/Nodal signaling component(s) governing Nodal's effects in metastatic melanoma remain mostly unknown. By employing receptor profiling at the mRNA and protein level(s), we made the novel discovery that embryonic stem cells and metastatic melanoma cells share a similar repertoire of Type I serine/threonine kinase receptors, but diverge in their Type II receptor expression. Ligand:receptor crosslinking and native gel binding assays indicate that metastatic melanoma cells employ the heterodimeric TGFβ receptor I/TGFβ receptor II (TGFβRI/TGFβRII) for signal transduction, whereas embryonic stem cells use the Activin receptors I and II (ACTRI/ACTRII). This unexpected receptor usage by tumor cells was tested by: neutralizing antibody to block its function; and transfecting the dominant negative receptor to compete with the endogenous receptor for ligand binding. Furthermore, a direct biological role for TGFβRII was found to underlie vasculogenic mimicry (VM), an endothelial phenotype contributing to vascular perfusion and associated with the functional plasticity of aggressive melanoma. Collectively, these findings reveal the divergence in Nodal signaling between embryonic stem cells and metastatic melanoma that can impact new therapeutic strategies targeting the re-emergence of embryonic pathways. © 2014 Wiley Periodicals, Inc.International Journal of Cancer 10/2014; DOI:10.1002/ijc.29198 · 5.01 Impact Factor