Time filter

Source Type

Coyoacán, Mexico

Trujillo-Paredes N.,Institute Biotecnologia | Valencia C.,Institute Biotecnologia | Guerrero-Flores G.,Institute Biotecnologia | Arzate D.-M.,Institute Biotecnologia | And 5 more authors.
Biology Open | Year: 2016

Notch signalling is a well-established pathway that regulates neurogenesis. However, little is known about the role of Notch signalling in specific neuronal differentiation. Using Dll1 null mice, we found that Notch signalling has no function in the specification of mesencephalic dopaminergic neural precursor cells (NPCs), but plays an important role in regulating their expansion and differentiation into neurons. Premature neuronal differentiation was observed in mesencephalons of Dll1-deficient mice or after treatment with a Notch signalling inhibitor. Coupling between neurogenesis and dopaminergic differentiation was indicated from the coincident emergence of neuronal and dopaminergic markers. Early in differentiation, decreasing Notch signalling caused a reduction in NPCs and an increase in dopaminergic neurons in association with dynamic changes in the proportion of sequentially-linked dopaminergic NPCs (Msx1/2+, Ngn2+, Nurr1+). These effects in differentiation caused a significant reduction in the number of dopaminergic neurons produced. Accordingly, Dll1 haploinsufficient adult mice, in comparison with their wild-type littermates, have a consistent reduction in neuronal density that was particularly evident in the substantia nigra pars compacta. Our results are in agreement with a mathematical model based on a Dll1-mediated regulatory feedback loop between early progenitors and their dividing precursors that controls the emergence and number of dopaminergic neurons. © 2016. Published by The Company of Biologists Ltd.

Ramirez-Sanchez I.,National Polytechnic Institute of Mexico | Mendoza-Lorenzo P.,National Autonomous University of Mexico | Zentella-Dehesa A.,Institute Fisiologia Celular | Mendez-Bolaina E.,University of Veracruz | And 6 more authors.
Biochimie | Year: 2012

Several studies have shown the importance of dystrophin-associated protein complex in the development of muscular dystrophies and dilated cardiomyopathy associated to vascular dysfunction. In vascular endothelium, dystrophin is substituted for utrophin (autosomal homolog of dystrophin); however, its role in this tissue is unknown. Therefore, it is important to obtain a more extensive knowledge of utrophin and its associated proteins in endothelial cells. In a previous study, we demonstrated the presence of utrophin-associated protein complex (UAPC) in human umbilical vein endothelial cells HUVEC, which interacts with caveolin-1 (Cav-1) and endothelial nitric oxide synthase (eNOS). Also, some of our observations suggested the presence of this complex in distinct membrane domains. Therefore, the aim of this study was to analyze the presence of the UAPC in caveolae and non-caveolae lipid rafts domains of HUVEC at baseline and with a mechanical stimulus. It was demonstrated, by subcellular fractionation and co-immunoprecipitation assays, the association of UAPC with Cav-1 and eNOS in caveolae domains, as well as its interaction with eNOS in non-caveolae lipid raft domains. Additionally, it was also observed that mechanical stress on endothelial cells induced activation and release of eNOS from both caveolae and non-caveolae lipid raft associated to UAPC. Together these results suggest that UAPC located in caveolae and non-caveolae lipid raft domains of HUVECs may have a mechanosensory function that could participate in the control of eNOS activity. © 2012 Published by Elsevier Masson SAS. All rights reserved.

Frauenfeld J.,Ludwig Maximilians University of Munich | Frauenfeld J.,Munich Center for Integrated Protein Science | Gumbart J.,University of Illinois at Urbana - Champaign | Sluis E.O.V.D.,Ludwig Maximilians University of Munich | And 14 more authors.
Nature Structural and Molecular Biology | Year: 2011

The ubiquitous SecY-Sec61 complex translocates nascent secretory proteins across cellular membranes and integrates membrane proteins into lipid bilayers. Several structures of mostly detergent-solubilized Sec complexes have been reported. Here we present a single-particle cryo-EM structure of the SecYEG complex in a membrane environment, bound to a translating ribosome, at subnanometer resolution. Using the SecYEG complex reconstituted in a so-called Nanodisc, we could trace the nascent polypeptide chain from the peptidyltransferase center into the membrane. The reconstruction allowed for the identification of ribosome-lipid interactions. The rRNA helix 59 (H59) directly contacts the lipid surface and appears to modulate the membrane in immediate vicinity to the proposed lateral gate of the protein-conducting channel (PCC). On the basis of our map and molecular dynamics simulations, we present a model of a signal anchor-gated PCC in the membrane. © 2011 Nature America, Inc. All rights reserved.

Escamilla-Marvan J.E.,Institute Fisiologia Celular | Kroneck P.M.H.,University of Konstanz
Biochemistry | Year: 2010

Gluconacetobacter diazotrophicus stands out among the acetic acid bacteria, as it fixes dinitrogen and is a true endophyte. It has a. set of constitutive enzymes to oxidize ethanol and acetaldehyde which is upregulated during N 2-dependent growth. The membrane-bound alcohol dehydrogenase (ADH) is a heterodimer (subunit I ≊ 72 kDa, subunit II ≊ 44 kDa) and constitutes an important component of this organism. ADH of Ga. diazotrophicus is a typical, quinohemoprotein with one pyrroloquinoline quinone (PQQ) and four c-type cytochromes. For the first time, a [2Fe-2S] cluster has been identified by EPR spectroscopy in this type of enzyme. This finding is supported by quantitative chemical analysis, revealing 5.90 ± 0.15 Fe and 2.06 ± 0.10 acid-labile sulfurs per ADH heterodimer. The X-band EPR spectrum of ADH (as isolated in the presence of dioxygen, 20 K) showed three broad resonances at g 2.007,1.941, and 1.920 (gav 1.956), as well as an intense narrow line centered, at g = 2.0034. The latter signal, which was still detected at 100 K, was attributed to the PQQ semiquinone radical (PQQ sq). The broad resonances observed at lower temperature were assigned, to the [2Fe-2S] cluster in the one-electron reduced state. The oxidation-reduction potentials Em (pH 6.0 vs SHE) of the four c-type cytochromes were estimated, to .Em1 = -64 (±2) m V, E m2 = -8(±2)mV, & Em3 = +185 (±15) mV, and Em4 = +210(±10)mV(spectroelectrochemistry), &E mFeS = -250 (±5) mV for the [2Fe-2S] cluster, and E mPQQ = -210 (±5) mV for the PQQ/PQQH2 couple (EPR spectroscopy). We propose a model for the membrane-bound ADH of Ga. diazotrophicus showing hypothetical intra- and intermolecular electron pathways. Subunit I binds the PQQ cofactor, the [2Fe-2S] cluster, and one c-type cytochrome. Subunit II harbors three c-type cytochromes, thus providing an. efficient electron transfer route to quinones located in the cytoplasmic membrane. © 2010 American Chemical Society.

Diaz-Garcia C.M.,Institute Fisiologia Celular | Diaz-Garcia C.M.,National Autonomous University of Mexico | Sanchez-Soto C.,Institute Fisiologia Celular | Hiriart M.,Institute Fisiologia Celular
Cellular and Molecular Neurobiology | Year: 2010

Glucose-induced insulin secretion is a cardinal process in glucose homeostasis and metabolic expenditure. Uncoupling of the insulin response to glucose variations may lead to type-2 diabetes mellitus. Thus the identification of more specific drugs to facilitate the study of insulin secretion mechanisms and to develop new pharmacological agents for therapeutics is fundamental. Venomous organisms possess a great diversity of toxic molecules and some of them are neurotoxins that affect membrane excitability. This article reviews properties of those toxins affecting ion channels pivotal for insulin secretion and the usefulness of such compounds in the study of pancreatic beta-cell physiology. Here we examine the major contributions of toxinology to the understanding of the ionic phase of insulin secretion, to the determination of ion channel composition in different insulin secreting cell-line models as well as from primary cultures of different mammal species. Finally, we present a summary of the many diverse toxins affecting insulin release and a brief discussion of the potential of novel toxins in therapeutics. © 2010 Springer Science+Business Media, LLC.

Discover hidden collaborations