1,720,962 research outputs found
Clathrin Heavy Chain Interacts With Estrogen Receptor α and Modulates 17β-Estradiol Signaling
No full text17β-estradiol (E2)-induced signaling and control of estrogen receptor (ER)α degradation both play a major role in breast cancer cell proliferation. We recently reported the involvement of lysosomal function in both E2-dependent ERα breakdown and E2-induced cell proliferation and thus hypothesized a role for endocytic proteins in ERα signaling. An small interfering RNA screen identified proteins that regulate intracellular endocytic traffic and whose silencing alters E2-induced ERα degradation. One such protein was the clathrin heavy chain (CHC), whose role in E2:ERα signaling to cell proliferation is unknown. Here, we show that CHC physically interacts with ERα in the cytoplasm of breast cancer cells and regulates E2-induced cell proliferation. Surprisingly, the CHC:ERα interaction is required to sustain E2 signaling but is dispensable for ERα degradation. Our data also demonstrate that many membrane trafficking proteins contribute to the regulation of ERα degradation, thus unraveling the contribution of endocytic proteins in E2:ERα signaling
Estrogen receptor α L429 and A430 regulate 17β-estradiol-induced cell proliferation via CREB1
No full text17β-Estradiol (E2)-dependent cell proliferation requires both estrogen receptor α (ERα)-based integrated control of gene transcription and kinase pathways activation. Such coordination of intracellular E2:ERα-dependent signaling mechanisms is finely tuned by receptor association with specific partner proteins. Recently, we identified the leucine (L) 429 and alanine (A) 430 within the ERα ligand binding domain as important residues for receptor non-covalent interaction to ubiquitinated species [i.e., ERα ubiquitin-binding surface (ERα UBS)] and for E2-induced ERα activation. To date, if these two ERα amino acids are involved in the control of E2-dependent pathways required for cell proliferation is unknown. Here, by using stably expressing ERα mutated in L429 and A430 (i.e., L429A,A430G-LAAG) cell lines, we show that L429 and A430 are critical for E2-induced cell proliferation, PI3K/AKT pathway activation, and ERα-mediated transcriptional changes. Moreover, we demonstrate that these two receptor structural determinants direct the E2-induced PI3K/AKT/CREB1 pathway activation and CREB1-mediated transcriptional activity that in turn control the hormone-induced cell proliferation. As a whole, our data demonstrate for the first time that the ERα UBS contributes to the modulation of E2-induced ERα-mediated cell proliferation and provide a novel connection between the receptor structure and the functional molecular mechanisms by which E2:ERα complex can regulate cell processes
Selective binding of estrogen receptor α to ubiquitin chains.
No full textUbiquitin (Ub)-binding domains (UBDs) noncovalently contact the Ub modification on binding partners. Ub possesses seven lysine (K) residues (i.e., K6, K11, K27, K29, K33, K48, and K63) that can be used to form different chains based on different Ub linkage types (e.g., monoubiquitination/polyubiquitination). Thus, different Ub-based signals exist and are decoded by UBDs. Recently, we have reported the existence of two Ub binding surfaces located within the estrogen receptor α (ERα) protein. We have shown that the leucine (L) 429 and alanine (A) 430 ERα residues direct noncovalent receptor binding to K63-based Ub chains in vitro. However, mutation of L429 and A430 residues did not completely abolish the ability of ERα to associate with Ub in cell lines. Thus, we evaluated the possibility that one or both ERα Ub binding surfaces could non-covalently interact with other Ub chains. Here, we report that ERα selectively binds to specific Ub chains based on different Ub linkages and that ERα monoubiquitination requires non-covalent ERα:Ub binding. Considering the importance of the UBD:Ub interaction in the initiation and progression of many diseases (e.g., cancer), our data provide novel insights into ERα functions that could be relevant to ERα-related diseases. © 2016 IUBMB Life, 2016
Diverse post-translational modifications of estrogen receptor α cross-talk in the coordination of 17 β-estradiol-dependent cell proliferation
No full text""The sex hormone 17-estradiol (E2) exerts its pleiotropic effects through the binding to the ligand-activated transcription factor estrogen receptor alpha (ERThe E2:ER complex regulates several physiological processes including cell survival and proliferation through transcriptional [i.e., estrogen responsive element (ERE)-based gene transcription] and non-transcriptional membrane-initiated effects (i.e., activation of signalling cascades).. Many post-translational modifications occur on ER and are regulated by E2. Indeed, E2 induces ER phosphorylation that facilitates ER-dependent gene transcription while the hormone reduces ER palmitoylation, thus modulating the amount of the receptor located at the plasma membrane and the E2 signalling to cell proliferation. The ER is also an ubiquitinated protein: ER polyubiquitination (polyUbq) increases upon E2 binding and E2-dependent ER degradation occurs in parallel to the appearance of the E2-evoked physiological effects.. However, the role of ER post-translational modifications in the regulation of the E2-dependent cell proliferation is poorly appreciated. Therefore, we analyzed here how ER phosphorylation, palmitoylation and ubiquitination influence E2-induced cell proliferation in an integrated manner.. Our results demonstrate that the polyUbq-based ER degradation cross-talks with receptor phosphorylation and palmitoylation and is required for the E2-dependent control of cell proliferation. Furthermore, the lack of ER palmitoylation fastens E2-induced polyUbq-dependent ER degradation and prevents both receptor phosphorylation and E2-dependent cell proliferation. Therefore, these data demonstrate that a code of diverse post-translational modifications occurs on ER and uncover a new model of E2:ER cellular signalling in which the E2-dependent control of ER post-translational modifications finely coordinates the E2 ability to regulate cell proliferation.. "
Ubiquitin-activating enzyme is necessary for 17β-estradiol-induced breast cancer cell proliferation and migration
No full textThe sex steroid hormone 17β-estradiol (E2) regulates breast cancer (BC) cell proliferation and migration through the activation of a plethora of signal transduction cascades (e.g., PI3K/AKT activation) starting after E2 binding to the estrogen receptor alpha (ERα). The activity of the ubiquitin (Ub)-system modulates many physiological processes (e.g., cell proliferation and migration), and recently, a specific inhibitor (Pyr-41) of the Ub-activating enzyme (E1), which works as the activator of the Ub-based signaling, has been identified to prevent the functions of the Ub-system. Here, by using Pyr-41, we studied the involvement of the Ub-system in E2-induced signaling to proliferation and migration of BC cells. Our data indicate that E1 activity is involved in the E2:ERα signaling important for cell proliferation and migration through the modulation of the E2-evoked activation of the PI3K/AKT and the p38/MAPK pathways. These discoveries indicate a new molecular circuitry that can be further explored to define new opportunities for BC treatment
Interazioni tra le attività del recettore per gli estrogeni alfa e la rete di segnali basati sull'ubiquitina
No full text17β-estradiol (E2) controls a plethora of physiological processes but plays also a critical role in breast cancer progression, thus the fine comprehension of the mechanisms that control E2-induced cell proliferation would help to identify new putative druggable targets for the treatment of breast cancer. The ubiquitin (Ub)- system is gaining much attention for cancer therapies because it allows to build a complex interactions network that is critical for signal transduction to many cellular processes. The Ub-based network depends on non-covalent binding between ubiquitinated proteins and proteins that possess an ubiquitin binding domain (UBD).
Interestingly, recent papers reported that the Ub-system deeply impacts the E2 signalling by modulating the estrogen receptor (ER) α sub-type, which is the principal mediator of the E2 mitogenic effects. In particular, while ERα polyubiquitination controls the receptor turnover and transcriptional activity, ERα monoubiquitination is required for the E2-dependent activation of rapid signalling to cell proliferation. Even if it has not been clarified how the Ub modification on ERα modulates the receptor activities, one attractive possibility is that ERα could recognize and transduce the Ub modification on itself or on interacting proteins through an UBD.
Thus, the main goal of the present PhD project was to understand the noncovalent Ub-binding abilities of ERα and their regulatory role(s) in E2-dependent cellular processes.
To this purpose, initial experiments performed in vitro showed that ERα has two different Ub-binding surfaces (UBSs): in A/B and E domains. By focusing on the E domain Ub-binding ability we identified the structural determinants required for ERα to non-covalently associate to Ub (i.e., L429, A430) in vitro and in cell lines. Next, we analyzed the regulatory role of the ERα-UBS in E2-dependent cellular processes. In particular, we found that even if the L429A,A430G (LAAG) mutation did not alter ERα ability to bind E2, cells expressing the mutant ERα did not proliferate after E2 treatment. Because the E2-dependent cell proliferation depends on the activation of extra-nuclear signalling kinases, we evaluated the activating phosphorylation of some signalling pathways activated by E2. Our results indicate that the ERα-UBS mutation impairs the E2-induced activation of the PI3K/AKT as well as the E2-induced PI3K/AKT-dependent ERα Ser118 phosphorylation. The finding that this residue is not phosphorylated in LAAG ERα cells after E2 treatment further suggested an impairment of the ERα-UBS mutant ability to mediate E2 target genes expression.
DNA Micro Arrays experiments definitively demonstrated that the LAAG mutant ERα was less transcriptionally active than the wt receptor. Interestingly, the Ingenuity Pathway Analysis helped us identifying CREB1 as another transcription factor activated by E2 through wt but not throught LAAG ERα. We found that E2 triggered CREB1 transcriptional activation through the PI3K/AKT activation and the mutations of the ERα-UBS impair this pathway. Thus, it is possible that an ERα-UBSdependent membrane complex, responsible for the E2-triggered PI3K/AKT signalling activation, controls cell proliferation through the regulation of ERα and CREB1 activation required for gene transcription.
Overall, the data reported in this PhD project indicate that the ERα possesses an UBS on its E domain that plays a critical role for E2-induced nuclear and extranuclear signalling to cell proliferation. In conclusion, our findings open new avenues in the field of E2-activated molecular mechanisms to physiological effects that now have to include also the noncovalent Ub-binding abilities of ERα. Given the key role played by ERα in breast cancer progression, the comprehension of the regulatory role of the ERα-UBS on E2 mitogenic effects reveals new putative druggable target. In this respect, the interference of the UBD:Ub interaction by using specific small molecules has been already proposed as a future pharmacological target against cancer
Identification of an estrogen receptor alpha non-covalent ubiquitin binding surface: role in 17beta-estradiol-induced transcriptional activity
No full text""Ubiquitin (Ub)-binding domains (UBDs) located in Ub receptors decode the ubiquitination signal by non-covalently engaging the Ub modification on their binding partners and transduce the Ub signalling through Ub-based molecular interactions. In this way, inducible protein ubiquitination regulates diverse biological processes. The estrogen receptor alpha (ERα) is a ligand-activated transcription factor that mediates the pleiotropic effects of the sex hormone 17β-estradiol (E2). Fine regulation of E2 pleiotropic actions depends on E2-dependent ERα association with a plethora of binding partners and\\\/or on the E2 modulation of receptor ubiquitination. Indeed, E2-induced ERα polyubiquitination triggers receptor degradation and transcriptional activity, and E2-dependent reduction in ERα monoubiquitination is crucial for E2 signalling. Monoubiquitinated proteins often contain UBDs, but whether non-covalent Ub-ERα binding could occur and play a role in E2-ERα signalling is unknown. Here, we report an Ub-binding surface within the ERα ligand binding domain that directs in vitro the receptor interaction with both ubiquitinated proteins and recombinant Ub chains. Mutational analysis reveals that ERα residues leucine 429 and alanine 430 are involved in Ub binding. Moreover, impairment of ERα association to ubiquitinated species strongly affects E2-induced ERα transcriptional activity. Considering the importance of UBDs in the Ub-based signalling network and the central role of different ERα binding partners in the modulation of E2-dependent effects, our discoveries provide novel insights into ERα activity that could also be relevant for ERα-dependent diseases."
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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