Hepatocyte growth factor-regulated tyrosine kinase substrate (HRS) interacts with PELP1 and activates MAPK

Potential mechanism prediction of indole-3-propionic acid against diminished ovarian reserve via network pharmacology, molecular docking and experimental verification

BACKGROUND

Oxidative stress (OS) is one of the major causes of ovarian aging and dysfunction. Indole-3-propionic acid (IPA) is an indole compound derived from tryptophan with free radical scavenging and antioxidant properties, and thus may have potential applications in protecting ovarian function, although the exact mechanisms are unknown. This study aims to preliminarily elucidate the potential mechanisms of IPA that benefit ovarian reserve function through network pharmacology, molecular docking, and experimental verification.

METHODS

The related protein targets of IPA were searched on SwissTargetPrediction, TargetNet, BATMAN-TCM, and PharmMapper databases. The potential targets of diminished ovarian reserve (DOR) were identified from OMIM, GeneCards, DrugBank, and DisGeNET databases. The common targets were uploaded directly to the STRING database to construct PPI networks. We then performed GO and KEGG enrichment analysis on the targets. Subsequently, molecular docking and molecular dynamics simulation were used to validate the binding conformation of IPA to candidate targets. Furthermore, we carried out in vitro experiments to validate the prediction results of network pharmacology.

RESULTS

We identified a total of 61 potential targets for the interaction of IPA with DOR. The PPI network topological parameter analysis yielded 13 hub genes for DOR treatment. The GO biological process enrichment analysis identified 293 entries, mainly enriched in aging, signal transduction, response to hypoxia, negative regulation of apoptotic process, and positive regulation of cell proliferation. The KEGG enrichment analysis mainly included lipid and atherosclerosis, progesterone-mediated oocyte maturation, AGE-RAGE, relaxin, estrogen, and other signaling pathways. The molecular docking further revealed the direct binding of IPA with six hub proteins including NOS3, AKT1, EGFR, PPARA, SRC, and TNF. In vitro experiments showed that IPA pretreatment attenuated H2O2-induced cellular oxidative stress damage, while IPA exerted cytoprotective and antioxidant damage effects by regulating the six hub genes and antioxidant proteins.

CONCLUSION

We systematically illustrated the potential protective effects of IPA against DOR through multiple targets and pathways using network pharmacology, and further verified the cytoprotective effect and antioxidant properties of IPA through in vitro experiments. These findings provide new insights into the targets and molecular mechanisms whereby IPA improves DOR.

Role of the Intermediate Filament Protein Peripherin in Health and Disease

Intermediate filaments are the most heterogeneous class among cytoskeletal elements. While some of them have been well-characterized, little is known about peripherin. Peripherin is a class III intermediate filament protein with a specific expression in the peripheral nervous system. Epigenetic modifications are involved in this cell-type-specific expression. Peripherin has important roles in neurite outgrowth and stability, axonal transport, and axonal myelination. Moreover, peripherin interacts with proteins involved in vesicular trafficking, signal transduction, DNA/RNA processing, protein folding, and mitochondrial metabolism, suggesting a role in all these processes. This review collects information regarding peripherin gene regulation, post-translational modifications, and functions and its involvement in the onset of a number of diseases.

PELP1 is overexpressed in lung cancer and promotes tumor cell malignancy and resistance to tyrosine kinase inhibitor drug

Proline, glutamate, and leucine-rich protein 1 (PELP1) are involved in several cancers, but little is known about PELP1 in lung cancer. In this study, PELP1 expression was evaluated in 305 lung cancer (NSCLC) specimens to explore the role of PELP1 in lung cancer. After silencing PELP1, the proliferation, migration, invasion of tumor cells, PELP1 in relation to cell cycle and signaling pathways were evaluated, and whole-genome exons were analyzed. PELP1 is overexpressed in lung cancer, PELP1 expression correlated with squamous carcinoma, smoking, and wild-type EGFR status (all Ps<0.001) but associated with lung cancer-specific survival (P > 0.05). Silencing significantly inhibited lung cancer cell proliferation, migration, and invasion (P < 0.05) and promoted high sensitivity of lung cancer cells to tyrosine kinase inhibitor (TKI) gefitinib. PELP1-silenced cells showed downregulated phosphorylated MAPK, cyclinD1, CDK2, and upregulated RB (P < 0.05) but no change in AKT. In PELP1-silenced lung cancer cells, 140 genes were upregulated, and 143 genes were downregulated. Furthermore, the number of T regulatory cell was higher in lung adenocarcinoma with pelp1 high-expression and pelp1 expression was negatively correlated with CD274 (PDL-1) and CTLA4. Therefore, PELP1 plays an important role in the malignant behavior of NSCLC and could be a potential therapeutic target.

Altered Expression of ESR1, ESR2, PELP1 and c-SRC Genes Is Associated with Ovarian Cancer Manifestation

Ovarian cancer remains the leading cause of death due to gynecologic malignancy. Estrogen-related pathways genes, such as estrogen receptors (ESR1 and ESR2) and their coregulators, proline-, glutamic acid-, and leucine-rich protein 1 (PELP1), and proto-oncogene tyrosine-protein kinase c-Src (SRC) are involved in ovarian cancer induction and development, still they require in-depth study. In our study, tissue samples were obtained from 52 females of Caucasian descent (control group without cancerous evidence (n = 27), including noncancerous benign changes (n = 15), and the ovarian carcinoma (n = 25)). Using quantitative analyses, we investigated ESRs, PELP1, and SRC mRNA expression association with ovarian tumorigenesis. Proteins’ presence and their location were determined by Western blot and immunohistochemistry. Results showed that PELP1 and SRC expression levels were found to differ in tissues of different sample types. The expression patterns were complex and differed in the case of ovarian cancer patients compared to controls. The most robust protein immunoreactivity was observed for PELP1 and the weakest for ESR1. The expression patterns of analyzed genes represent a potentially interesting target in ovarian cancer biology, especially PELP1. This study suggests that specific estrogen-mediated functions in the ovary and ovary-derived cancer might result from different local interactions of estrogen with their receptors and coregulators.

PELP1 promotes the expression of RUNX2 via the ERK pathway during the osteogenic differentiation of human periodontal ligament stem cells

OBJECTIVE

The aim of this study was to determine the physiological function and mechanism of proline-, glutamic acid-, and leucine-rich protein 1 (PELP1) in the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) at the molecular level in vitro.

DESIGN

During the osteogenic differentiation of hPDLSCs, the change of PELP1 and the osteogenic commitment markers runt-related transcription factor 2(RUNX2), alkaline phosphatase (ALP) and osteocalcin (OCN) were monitored by quantitative real-time PCR (qRT-PCR) and western blots. To elucidate how PELP1 regulates RUNX2, the expression of RUNX2, the phosphorylation of extracellular regulated protein kinases (ERK) and subcellular location of PELP1 were detected under conditions that PELP1 was either knockdown by specific siRNA or overexpressed. A pharmacological inhibitor of ERK, U0126 was used while PELP1 was overexpressed, and the expression of RUNX2 was monitored by qRT-PCR.

RESULTS

PELP1 was upregulated during the osteogenic differentiation of hPDLSCs. Knockdown of PELP1 suppressed the expression of RUNX2, whereas overexpression of PELP1 increased RUNX2 expression. Moreover, PELP1 knockdown resulted in reduced ERK phosphorylation and RUNX2 expression, and PELP1 overexpression induced RUNX2 expression was inhibited by U0126 in the hPDLSCs.

CONCLUSIONS

PELP1 regulates the expression of RUNX2 during the osteogenic differentiation of hPDLSCs and that the ERK pathway is involved in this process.

Extracellular vesicles and post-translational protein deimination signatures in haemolymph of the American lobster (Homarus americanus)

The American lobster (Homarus americanus) is a commercially important crustacean with an unusual long life span up to 100 years and a comparative animal model of longevity. Therefore, research into its immune system and physiology is of considerable importance both for industry and comparative immunology studies. Peptidylarginine deiminases (PADs) are a phylogenetically conserved enzyme family that catalyses post-translational protein deimination via the conversion of arginine to citrulline. This can lead to structural and functional protein changes, sometimes contributing to protein moonlighting, in health and disease. PADs also regulate the cellular release of extracellular vesicles (EVs), which is an important part of cellular communication, both in normal physiology and in immune responses. Hitherto, studies on EVs in Crustacea are limited and neither PADs nor associated protein deimination have been studied in a Crustacean species. The current study assessed EV and deimination signatures in haemolymph of the American lobster. Lobster EVs were found to be a poly-dispersed population in the 10-500 nm size range, with the majority of smaller EVs, which fell within 22-115 nm. In lobster haemolymph, 9 key immune and metabolic proteins were identified to be post-translationally deiminated, while further 41 deiminated protein hits were identified when searching against a Crustacean database. KEGG (Kyoto encyclopedia of genes and genomes) and GO (gene ontology) enrichment analysis of these deiminated proteins revealed KEGG and GO pathways relating to a number of immune, including anti-pathogenic (viral, bacterial, fungal) and host-pathogen interactions, as well as metabolic pathways, regulation of vesicle and exosome release, mitochondrial function, ATP generation, gene regulation, telomerase homeostasis and developmental processes. The characterisation of EVs, and post-translational deimination signatures, reported in lobster in the current study, and the first time in Crustacea, provides insights into protein moonlighting functions of both species-specific and phylogenetically conserved proteins and EV-mediated communication in this long-lived crustacean. The current study furthermore lays foundation for novel biomarker discovery for lobster aquaculture.

PELP1 is a novel oncogene in gastric tumorigenesis and negatively regulated by miR-15 family microRNAs

BACKGROUD

Gastric cancer (GC) is one of the leading causes of cancer-related death in East Asia and some South American countries, but its mechanism has not been clarified clearly. Proline-, glutamic acid-, and leucine-rich protein-1 (PELP1), a co-regulatory molecule of estrogen receptor α (ER α), is up-regulated in series of cancers such as endometrial carcinoma, ovarian cancer, colorectal cancer, breast cancer, and non-small cell lung cancer. However, PELP1's role in GC is still obscure, and its aberrant expression in cancers also remains to be explained.

METHODS

Immunohistochemical staining and Real-time PCR were used to compare the expression level of PELP1 in GC tissues and adjacent tissues. Western blot was used to detect the expression of PELP1 in cell lines. Kaplan-meier analysis and chi-square test were applied to evaluate the potential of PELP1 to function as a cancer biomarker. RNA interference was used to inhibit PELP1 expression in GC cells, followed by detecting cell proliferation, apoptosis, migration and invasion. Luciferase assay was conducted to validate whether miR-15 family members can directly target PELP1.

RESULTS

In this study, we validated that PELP1 was significantly up-regulated in GC samples and cell lines. It was also demonstrated that the up-regulation of PELP1 was associated with several clinicopathologic features such as tumor diameter (P< 0.001), serum CEA level (P= 0.034), and lymphatic metastasis (P= 0.0009) of GC patients, and its high expression was correlated with shorter disease-free survival and overall survival of the patients. Knockdown of PELP1 remarkably arrested the proliferationï¼ migration and invasion, while promoted apoptosis. We also confirmed that miR-15 family microRNAs, most of which were down-regulated and tumor suppressor in cancers, were posttranscriptional regulators of PELP1.

CONCLUSION

In conclusion, we demonstrated that PELP1 was an oncogene of GC associated with patients' prognosis and miR-15 family members contributed to its aberrant expression in cancers.

PELP1: a key mediator of oestrogen signalling and actions in the brain

Proline-, glutamic acid- and leucine-rich protein 1 (PELP1) is an oestrogen receptor (ER) coregulator protein identified by our collaborative group. Work from our laboratory and others has shown that PELP1 is a scaffold protein that interacts with ERs and kinase signalling factors, as well as proteins involved in chromatin remodelling and DNA repair. Its role in mediating 17β-oestradiol (E₂ ) signalling and actions has been studied in detail in cancer cells, although only recently has attention turned to its role in the brain. In this review, we discuss the tissue, cellular and subcellular localisation of PELP1 in the brain. We also discuss recent evidence from PELP1 forebrain-specific knockout mice demonstrating a critical role of PELP1 in mediating both extranuclear and nuclear ER signalling in the brain, as well as E₂ -induced neuroprotection, anti-inflammatory effects and regulation of cognitive function. Finally, the PELP1 interactome and unique gene network regulated by PELP1 in the brain is discussed, especially because it provides new insights into PELP1 biology, protein interactions and mechanisms of action in the brain. As a whole, the findings discussed in the present review indicate that PELP1 functions as a critical ER coregulator in the brain to mediate E₂ signalling and actions.

PELP1: Structure, biological function and clinical significance

Proline-, glutamic acid-, and leucine-rich protein 1 (PELP1) is a scaffolding protein that functions as a coregulator of several transcription factors and nuclear receptors. Notably, the PELP1 protein has a histone-binding domain, recognizes histone modifications and interacts with several chromatin-modifying complexes. PELP1 serves as a substrate of multitude of kinases, and phosphorylation regulates its functions in various complexes. Further, PELP1 plays essential roles in several pathways including hormonal signaling, cell cycle progression, ribosomal biogenesis, and the DNA damage response. PELP1 expression is upregulated in several cancers, its deregulation contributes to therapy resistance, and it is a prognostic biomarker for breast cancer survival. Recent evidence suggests that PELP1 represents a novel therapeutic target for many hormonal cancers. In this review, we summarized the emerging biological properties and functions of PELP1.

Identification of STAM1 as a novel effector of ventral projection of spinal motor neurons

During spinal cord development, motor neuron (MN) axons exit the spinal cord ventrally, although the molecular basis for this process remains poorly understood. STAM1 and Hrs form a complex involved with endosomal targeting of cargo proteins, including the chemokine receptor CXCR4. Interestingly, the absence of CXCR4 signaling in spinal MNs is known to enforce improper extension of the axons into the dorsal side of the spinal cord. Here we report that the MN-specific Isl1-Lhx3 complex directly transactivates the Stam1 gene and STAM1 functions in determining the ventral spinal MN axonal projections. STAM1 is co-expressed with Hrs in embryonic spinal MNs, and knock-down of STAM1 in the developing chick spinal cord results in down-regulation of the expression of CXCR4, accompanied by dorsally projecting motor axons. Interestingly, overexpression of STAM1 or CXCR4 also results in dorsal projection of motor axons, suggesting that proper CXCR4 protein level is critical for the ventral motor axon trajectory. Our results reveal a critical regulatory axis for the ventral axonal trajectory of developing spinal MNs, consisting of the Isl1-Lhx3 complex, STAM1 and CXCR4.

The pattern of proline, glutamic acid, and leucine-rich protein 1 expression in Chinese women with primary breast cancer

BACKGROUND

Disparities of biomarkers' expression in breast cancer across different races and ethnicities have been well documented. Proline, glutamic acid, and leucine-rich protein 1 (PELP1), a novel ER coregulator, has been considered as a promising biomarker of breast cancer prognosis; however, the pattern of PELP1 expression in Chinese women with breast cancer has never been investigated. This study aims to provide useful reference on possible racial or ethnic differences of PELP1 expression in breast cancer by exploring the pattern of PELP1 expression in Chinese women with primary breast cancer.

METHODS

The expression of PELP1 in primary breast cancer samples from 130 Chinese female patients was detected by immunohistochemistry and correlated to other clinicopathological parameters; for comparison, the expression of PELP1 in 26 benign breast fibroadenomas was also examined.

RESULTS

The overall value of the PELP1 H-score in breast cancer was significantly higher than that in breast fibroadenoma (p<0.001). In our breast cancer patients, the ER/HER-2-positive group had significantly higher PELP1 H-scores than their negative counterparts (p=0.003 for ER and p=0.022 for HER-2); the Ki-67-high group also showed significantly higher PELP1 H-scores than the Ki-67-low group (p=0.008). No significant association between PELP1 H-scores and other clinicopathological parameters was found. Finally, the PELP1 H-score in breast cancers of the luminal B subtype was significantly higher than that in the triple negative subtype (p=0.002).

CONCLUSION

Overexpression of PELP1 in Chinese women with primary breast cancer appears to be associated with biomarkers of poor outcome; these results are similar to other reports based on Western populations.

PELP1: a review of PELP1 interactions, signaling, and biology

Proline, glutamic acid, and leucine rich protein 1 (PELP1) is a large multi-domain protein that has been shown to modulate an increasing number of pathways and biological processes. The first reports describing the cloning and characterization of PELP1 showed that it was an estrogen receptor coactivator. PELP1 has now been shown to be a coregulator for a growing number of transcription factors. Furthermore, recent reports have shown that PELP1 is a member of chromatin remodeling complexes. In addition to PELP1 nuclear functions, it has been shown to have cytoplasmic signaling functions as well. In the cytoplasm PELP1 acts as a scaffold molecule and mediates rapid signaling from growth factor and hormone receptors. PELP1 signaling ultimately plays a role in cancer biology by increasing proliferation and metastasis, among other cellular processes. Here we will review (1) the cloning and characterization of PELP1 expression, (2) interacting proteins, (3) PELP1 signaling, and (4) PELP1-mediated biology.

Vitamin C induces periodontal ligament progenitor cell differentiation via activation of ERK pathway mediated by PELP1

The differentiation of periodontal ligament (PDL) progenitor cells is important for maintaining the homeostasis of PDL tissue and alveolar bone. Vitamin C (VC), a water-soluble nutrient that cannot be biosynthesized by humans, is vital for mesenchymal stem cells differentiation and plays an important role in bone remodeling. Therefore, the objective of this study was to determine the function and mechanism of VC in PDL progenitor cells osteogenic differentiation at the molecular level. We demonstrated that VC could induce the osteogenic differentiation and maturation of PDL progenitor cell without other osteogenic agents. During the process, VC preferentially activated ERK1/2 but did not affect JNK or p38. Co-treatment with ERK inhibitor effectively decreased the Vitamin C-induced expression of Runx2. ERK inhibitor also abrogated Vitamin C-induced the minimized nodules formation. PELP1, a nuclear receptor co-regulator, was up-regulated under VC treatment. PELP1 knockdown inhibited ERK phosphorylation. The overexpression of PELP1 had a positive relationship with Runx2 expression. Taken together, we could make a conclude that VC induces the osteogenic differentiation of PDL progenitor cells via PELP1-ERK axis. Our finding implies that VC may have a potential in the regeneration medicine and application to periodontitis treatment.

Scaffolding proteins mediating membrane-initiated extra-nuclear actions of estrogen receptor

Estrogen mediates biological effects on cell proliferation, differentiation, and homeostasis through estrogen receptor (ER). In addition to functioning as a ligand-activated nuclear transcription factor to directly regulate gene transcription, ER also mediates rapid activation of signaling pathways independent of its transcriptional activity. A subpopulation of ER localized to the cell membrane or cytoplasm has been proposed to mediate ER activation of signaling pathways. This review focuses on recent advances in our understanding of mechanisms responsible for ER cytoplasm/membrane localization, where rapid extra-nuclear signaling is initiated. These mechanisms include lipid modification of the receptor (palmitoylation) and interactions with membrane and cytoplasmic adaptor proteins including caveolins, striatin, p130Cas, Shc, HPIP, MTA-1s, and MNAR/PELP1. While it is clear that ER mediates rapid extra-nuclear signaling resulting in activation of signaling pathways such as Src/MAPK and PI-3 kinase/Akt, how ER extra-nuclear signaling influences overall ER/estrogen physiology is still not well understood. Future studies defining physiological roles of ER extra-nuclear actions and crosstalk with its nuclear counterparts will be important to our overall understanding of estrogen and ER biological functions.

PELP1: A novel therapeutic target for hormonal cancers

Recent studies implicate that the estrogen receptor (ER) coregulator proline-, glutamic acid-, and leucine-rich protein (PELP) 1 as playing critical roles in ER-genomic, ER-nongenomic, and ER-signaling cross talk with growth factor signaling pathways. PELP1 expression is deregulated in hormonal cancers and recent studies further elucidated the molecular mechanisms by which PELP1 regulates hormone therapy response. Although PELP1 is important for normal functions of the ER, the possibility to target ER-PELP1 axis appears to be an effective strategy for preventing hormonal carcinogenesis and therapy resistance. Thus, PELP1 may be useful as prognostic marker for hormonal cancers and PELP1 signaling may be useful to generate targeted therapeutics to overcome hormonal therapy resistance.

ESCRT & Co

Components of the ESCRT (endosomal sorting complex required for transport) machinery mediate endosomal sorting of ubiquitinated membrane proteins. They are key regulators of biological processes important for cell growth and survival, such as growth-factor-mediated signalling and cytokinesis. In addition, enveloped viruses, such as HIV-1, hijack and utilize the ESCRTs for budding during virus release and infection. Obviously, the ESCRT-facilitated pathways require tight regulation, which is partly mediated by a group of interacting proteins, for which our knowledge is growing. In this review we discuss the different ESCRT-modulating proteins and how they influence ESCRT-dependent processes, for example, by acting as positive or negative regulators or by providing temporal and spatial control. A number of the interactors influence the classical ESCRT-mediated process of endosomal cargo sorting, for example, by modulating the interaction between ubiquitinated cargo and the ESCRTs. Certain accessory proteins have been implicated in regulating the activity or steady-state expression levels of the ESCRT components, whereas other interactors control the cellular localization of the ESCRTs, for example, by inducing shuttling between cytosol and nucleus or endosomes. In conclusion, the discovery of novel interactors has and will extend our knowledge of the biological roles of ESCRTs.

Extranuclear coactivator signaling confers insensitivity to tamoxifen

PURPOSE

Tamoxifen is one of many standard therapeutic options currently available for estrogen receptor-alpha-positive breast cancer patients. Emerging data have suggested that levels of estrogen receptor coregulatory proteins play a significant role in acquiring resistance to antiestrogen action. It has been suggested that high levels of estrogen receptor coactivators and its mislocalization may enhance the estrogen agonist activity of tamoxifen and contribute to tamoxifen resistance.

EXPERIMENTAL DESIGN

In an effort to understand the impact of nongenomic signaling and its contribution to hormone resistance in a whole-animal setting, we generated a transgenic mouse expressing a cytoplasmic version of proline-, glutamic acid-, and leucine-rich protein-1 (PELP1) mutant defective in its nuclear translocation (PELP1-cyto) and implanted these mice with tamoxifen pellets to assess its responsiveness.

RESULTS

We show that mammary glands from these mice developed widespread hyperplasia with increased cell proliferation and enhanced activation of mitogen-activated protein kinase and AKT as early as 12 weeks of age. Treatment with tamoxifen did not inhibit this hyperplasia; instead, such treatment exaggerated hyperplasia with an enhanced degree of alteration, indicative of hypersensitivity to tamoxifen. Analysis of molecular markers in the transgenic mammary glands from the tamoxifen-treated transgenic mice showed higher levels of proliferation markers proliferating cell nuclear antigen and activated mitogen-activated protein kinase than in untreated PELP1-cyto cell-derived mice. We also found that nude mice with MCF-7/PELP1-cyto cell-derived tumor xenografts did not respond to tamoxifen. Using immunohistochemical analysis, we found that 43% of human breast tumor samples had high levels of cytoplasmic PELP1, which shows a positive correlation between tumor grade and proliferation. Patients whose tumors had high levels of cytoplasmic PELP1 exhibited a tendency to respond poorly to tamoxifen compared with patients whose tumors had low levels of cytoplasmic PELP1.

CONCLUSIONS

These findings suggest that PELP1 localization could be used as a determinant of hormone sensitivity or vulnerability. The establishment of the PELP1-cyto transgenic mouse model is expected to facilitate the development of preclinical approaches for effective intervention of breast tumors using cytoplasmic coregulators and active nongenomic signaling.

PELP1--a novel estrogen receptor-interacting protein

PELP1 (proline-, glutamic acid-, and leucine-rich protein-1) is a novel estrogen receptor (ER)-interacting protein that has been implicated to be important for mediation of both the genomic and nongenomic signaling of 17beta-estradiol (E2). PELP1 contains ten nuclear receptor-interacting boxes (LXXLL motifs), which allow it to interact with ER and other nuclear hormone receptors, a zinc finger, a glutamic acid-rich domain, and two proline-rich domains. The proline-rich regions contain several consensus PXXP motifs, which allow PELP1 to couple the ER with SH3 domain-containing kinase signaling proteins, such as Src and PI3K P85 regulatory subunit. PELP1 is expressed in many different brain regions, including the hippocampus, hypothalamus, and cerebral cortex. Further work has demonstrated that PELP1 is colocalized with ER-alpha in neurons in various brain regions. PELP1 is primarily expressed in neurons, with some expression also observed in glia. Subcellular localization studies revealed that PELP1 is highly localized in the cell nucleus of neurons, with some cytoplasm localization as well, and PELP1 is also localized at synaptic sites. Work in other tissues has demonstrated that PELP1 is critical for nongenomic and genomic signaling by E2, as PELP1 knockdown studies significantly attenuates E2-induced activation of ERK and Akt signaling pathways, and inhibits E2 genomic transcriptional effects on gene expression in breast cancer cells. Preliminary studies in the brain, suggests that similar roles may exist for PELP1 in the brain, but this remains to be established, and further work to characterize the precise roles and functions of PELP1 in the brain are needed.

DOA1/UFD3 plays a role in sorting ubiquitinated membrane proteins into multivesicular bodies

Ubiquitin (Ub) is a sorting signal that targets integral membrane proteins to the interior of the vacuole/lysosome by directing them into lumenal vesicles of multivesicular bodies (MVBs). The Vps27-Hse1 complex, which is homologous to the Hrs-STAM complex in mammalian cells, serves as a Ub-sorting receptor at the surface of early endosomes. We have found that Hse1 interacts with Doa1/Ufd3. Doa1 is known to interact with Cdc48/p97 and Ub and is required for maintaining Ub levels. We find that the Hse1 Src homology 3 domain binds directly to the central PFU domain of Doa1. Mutations in Doa1 that block Hse1 binding but not Ub binding do not alter Ub levels but do result in the missorting of the MVB cargo GFP-Cps1. Loss of Doa1 also causes a synthetic growth defect when combined with loss of Vps27. Unlike the loss of Doa1 alone, the doa1Delta vps27Delta double mutant phenotype is not suppressed by Ub overexpression, demonstrating that the effect is not due to indirect consequence of lowered Ub levels. Loss of Doa1 results in a defect in the accumulation of GFP-Ub within yeast vacuoles, implying that there is a reduction in the flux of ubiquitinated membrane proteins through the MVB pathway. This defect was also reflected by an inability to properly sort Vph1-GFP-Ub, a modified subunit of the multiprotein vacuolar ATPase complex, which carries an in-frame fusion of Ub as an MVB sorting signal. These results reveal novel roles for Doa1 in helping to process ubiquitinated membrane proteins for sorting into MVBs.

Differential expression of hormonal and growth factor receptors in salivary duct carcinomas: biologic significance and potential role in therapeutic stratification of patients

Salivary duct carcinoma (SDC), a rare malignancy, manifests remarkable morphologic and biologic resemblance to high-grade mammary ductal carcinoma. We contend that, similar to mammary ductal carcinoma, hormones and growth factors may play a role in SDCs. Our aim was to determine the incidence and clinical significance of the expression of several hormone and growth factor receptors and evaluate their potential in therapeutic stratification of SDC patients in the largest cohort studied to date. Eighty-four archived tumor tissue blocks were analyzed immunohistochemically for expression of estrogen receptor-beta (ERbeta), androgen receptor (AR), and proline, glutamic acid, and leucine-rich protein-1 and growth factor receptors HER-2 and epidermal growth factor receptor. The results were correlated with available pathologic, demographic, and clinical data from 59 of 84 cases. Proline, glutamic acid, and leucine-rich protein-1, ERbeta, and AR were expressed individually in 94% (71/76), 73% (57/80), and 67% (56/84) of SDCs, respectively, and coexpressed in 45% (34/75). AR was expressed significantly more often in SDCs of men than in SDCs of women [79% (35/57) vs. 33% (9/27), P<0.001]. Epidermal growth factor receptor and HER-2 were overexpressed individually in 48% (40/83) and 25% (21/84), respectively, and co-overexpressed in 12% (10/83). Survival decreased significantly in patients with lymph node metastasis (P=0.002) and positive surgical margins (P=0.006). Lack of ERbeta expression correlated with increased local and regional recurrence (P=0.05 and P=0.002, respectively). Together, these results indicate that (a) ERbeta down-regulation is associated with adverse clinical features, (b) lymph node and surgical margin status are significant survival factors, and (c) the differential expression of these hormones and growth factor receptors may assist in triaging patients with SDC for novel therapies.

Biogenesis and function of multivesicular bodies

The two major cellular sites for membrane protein degradation are the proteasome and the lysosome. Ubiquitin attachment is a sorting signal for both degradation routes. For lysosomal degradation, ubiquitination triggers the sorting of cargo proteins into the lumen of late endosomal multivesicular bodies (MVBs)/endosomes. MVB formation occurs when a portion of the limiting membrane of an endosome invaginates and buds into its own lumen. Intralumenal vesicles are degraded when MVBs fuse to lysosomes. The proper delivery of proteins to the MVB interior relies on specific ubiquitination of cargo, recognition and sorting of ubiquitinated cargo to endosomal subdomains, and the formation and scission of cargo-filled intralumenal vesicles. Over the past five years, a number of proteins that may directly participate in these aspects of MVB function and biogenesis have been identified. However, major questions remain as to exactly what these proteins do at the molecular level and how they may accomplish these tasks.

Identifying the estrogen receptor coactivator PELP1 in autophagosomes

Resveratrol, a well-established phytoestrogen and chemopreventive agent, has gained much attention among oncologists because it can act as both estrogen receptor agonist and antagonist, depending on dosage and cell context. It is increasingly accepted that steroidal receptor coregulators may also function in the cytoplasmic compartment. Deregulation and altered localization of these coregulators could influence target gene expression and participate in the development of hormone-responsive cancers. Proline-, glutamic acid-, and leucine-rich protein-1 (PELP1), a novel estrogen receptor (ER) coactivator, plays an important role in the genomic and nongenomic actions of ER. Furthermore, recent studies have shown that differential compartmentalization of PELP1 could be crucial in modulating sensitivity to tamoxifen. In this study, we investigated the role of PELP1 in resveratrol-induced autophagy in lung cancer and salivary gland adenocarcinoma cell lines. Resveratrol reversibly inhibited the growth of these cancer cell lines and induced autophagy, as evidenced by microtubule-associated protein 1 light chain 3 (LC3) up-regulation in a time-dependent and 3-methyladenine-sensitive manner. Confocal microscopic analysis showed that resveratrol induced PELP1 accumulation in autophagosomes with green fluorescent protein-LC3. The intermediary molecule involved in PELP1 accumulation in resveratrol-induced autophagosomes is hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), a trafficking molecule that binds to PELP1. These results identify PELP1 for the first time in autophagosomes, implying that both PELP1 and HRS reallocate to autophagosomes in response to resveratrol treatment, which might be important in the process of autophagy in the cancer cells.

c-Src/Histone Deacetylase 3 Interaction Is Crucial for Hepatocyte Growth Factor–Dependent Decrease of CXCR4 Expression in Highly Invasive Breast Tumor Cells

Hepatocyte growth factor (HGF), a cytokine of tumor microenvironment, exerts opposite effects on CXCR4 expression in MCF-7 (low invasive) and MDA-MB231 (highly invasive) breast carcinoma cells, and here, we show that completely different molecular mechanisms downstream of c-Src activation were involved. As experimental models, we used cells transfected with two CXCR4 promoter constructs and treated with HGF or cotransfected with c-Src wild-type (Srcwt) expression vector; phospho-c-Src formation was enhanced in both cell lines. In MCF-7 cells, consistent with activations of CXCR4Luc constructs after HGF treatment and Srcwt expression, Ets1 and nuclear factor-kappaB (NF-kappaB) transcription factors were activated. In contrast, in MDA-MB231 cells, CXCR4Luc construct, Ets1 and NF-kappaB activities decreased. The divergence point seemed to be downstream of HGF/c-Src and consisted in the interaction between c-Src and the substrate histone deacetylase 3 (HDAC3). Only in MDA-MB231 cells, HDAC3 level was enhanced in membranes and nuclei 30 min after HGF and colocalized/coimmunoprecipitated with phospho-c-Src and phosphotyrosine. Thus, the CXCR4 induction by HGF in MCF-7 cells required NF-kappaB and Ets1 activations, downstream of phosphoinositide-3-kinase/Akt, whereas in HGF-treated MDA-MB231 cells, HDAC3 activation via c-Src probably caused a reduction of transcription factor activities, such as that of NF-kappaB. These results indicate possible roles of HGF in invasive growth of breast carcinomas. By enhancing CXCR4 in low invasive tumor cells, HGF probably favors their homing to secondary sites, whereas by suppressing CXCR4 in highly invasive cells, HGF might participate to retain them in the metastatic sites.

Functional and biological properties of the nuclear receptor coregulator PELP1/MNAR

Proline-, glutamic acid-, and leucine-rich protein (PELP)1, also known as modulator of nongenomic actions of the estrogen receptor (MNAR), is a novel nuclear receptor coregulator with a multitude of functions. PELP1/MNAR serves as a scaffolding protein that couples various signaling complexes with nuclear receptors and participates in genomic and nongenomic functions. Recent data suggest that PELP1/MNAR expression is deregulated in several cancers, including breast, endometrial, prostate, and ovarian cancer, and that PELP1/MNAR interacts with several oncogenes. In this review, we summarize the emerging biological properties and functions of PELP1/MNAR.

Emerging significance of ER-coregulator PELP1/MNAR in cancer

The estrogen receptors ERalpha and ERbeta have been implicated in the progression of a wide variety of cancers. The actions of ER are regulated by ER coregulator proteins, including proline-, glutamic acid- and leucine-rich-protein-1 (PELP1/MNAR). PELP1 has been shown to participate in both genomic and nongenomic functions of ER. The expression and localization of PELP1/MNAR are deregulated in a wide variety of tumors and have been implicated in the development of hormonal resistance in cancer cell lines. Emerging data suggest that PELP1/MNAR interacts with many proteins and activates several oncogenes, including Src kinase, phosphotidyl inositol 3 kinase (PI3K), and signal transducers and activators of transcription 3 (STAT3). These new results suggest that PELP1/MNAR may act as an oncogene as well as cooperating with other oncogenes. Thus, PELP1/MNAR may contribute to the tumorigenic potential of cancer cells by serving as a scaffolding protein that couples various signaling complexes with ER.

Estrogen deprivation for breast cancer prevention

Estrogen deprivation (ED) either as a result of a natural or artificial menopause or the use of aromatase inhibitors in postmenopausal women results in a reduction of the incidence of breast cancer. Two major clinical trials of this approach comparing anastrozole or exemestane with placebo are currently in progress to test their efficacy for prevention. Reduction of contralateral breast lesions by at least 50% compared with tamoxifen indicate this approach has promise. The target lesion within the breast for ED is not known but we argue that hyperplastic enlarged lobular units (HELUs) as well as more advanced lesions are good candidates. A major problem for ED is de novo or acquired resistance to its effectiveness. We discuss potential mechanisms of resistance including high concentrations of tissue estrogens, increase in growth factor, and signal transduction pathways within the epithelial cell and activation of paracrine pathways from breast adipocytes, macrophages and fibroblasts. It may be possible to increase effectiveness of ED by additional preventive agents or by lifestyle alterations.

Structure-function relationship of estrogen receptor alpha and beta: impact on human health

17Beta-estradiol (E2) controls many aspects of human physiology, including development, reproduction and homeostasis, through regulation of the transcriptional activity of its cognate receptors (ERs). The crystal structures of ERs with agonists and antagonists and the use of transgenic animals have revealed much about how hormone binding influences ER conformation(s) and how this conformation(s), in turn, influences the interaction of ERs with co-activators or co-repressors and hence determines ER binding to DNA and cellular outcomes. This information has helped to shed light on the connection between E2 and the development or progression of numerous diseases. Current therapeutic strategy in the treatment of E2-related pathologies relies on the modulation of ER trancriptional activity by anti-estrogens; however, data accumulated during the last five years reveal that ER activities are not only restricted to the nucleus. ERs are very mobile proteins continuously shuttling between protein targets located within various cellular compartments (e.g., membrane, nucleus). This allows E2 to generate different and synergic signal transduction pathways (i.e., non-genomic and genomic) which provide plasticity for cell response to E2. Understanding the structural basis and the molecular mechanisms by which ER transduce E2 signals in target cells will allow to create new pharmacologic therapies aimed at the treatment of a variety of human diseases affecting the cardiovascular system, the reproductive system, the skeletal system, the nervous system, the mammary gland, and many others.

Comprehensive analysis of recent biochemical and biologic findings regarding a newly discovered protein-PELP1/MNAR

Estradiol (E2) and estrogen receptor (ER) signaling have been implicated in the development and progression of several cancers. Emerging evidence suggests that the status of ER coregulators in tumor cells plays an important role in hormonal responsiveness and tumor progression. Proline, glutamic acid, and leucine-rich protein-1 (PELP1/MNAR)-a novel ER coactivator that plays an essential role in the ER's actions and its expression-is deregulated in several hormonal responsive cancers. The precise function of PELP1/MNAR in cancer progression remains unclear, but PELP1 appears to function as a scaffolding protein, coupling ER with several proteins that are implicated in oncogenesis. Emerging evidence suggests that PELP1/MNAR increases E2-mediated cell proliferation and participates in E2-mediated tumorigenesis and metastasis.

Essential role of KIBRA in co-activator function of dynein light chain 1 in mammalian cells

Recently dynein light chain 1 (DLC1), a cytoskeleton signaling component, has been shown to interact with and transactivate estrogen receptor-alpha (ER), leading to increased expression of ER target genes and growth stimulation of breast cancer cells. However, the molecular mechanism by which DLC1 regulates the ER pathway remains poorly understood. To gain insights into the putative mechanism, here we set out to identify novel DLC1-interacting proteins. We identified KIBRA, a WW domain- and a glutamic acid stretch-containing protein, as a DLC1-binding protein and showed that it interacts with DLC1 both in vitro and in vivo. We found that KIBRA-DLC1 complex is recruited to ER-responsive promoters. We also found that KIBRA-DLC1 interaction is mandatory for the recruitment and transactivation functions of ER or DLC1 to the target chromatin. Finally we found that KIBRA interacts with histone H3 via its glutamic acid-rich region and that such interaction might play a mechanistic role in conferring an optimal ER transactivation function as well as the proliferation of ligand-stimulated breast cancer cells. Together these findings indicate that DLC1-KIBRA interaction is essential for ER transactivation in breast cancer cells.

Membrane-associated STAT3 and PY-STAT3 in the Cytoplasm

Signal transduction from the plasma membrane to the nucleus by STAT proteins is widely represented as exclusively a soluble cytosolic process. Using cell-fractionation methods, we observed that approximately 5% of cytoplasmic STAT3 was constitutively associated with the purified early endosome (EE) fraction in human Hep3B liver cells. By 15-30 min after interleukin-6 (IL-6) treatment, up to two-thirds of cytoplasmic Tyr-phosphorylated STAT3 can be associated with the purified early endosome fraction (Rab-5-, EEA1-, transferrin receptor-, and clathrin-positive fraction). Electron microscopy, immunofluorescence, and detergent dissection approaches confirmed the association of STAT3 and PY-STAT3 with early endosomes. STAT3 was constitutively associated with clathrin heavy chain in membrane and in the 1- to 2-MDa cytosolic complexes. The membrane association was dynamic in that, within 15 min of treatment with the vicinal-thiol cross-linker phenylarsine oxide, there was a dramatic increase in bulk STAT3 association with sedimentable membranes. The functional contribution of PY-STAT3 association with the endocytic pathway was evaluated in transient transfection assays using IL-6-inducible STAT3-reporter-luciferase constructs and selective regulators of this pathway. STAT3-transcriptional activation was inhibited by expression constructs for dominant negative dynamin K44A, epsin 2a, amphiphysin A1, and clathrin light chain but enhanced by that for the active dynamin species MxA. Taken together, these studies emphasize the contribution of the endocytic pathway to productive IL-6/STAT3 signaling.

Cloning, distribution, and colocalization of MNAR/PELP1 with glucocorticoid receptors in primate and nonprimate brain

MNAR/PELP1 (see text) is a newly identified scaffold protein/coactivator initially thought to modulate nongenomic and genomic actions of the estrogen receptor; however, it has been recently shown to interact with multiple steroid receptors, including androgen and glucocorticoid receptors. In the present study, we cloned the monkey MNAR/PELP1 gene, deduced its domain structure, examined its localization pattern and colocalization with glucocorticoid receptor in monkey brain, and determined its subcellular localization. PCR-based cloning of MNAR/PELP1 from monkey brain produced a transcript of approximately 3.4 kb which showed high homology to the human and rat MNAR/PELP1 gene. Domain analysis showed that all the key steroid-receptor-interacting (LXXLL) domains, SH3-interacting (PXXP) domains and several C-terminal glutamic-acid-rich clusters, as well as various kinase domains are conserved in the monkey MNAR/PELP1 gene. Anatomical mapping of MNAR/PELP1 immunoreactivity in several regions of the monkey brain showed a similar pattern of MNAR/PELP1 distribution as previously observed in rat and mouse brains. MNAR/PELP1 also showed an absolute colocalization with glucocorticoid receptors in both primate and nonprimate brain, including those regions of the brain, where other steroid receptors are not significantly expressed, such as hippocampus, striatum, and thalamus - suggesting that MNAR/PELP1 may modulate glucocorticoid actions in the brain. Finally, ultrastructural electron microscopic studies showed that MNAR/PELP1-reactive gold particles are located within nucleus, cytoplasm, dendritic/synaptic terminals, and astrocytic processes. As a whole, the studies demonstrate that MNAR/PELP1 is expressed and colocalizes with glucocorticoid receptors in monkey and rat brains and may have multiple cellular functions based on its subcellular localizations.