Chairs
Professor Mauro Dalla Serra, National Research Council of Italy, Italy
Professor Mauro Dalla Serra, National Research Council of Italy, Italy
Mauro Dalla Serra is a Senior Research Scientist of the National Research Council of Italy and Head of the Unit at Trento of the Institute of Biophysics. His scientific research interest is to investigate the structural and functional aspects of the interaction of membrane-active molecules with natural and model lipid membranes. A large portion of his work has been dedicated to protein-protein and protein-lipid interaction, to understand the mechanism of action of pore-forming proteins, that are relevant for human health. He has published more than 90 peer reviewed articles and contributed 17 chapters to multi-authored books.
13:10-13:40
Structural basis for complement membrane attack complex formation
Dr Doryen Bubeck, Imperial College London, UK
Abstract
The membrane attack complex (MAC) is a fundamental component of immune defence that drills holes in bacterial membranes and kills pathogens. MAC lesions were first identified in 1964, yet half a century later details of its structure and assembly mechanism remain undiscovered. Here electron cryo-microscopy is used to visualize the human pore complex at subnanometer resolution. The protein composition of the MAC is determined and interaction interfaces that hold the assembly together are identified. Unlike closely related pore-forming proteins, the MAC’s asymmetric pore and "split-washer" shape suggest a killing mechanism that involves not only membrane rupture, but also distortion.
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Dr Doryen Bubeck, Imperial College London, UK
Dr Doryen Bubeck, Imperial College London, UK
Doryen Bubeck received her PhD in Biophysics from Harvard University in 2005 where she used cryo-electron micrsocopy to investigate the cell entry mechanism of poliovirus. As an EMBO postdoctoral fellow and Cancer Research Institute Fellow at the University of Oxford, she continued to explore the structures of membrane proteins, focusing on the complement immune pathway. A recent highlight (Hadders & Bubeck et al., Cell Rep. 2012) is the discovery that complement components associate through a sideways alignment of their central MAC-perforin domains (MACPF). These results provide a structural framework for understanding the complex protein associations underlying activation of this innate immune effector. Doryen Bubeck is a lecturer in Structural Biology within the Department of Life Sciences and recipient of a Cancer Research UK Career Establishment Award. Her current research adopts an integrated structural approach merging cryo-electron microscopy and Xray crystallography to investigate the role of membrane proteins in host-pathogen interactions. She aims to investigate how membrane attack complex (MAC) pore formation is controlled, a process important for fighting infections and preventing complement-mediated tissue damage.
13:40-14:10
Pore formation assisted by lipids
Dr Jose Caaveiro, University of Tokyo, Japan
Abstract
Pore-forming toxins (PFT) constitute a fascinating group of proteins belonging to the molecular offensive and defensive machinery of virtually all kingdoms of life. This class of water-soluble proteins shares the remarkable ability to metamorphose in the presence of cell membranes, generating lytic pores and causing cell-damage. Actinoporins are a family of potent hemolytic toxins from sea anemone forming alpha-helical pores on cellular and model membranes.
In general, two requirements are sufficient to trigger pore-formation by actinoporins:
(i) the presence of the lipid sphingomyelin, and (ii) the segregation of the membrane on domains or lipid-rafts. Until recently, the molecular basis of pore-formation by actinoporins, and specially the specific requirement for sphingomyelin were unclear.
However, a number of recent studies have shed light into critical steps of their mechanism of action, such as binding of the toxins to the membrane, self-assembly via protein-protein interactions, and assembly of the transmembrane pore.
Collectively, the data suggests that sphingomyelin facilitates pore-formation at the binding and assembly stages, and reveal the first example of a hybrid lipid/protein pore by a PFT. The structural and thermodynamic basis of this novel architecture will be explained in detail during this presentation. Surprisingly, the entire process can be made reversible under mild experimental conditions by the careful selection of detergents, challenging current perceptions in the field of membrane-protein interactions.
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Dr Jose Caaveiro, University of Tokyo, Japan
Dr Jose Caaveiro, University of Tokyo, Japan
Dr Caaveiro graduated in the University of the Basque Country (Spain), where he studied the modulation of peptides and proteins by lipids. After a postdoctoral period in USA (MIT and Brandeis University) he then joined the University of Tokyo (since 2008). Dr. Caaveiro’s research program combines structural and thermodynamic data to address a broad range of biologically inspired phenomena. His ultimate goal is to understand the physicochemical basis underpinning biomolecular recognition at the atomic scale. Recently, Dr. Caaveiro and co-workers has revealed an unprecedented role for lipids in the pore-forming mechanism of the potent hemolytic class of actinoporins.
14:55-15:25
New insights into Bax pore formation from advanced microscopy methods
Dr Ana-Jesus Garcia-Saez, University of Tübingen, Germany
Abstract
Bax is a key player in apoptosis that mediates of the permeabilization of the outer mitochondrial membrane. Despite intense research, the underlying process remains poorly understood. By combining biophysical approaches at different scales, new insight into the molecular mechanism of Bax is provided. Electron paramagnetic resonance data shows a key conformational change in the central hairpin of Bax that is involved in pore formation. In this configuration, Bax is present as a mixture of oligomers based on dimer units, as revealed by single molecule imaging. Moreover, the nanoscale organization of Bax at mitochondria of apoptotic cells is provided by superresolution microscopy. Based on this, a new model for the molecular mechanism of Bax is proposed.
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Dr Ana-Jesus Garcia-Saez, University of Tübingen, Germany
Dr Ana-Jesus Garcia-Saez, University of Tübingen, Germany
Ana-Jesus Garcia-Saez is academic background includes Professor (W3) at the Interfaculty Institute for Biochemistry (IFIB), Universität Tübingen, Germany (October 2013), Max Planck Research Group Leader and Deutsches Krebsforschungzentrum (DKFZ) Junior Group Leader. Bioquant, Germany (2010 - current), Post-doc at the BioTec, TU Dresden, Germany (2005-2009) and PhD at the Department of Biochemistry and Molecular Biology, University of Valencia, Spain (2000-2005)
Fellowships and awards include:
• European Research Council (ERC) Starting Grant (project acronym: APOQUANT), 2012-2017.
• Max-Planck Gesellschaft Postdoctoral scholarship, Jan 2009- Dec 2009.
• Marie Curie Intra European fellowship. 6th Framework Programm, Marie Curie Actions. BIOTEC, TU Dresden (Germany). Jan 2007-Dec 2008.
• Short-term Fellowship. Federation of European Biochemical Societies. Biotechnologisches Zentrum, Technische Universität, Dresden (Germany). May-July 2005.
• Predoctoral Fellowship. Formación de Profesorado Universitario, Ministerio Español de Educación y Cultura. Faculty of Biology, University of Valencia. 1st April 2001- 31st March 2005
• Predoctoral Fellowship. Formació de Personal Investigador, Conselleria de Cultura i Educació de la Generalitat Valenciana. 1st March – 1st April 2001.
• Predoctoral Fellowship. Formación de Personal Investigador, Ministerio Español de Ciencia y Tecnología. 13th July 2001- 13th July 2001.
• Undergraduate Student Fellowship. Beca de Colaboración, Ministerio Español de Educacion y Cultura. Faculty of Biology, University of Valencia. Sept. 1999-June 2000
15:25-15:55
Regulating Bak and Bax pore formation in the mitochondrial outer membrane
Dr Ruth Kluck, The Walter and Eliza Hall Institute of Medical Research, Australia
Abstract
Two members of the Bcl-2 family, Bak and Bax, drive apoptotic cell death by changing conformation and forming oligomers that permeabilise the mitochondrial outer membrane. The two proteins are activated by BH3-only family members binding to the α2-α5 hydrophobic surface groove. Newly exposed hydrophobic regions then either “collapse” onto the membrane surface to lie in-plane, or interact to generate BH3:groove symmetric dimers. We found that in each Bak dimer the N-termini are fully solvent-exposed and mobile, allowing disulphide bonding between certain residues (e.g. V61C:V61C') to specifically interrogate how dimers associate into high order complexes. These data informed mathematical simulations that support a model in which Bak dimers interact in a random manner to form compact clusters that generate lipidic pores.
It was also found that antibodies can trigger activation of Bak and mitochondrial Bax, and do so by binding to a new activation site, the α1-α2 loop. The mechanism of antibody-mediated Bak activation involves α1 dissociation, revealed by biochemical studies and a structural model of Fab bound to Bak. Intriguingly, antibodies to the α1-α2 loop in cytosolic Bax could block its translocation to mitochondria. These data thus identify the α1-α2 loop as a new target for regulating Bak and Bax apoptotic function.
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Dr Ruth Kluck, The Walter and Eliza Hall Institute of Medical Research, Australia
Dr Ruth Kluck, The Walter and Eliza Hall Institute of Medical Research, Australia
Dr Kluck is a cell biologist who has studied apoptotic cell death since her PhD at the Queensland Institute for Medical Research, in collaboration with John Kerr who discovered apoptosis. As a postdoc at the La Jolla Institute for Allergy and Immunology (1995-2002), she made the seminal discovery that Bcl-2 proteins inhibit apoptosis by blocking mitochondrial release of cytochrome c. In 2002, she moved to the Walter and Eliza Hall Institute for Medical Research in Australia where she has focused on the regulation and function of the Bak and Bax pore-forming proteins.
16:20-16:50
Peptide-stabilized membrane pores: insights from simulations
Professor Themis Lazaridis, City College of New York, USA
Abstract
The mechanism by which amphipathic peptides permeabilize biological membranes is not well understood. Do the peptides form well-defined pores or simply dissolve the membranes in a detergent-like fashion? What is the lifetime of these pores? How do the sequence and structure of these peptides determine their permeabilizing function? Both experiment and theory face formidable challenges in obtaining detailed information on such labile structures. We have used two theoretical approaches to study peptide-induced pore formation in lipid bilayers. The first treats water and lipids implicitly and the peptide in atomistic detail. This simplified representation allows one to obtain useful insights into protein-membrane interactions. Using this approach we showed that antimicrobial peptides bind more strongly to membrane pores than to the flat membrane, consistent with the idea that they stabilize them. The second approach is fully atomistic molecular dynamics simulations, some on the 10-microsecond timescale, starting from inserted peptide aggregates. Such simulations of melittin, magainin, PGLa, alamethicin, and protegrin have revealed interesting differences between these peptides and possible explanations of the observed synergy between some of them.
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Professor Themis Lazaridis, City College of New York, USA
Professor Themis Lazaridis, City College of New York, USA
Themis Lazaridis received a Diploma in Chemical Engineering from Aristotle University in Thessaloniki, Greece in 1987. He went on to earn a Ph.D. in Chemical Engineering from the University of Delaware, USA. His Ph.D. research involved, among other topics, the development of a practical approach to calculate the entropy of hydration in water, elucidating the molecular origin of the unfavorable entropy of hydrophobic hydration. He was a postdoctoral fellow at Harvard University from 1992 to 1998, continuing to work on the statistical thermodynamics of solvation. He also worked on the energetics of protein folding and developed an implicit solvation model for proteins in solution. Since 1998 he has been a faculty member at the City College of New York. His current research interests focus on modeling protein-membrane interactions and especially the process of pore formation in membranes by antimicrobial peptides or protein toxins using implicit solvent models and all-atom simulations.