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Menaquinones are lipoquinones that consist of a headgroup (naphthoquinone, menadione) and an isoprenyl sidechain. They function as electron transporters in prokaryotes such as Mycobacterium tuberculosis. For these studies, we used Langmuir monolayers and microemulsions to investigate how the menaquinone headgroup (menadione) and the menahydroquinone headgroup (menadiol) interact with model membrane interfaces to determine if differences are observed in the location of these headgroups in a membrane. It has been suggested that the differences in the locations are mainly caused by the isoprenyl sidechain rather than the headgroup quinone-to-quinol reduction during electron transport. This study presents evidence that suggests the influence of the headgroup drives the movement of the oxidized quinone and the reduced hydroquinone to different locations within the interface. Utilizing the model membranes of microemulsions and Langmuir monolayers, it is determined whether or not there is a difference in the location of menadione and menadiol within the interface. Based on our findings, we conclude that the menadione and menadiol may reside in different locations within model membranes. It follows that if menaquinone moves within the cell membrane upon menaquinol formation, it is due at least in part, to the differences in the properties of headgroup interactions with the membrane in addition to the isoprenyl sidechain. Key words: menaquinone, menadione, menadiol, Langmuir monolayer, reverse micelle. Les menaquinones sont des lipoquinones formees d'un groupement de tete (naphtoquinone, menadione) et d'une chaine laterale isoprenyle. Elles servent de transporteurs d'electrons dans les procaryotes tels que Mycobacterium tuberculosis. Dans le cadre des presents travaux, nous avons employe des monocouches de Langmuir et des microemulsions pour etudier la maniere dont le groupement de tete de la menaquinone (la menadione) et le groupement de tete de la menahydroquinone (le menadiol) interagissent avec les interfaces du modele membranaire. Cette etude avait pour but de determiner si des differences peuvent etre decelees quant aux endroitsou ces groupementsde tete se situent a l'interieur d'une membrane. L'hypothese selon laquelle ces differences de position seraient essentiellement attribuables a la chaine laterale plutot qu'a la reduction de la quinone en quinol durant le transport d'electrons a ete posee. Cette etude presente des elements qui tendent a demontrer que la quinone oxydee et l'hydroquinone reduite se deplacent a des endroits differents dans la membrane cellulaire, et ce, sans influence de la chaine laterale. A l'aide de membranes modeles de microemulsions et de monocouches de Langmuir, nous avons pu determiner s'il y avait ou non une difference de position entre la menadione et le menadiol dans la membrane. Nos resultats ont permisdeconclure quela menadioneet lemenadiol peuvent se situerades endroits differents dans les membranes modeles. Par consequent, si la menaquinone sedeplace dans la membrane cellulaire lorsqu'elle se transforme en menaquinol, ce deplacement est attribuable non seulement a la chaine isoprenyle, mais aussi, du moins en partie, a la difference des proprietes des interactions entre le groupement de tete et la membrane. [Traduit par la Redaction] Mots-cles : menaquinone, menadione, menadiol, monocouche de Langmuir, micelle inversee., 1. Introduction Lipoquinones are an essential group of lipids that act as electron transfer donors and acceptors within the electron transfer complex (.1,2) One type of lipoquinone typically associated with [...]

Numb functions as an oncosuppressor by inhibiting Notch signaling and stabilizing p53. This latter effect depends on the interaction of Numb with Mdm2, the E3 ligase that ubiquitinates p53 and commits it to degradation. In breast cancer (BC), loss of Numb results in a reduction of p53-mediated responses including sensitivity to genotoxic drugs and maintenance of homeostasis in the stem cell compartment. In this study, we show that the Numb-Mdm2 interaction represents a fuzzy complex mediated by a short Numb sequence encompassing its alternatively spliced exon 3 (Ex3), which is necessary and sufficient to inhibit Mdm2 and prevent p53 degradation. Alterations in the Numb splicing pattern are critical in BC as shown by increased chemoresistance of tumors displaying reduced levels of Ex3-containing isoforms, an effect that could be mechanistically linked to diminished p53 levels. A reduced level of Ex3-less Numb isoforms independently predicts poor outcome in BCs harboring wild-type p53. Thus, we have uncovered an important mechanism of chemoresistance and progression in p53-competent BCs. [ABSTRACT FROM AUTHOR]

The vertebrate telencephalon is composed of many architectonically and functionally distinct areas and structures, with billions of neurons that are precisely connected. This complexity is fine-tuned during development by numerous genes. To identify genes involved in the regulation of telencephalic development, a specific subset of differentially expressed genes was characterized. Here, we describe a set of cDNAs encoded by genes preferentially expressed during development of the mouse telencephalon that was identified through a functional genomics approach. Of 832 distinct transcripts found, 223 (27%) are known genes. Of the remaining, 228 (27%) correspond to expressed sequence tags of unknown function, 58 (7%) are homologs or orthologs of known genes, and 323 (39%) correspond to novel rare transcripts, including 48 (14%) new putative noncoding RNAs. As an example of this latter group of novel precursor transcripts of micro-RNAs, telencephalic embryonic subtractive sequence (TESS) 24.E3 was functionally characterized, and one of its targets was identified: the zinc finger transcription factor ZFP9. The TESS transcriptome has been annotated, mapped for chromosome loci, and arrayed for its gene expression profiles during neural development and differentiation (in Neuro2a and neural stem cells). Within this collection, 188 genes were also characterized on embryonic and postnatal tissue by in situ hybridization, demonstrating that most are specifically expressed in the embryonic CNS. The full information has been organized into a searchable database linked to other genomic resources, allowing easy access to those who are interested in the dissection of the molecular basis of telencephalic development. [ABSTRACT FROM AUTHOR]

MDM2 regulates a variety of cellular processes through its dual protein:protein interaction and ubiquitin ligase activities. One major function of MDM2 is to bind and ubiquitinate P53, thereby regulating its proteasomal degradation. This function is in turn controlled by the cell fate determinant NUMB, which binds to and inhibits MDM2 via a short stretch of 11 amino acids, contained in its phosphotyrosine-binding (PTB) domain, encoded by exon 3 of the NUMB gene. The NUMB-MDM2-P53 circuitry is relevant to the specification of the stem cell fate and its subversion has been shown to be causal in breast cancer leading to the emergence of cancer stem cells. While extensive work on the evolutionary aspects of the MDM2/P53 circuitry has provided hints as to how these two proteins have evolved together to maintain conserved and linked functions, little is known about the evolution of the NUMB gene and, in particular, how it developed the ability to regulate MDM2 function. Here, we show that NUMB is a metazoan gene, which acquired exon 3 in the common ancestor of the Chordate lineage, first being present in the Cephalochordate and Tunicate subphyla, but absent in invertebrates. We provide experimental evidence showing that since its emergence, exon 3 conferred to the PTB domain of NUMB the ability to bind and to regulate MDM2 functions. [ABSTRACT FROM AUTHOR]

Multiple myeloma is still incurable due to an intrinsic aggressiveness or, more frequently, to the interactions of malignant plasma cells with the bone marrow (BM) microenvironment. Myeloma cells educate BM cells to support neoplastic cell growth, survival, acquisition of drug resistance resulting in disease relapse. Myeloma microenvironment is characterized by Notch signaling hyperactivation due to the increased expression of Notch1 and 2 and the ligands Jagged1 and 2 in tumor cells. Notch activation influences myeloma cell biology and promotes the reprogramming of BM stromal cells. In this work we demonstrate, in vitro, ex vivo and by using a zebrafish multiple myeloma model, that Jagged inhibition causes a decrease in both myeloma-intrinsic and stromal cell-induced resistance to currently used drugs, i.e. bortezomib, lenalidomide and melphalan. The molecular mechanism of drug resistance involves the chemokine system CXCR4/SDF1α. Myeloma cell-derived Jagged ligands trigger Notch activity in BM stromal cells. These, in turn, secrete higher levels of SDF1α in the BM microenvironment increasing CXCR4 activation in myeloma cells, which is further potentiated by the concomitant increased expression of this receptor induced by Notch activation. Consistently with the augmented pharmacological resistance, SDF1α boosts the expression of BCL2, Survivin and ABCC1. These results indicate that a Jagged-tailored approach may contribute to disrupting the pharmacological resistance due to intrinsic myeloma cell features or to the pathological interplay with BM stromal cells and, conceivably, improve patients' response to standard-of-care therapies., (Copyright© 2020 Ferrata Storti Foundation.)

The transduction of Notch signal plays an intricate role in cell differentiation and pathogenesis of haematological malignancies as well as in certain congenital conditions. The functionality of Notch signalling was tested using HES1 gene activation. SEL1 gene product has been postulated to be a negative regulator of Notch signalling. We investigated the relationship between Notch signalling and the expression of SEL1L gene in a number of leukaemia and lymphoma cells in culture. The cell lines could be separated into two groups. Group 1 contained lymphoma cell lines in which Notch signalling was intact; of these 4 cell lines were SEL1L+/HES1- and 3 SEL1L-/HES1-. Notch signalling was not subverted by EBNA2 expression in these lymphoma cells. In Group 2 cell lines Notch signalling was constitutively active but 6 out of 7 cell lines expressed SEL1L at high levels. In summary, a majority of cell lines of both groups express SEL1L and no inverse relationship is evident between SEL1L expression and the status of Notch signalling. The present investigation therefore suggests that SEL1L may not exert a negative regulatory influence on Notch signalling. No genomic alterations affecting SEL1L were detected either in the lymphoma or T-ALL cell lines tested. Taken together the present findings do not support the postulated negative regulatory role for SEL1L in Notch signalling.