Open Access
Oligomeric Bax is a component of the putative cytochrome c release channel MAC, mitochondrial apoptosis-induced channel
(American Society for Cell Biology, 2005-03-16) Dejean, Laurent M.; Martínez-Caballero, Sonia; Guo, Liang; Hughes, Cynthia; Teijido Hermida, Óscar; Ducret, Thomas; Ichas, François; Korsmeyer, Stanley J.; Antonsson, Bruno; Jonas, Elizabeth A.; Kinnally, Kathleen W.; Ciencias de la Salud; Osasun Zientziak
Bcl-2 family proteins regulate apoptosis, in part, by controlling formation of the mitochondrial apoptosis-induced channel (MAC), which is a putative cytochrome c release channel induced early in the intrinsic apoptotic pathway. This channel activity was never observed in Bcl-2-overexpressing cells. Furthermore, MAC appears when Bax translocates to mitochondria and cytochrome c is released in cells dying by intrinsic apoptosis. Bax is a component of MAC of staurosporine-treated HeLa cells because MAC activity is immunodepleted by Bax antibodies. MAC is preferentially associated with oligomeric, not monomeric, Bax. The single channel behavior of recombinant oligomeric Bax and MAC is similar. Both channel activities are modified by cytochrome c, consistent with entrance of this protein into the pore. The mean conductance of patches of mitochondria isolated after green fluorescent protein-Bax translocation is significantly higher than those from untreated cells, consistent with onset of MAC activity. In contrast, the mean conductance of patches of mitochondria indicates MAC activity is present in apoptotic cells deficient in Bax but absent in apoptotic cells deficient in both Bax and Bak. These findings indicate Bax is a component of MAC in staurosporine-treated HeLa cells and suggest Bax and Bak are functionally redundant as components of MAC.
Open Access
Regulation of Bax mitochondrial localization by Bcl-2 and Bcl-xL: keep your friends close but your enemies closer
(Elsevier, 2013) Renault, Thibaud T.; Teijido Hermida, Óscar; Antonsson, Bruno; Dejean, Laurent M.; Manon, Stéphen; Ciencias de la Salud; Osasun Zientziak
Bax-induced mitochondrial outer membrane permeabilization (MOMP) is considered as one of the key control switches of apoptosis. MOMP requires Bax relocation to and insertion into the outer mitochondrial membrane to oligomerize and form pores allowing the release of apoptogenic factors such as cytochrome c. Even if these essential steps are now well-defined, it is necessary to better understand the molecular changes underlying the switch between inactive Bax and active (pore-forming) Bax. One of the ongoing issues is to determine whether Bax mitochondrial translocation is a critical step in the control of Bax activation or if this control is carried by latter regulatory steps. In this focus article we discuss recent data suggesting that although Bcl-2 and Bcl-xL block the MOMP, they can also regulate the mitochondrial Bax content. A new model in which Bax inhibition by Bcl-xL occurs at the immediate proximity of the outer mitochondrial membrane is also discussed. This article is part of a Directed Issue entitled: Bioenergetic dysfunction, adaptation and therapy.
Open Access
Pharmacogenetics of vascular risk factors in Alzheimer's disease
(MDPI, 2018-01-03) Cacabelos, Ramón; Meyyazhagan, Arun; Carril, Juan Carlos; Cacabelos, Pablo; Teijido Hermida, Óscar; Ciencias de la Salud; Osasun Zientziak
Alzheimer's disease (AD) is a polygenic/complex disorder in which genomic, epigenomic, cerebrovascular, metabolic, and environmental factors converge to define a progressive neurodegenerative phenotype. Pharmacogenetics is a major determinant of therapeutic outcome in AD. Different categories of genes are potentially involved in the pharmacogenetic network responsible for drug efficacy and safety, including pathogenic, mechanistic, metabolic, transporter, and pleiotropic genes. However, most drugs exert pleiotropic effects that are promiscuously regulated for different gene products. Only 20% of the Caucasian population are extensive metabolizers for tetragenic haplotypes integrating CYP2D6-CYP2C19-CYP2C9-CYP3A4/5 variants. Patients harboring CYP-related poor (PM) and/or ultra-rapid (UM) geno-phenotypes display more irregular profiles in drug metabolism than extensive (EM) or intermediate (IM) metabolizers. Among 111 pentagenic (APOE-APOB-APOC3-CETP-LPL) haplotypes associated with lipid metabolism, carriers of the H26 haplotype (23-TT-CG-AG-CC) exhibit the lowest cholesterol levels, and patients with the H104 haplotype (44-CC-CC-AA-CC) are severely hypercholesterolemic. Furthermore, APOE, NOS3, ACE, AGT, and CYP variants influence the therapeutic response to hypotensive drugs in AD patients with hypertension. Consequently, the implementation of pharmacogenetic procedures may optimize therapeutics in AD patients under polypharmacy regimes for the treatment of concomitant vascular disorders.
Open Access
Pharmacogenetic considerations in the treatment of Alzheimer's disease
(Taylor & Francis, 2016) Cacabelos, Ramón; Torrellas, Clara; Teijido Hermida, Óscar; Carril, Juan Carlos ; Ciencias de la Salud; Osasun Zientziak
The practical pharmacogenetics of Alzheimer’s disease (AD) is circumscribed to acetylcholinesterase inhibitors (AChEIs) and memantine. However, pharmacogenetic procedures should be applied to novel strategies in AD therapeutics including: novel AChEIs and neurotransmitter regulators, anti-Aβ treatments, anti-tau treatments, pleiotropic products, epigenetic drugs and combination therapies. Genes involved in the pharmacogenetic network are under the influence of the epigenetic machinery which regulates gene expression transcriptionally and post-transcriptionally, configuring the fundamentals of pharmacoepigenomics. Over 60% of AD patients present concomitant pathologies demanding additional treatments which increase the likelihood of drug–drug interactions. Lipid metabolism dysfunction is a pathogenic mechanism inherent to AD neurodegeneration. The therapeutic response to hypolipidemic compounds is influenced by the APOE and CYP genotypes. The development of novel compounds and the use of combination/multifactorial treatments require the implantation of pharmacogenomic procedures for the avoidance of ADRs and the optimization of therapeutics.
Open Access
Can cloud-based tools accelerate Alzheimer's disease drug discovery?
(Taylor & Francis, 2016) Cacabelos, Ramón; Teijido Hermida, Óscar; Carril, Juan Carlos; Ciencias de la Salud; Osasun Zientziak
Open Access
Epigenetic drug discovery for alzheimer's disease
(Academic Press, 2018) Cacabelos, Ramón; Teijido Hermida, Óscar; Ciencias de la Salud; Osasun Zientziak
Alzheimer's disease (AD) is the most important neurodegenerative disorder in Western countries. Pathological phenotypes of neurodegeneration result from a combination of genomic, epigenomic, metabolic, and environmental factors, which hinders their treatment. Current FDA-approved conventional drugs are purely symptomatic but incapable to halt or, at least, delay the progression of the disease. The epigenetic approach allows the identification of key pathological targets in complex disorders that cannot be explained by conventional genetics. Many of these epigenetic targets may be detected in early asymptomatic stages of the disease. Furthermore, the reversibility and potential restoring of epigenetic aberrations, unlike genetic mutations, sited epigenetic-based therapy as a promising tool to treat those complex disorders. This chapter reviews the main potential epigenetic-based compounds that have been used for preclinical studies during the last decade and those currently submitted to clinical trials for the treatment of AD.
Open Access
Lipid dynamics and protein-lipid interactions in 2D crystals formed with the beta-barrel integral membrane protein VDAC1
(American Chemical Society, 2012) Eddy, Matthew T.; Ong, Ta-Chung; Clark, Lindsay; Teijido Hermida, Óscar; Van der Wel, Patrick C. A.; Garces, Robert; Wagner, Gerhard; Rostovtseva, Tatiana K.; Griffin, Robert G.; Ciencias de la Salud; Osasun Zientziak
We employ a combination of 13C/15N magic angle spinning (MAS) NMR and 2H NMR to study the structural and functional consequences of different membrane environments on VDAC1 and, conversely, the effect of VDAC1 on the structure of the lipid bilayer. MAS spectra reveal a well-structured VDAC1 in 2D crystals of dimyristoylphosphatidylcholine (DMPC) and diphytanoylphosphatidylcholine (DPhPC), and their temperature dependence suggests that the VDAC structure does not change conformation above and below the lipid phase transition temperature. The same data show that the N-terminus remains structured at both low and high temperatures. Importantly, functional studies based on electrophysiological measurements on these same samples show fully functional channels, even without the presence of Triton X-100 that has been found necessary for in vitro-refolded channels. 2H solid-state NMR and differential scanning calorimetry were used to investigate the dynamics and phase behavior of the lipids within the VDAC1 2D crystals. 2H NMR spectra indicate that the presence of protein in DMPC results in a broad lipid phase transition that is shifted from 19 to -27 °C and show the existence of different lipid populations, consistent with the presence of both annular and bulk lipids in the functionally and structurally homogeneous samples.
Open Access
Current state of theoretical and experimental studies of the voltage-dependent anion channel (VDAC)
(Elsevier, 2016) Noskov, Sergei Y.; Rostovtseva, Tatiana K.; Chamberlin, Adam; Teijido Hermida, Óscar; Jiang, Wei; Bezrukov, Sergey M.; Ciencias de la Salud; Osasun Zientziak
Voltage-dependent anion channel (VDAC), the major channel of the mitochondrial outer membrane provides a controlled pathway for respiratory metabolites in and out of the mitochondria. In spite of the wealth of experimental data from structural, biochemical, and biophysical investigations, the exact mechanisms governing selective ion and metabolite transport, especially the role of titratable charged residues and interactions with soluble cytosolic proteins, remain hotly debated in the field. The computational advances hold a promise to provide a much sought-after solution to many of the scientific disputes around solute and ion transport through VDAC and hence, across the mitochondrial outer membrane. In this review, we examine how Molecular Dynamics, Free Energy, and Brownian Dynamics simulations of the large β-barrel channel, VDAC, advanced our understanding. We will provide a short overview of non-conventional techniques and also discuss examples of how the modeling excursions into VDAC biophysics prospectively aid experimental efforts.
Open Access
Vacuolating megalencephalic leukoencephalopathy with subcortical cysts: functional studies of novel variants in MLC1
(Wiley, 2006-02-08) Montagna, Giorgia; Teijido Hermida, Óscar; Eymard-Pierre, Eleonore; Muraki, Koutarou; Cohen, Bruce; Loizzo, Annalivia; Grosso, Pietro; Tedeschi, Gioacchino; Palacín, Manuel; Boespflug-Tanguy, Odile; Bertini, Enrico; Santorelli, Filippo M.; Estévez, Raúl; Ciencias de la Salud; Osasun Zientziak
Nine new unrelated patients presenting vacuolating myelinopathy with subcortical cysts were identified and analyzed for variations in the MLC1 gene. We detected 12 mutations (p.Leu37fs, p.Met80Val, p.Leu83Phe, p.Pro92Ser, p.Ser93Leu, p.Ile108fs, p.Gly130Arg, p.Cys171fs, p.Glu202Lys, p.Ser269Tyr, p.Ala275Asn, and p.Leu310_311insLeu) of which nine were novel. In one patient we did not detect mutations. Using a heterologous system, three new missense variants (p.Glu202Lys, p.Ser269Tyr, and p.Ala275Asn) and a single leucine insertion (p.Leu310insLeu) - lying in a stretch of seven leucines - were functionally assayed by determining total protein levels and mutant protein expression at the plasma membrane. No correlation was observed between mutation, clinical features, and plasma membrane expression of mutant protein.
Open Access
Magic angle spinning nuclear magnetic resonance characterization of voltage-dependent anion channel gating in two-dimensional lipid crystalline bilayers
(American Chemical Society, 2014-12-29) Eddy, Matthew T.; Andreas, Loren; Teijido Hermida, Óscar; Su, Yongchao; Clark, Lindsay; Noskov, Sergei Y.; Wagner, Gerhard; Rostovtseva, Tatiana K.; Griffin, Robert G.; Ciencias de la Salud; Osasun Zientziak
The N-terminus of the voltage-dependent anion channel (VDAC) has been proposed to contain the mechanistically important gating helices that modulate channel opening and closing. In this study, we utilize magic angle spinning nuclear magnetic resonance (MAS NMR) to determine the location and structure of the N-terminus for functional channels in lipid bilayers by measuring long-range 13C–13C distances between residues in the N-terminus and other domains of VDAC reconstituted into DMPC lipid bilayers. Our structural studies show that the distance between A14 Cβ in the N-terminal helix and S193 Cβ is ∼4–6 Å. Furthermore, VDAC phosphorylation by a mitochondrial kinase at residue S193 has been claimed to delay mitochondrial cell death by causing a conformational change that closes the channel, and a VDAC-Ser193Glu mutant has been reported to show properties very similar to those of phosphorylated VDAC in a cellular context. We expressed VDAC-S193E and reconstituted it into DMPC lipid bilayers. Two-dimensional 13C–13C correlation experiments showed chemical shift perturbations for residues located in the N-terminus, indicating possible structural perturbations to that region. However, electrophysiological data recorded on VDAC-S193E showed that channel characteristics were identical to those of wild type samples, indicating that phosphorylation of S193 does not directly affect channel gating. The combination of NMR and electrophysiological results allows us to discuss the validity of proposed gating models.