Earlier this year, the Garcia-Marcos laboratory reported detailed structural information describing how trimeric G proteins are activated by GBA motifs, protein segments capable of triggering G-protein signaling by a GPCR-independent mechanism. The work focused on GIV, a nucleotide exchange factor for Gαi3. Because we had previously shown that the GIV-Gαi3 interaction is required for cancer metastasis, we investigated if it could be disrupted by small molecules. The identification of such compounds would represent the first step in the development of novel anti-metastatic drugs, an urgently needed arm of current cancer therapeutic strategies.
Disrupting protein-protein interactions (PPIs) like the one established by GIV and Gαi3, however, is notoriously challenging. A significant hurdle to therapeutic development is demonstrating that a given PPI can be targeted by small molecules in the first place – i.e. they tend not to be “druggable.” To establish the druggability of our target, we combined computational approaches and wet laboratory techniques, drawing on insights gathered from our recent studies. We concluded disruption of the PPI target could indeed be achieved by small molecules and furthermore that the mode of action can be readily predicted by utilizing structural information.
The work establishes a robust pipeline for the discovery and validation of inhibitors of the GIV-Gαi3 interface and identifies a small molecule that can serve in such a role. A limitation is that the small molecule we validated was not suitable for experimentation in cancer cells or patients. The study nonetheless provides an important proof of principle for the druggability of our target, success with which could be achieved by screening larger libraries of chemical compounds. Such high-throughput screens are currently underway in our laboratory.
This work involved collaboration with the group of Francisco J. Blanco, from the CIC-BioGUNE in Spain and was published in the journal Scientific Reports.
The Gαi-GIV binding interface is a druggable protein-protein interaction. DiGiacomo V, de Opakua AI, Papakonstantinou MP, Nguyen LT, Merino N, Blanco-Canosa JB, Blanco FJ, Garcia-Marcos M. Sci Rep. 2017 Aug 17;7(1):8575. doi: 10.1038/s41598-017-08829-7. PMID: 28819150
Dr. Konstanin Kandror was appointed to the National Institutes of Health, Cellular Aspects of Diabetes and Obesity (CADO) study section and Dr. Mikel Garcia-Marcos was appointed to the Molecular and Integrative Signal Transduction study section. These appointments are made based on “their demonstrated competence and achievement in their scientific discipline as evidenced by the quality of research accomplishments, publications in scientific journals, and other significant scientific activities, achievements and honors.”
Prion diseases, or transmissible spongiform encephalopathies, comprise a group of fatal neurodegenerative disorders in humans and animals for which there are no effective treatments or cures. These diseases are caused by refolding of the cellular prion protein (PrPC) into an infectious isoform (PrPSc) that catalytically templates its abnormal conformation onto additional molecules of PrPC. A similar, prion-like process may play a role in other neurodegenerative disorders, such as Alzheimer’s and Parkinson’s diseases and tauopathies, which are due to protein misfolding and aggregation. Here, using a combination of electrophysiological, cellular, and biophysical techniques, we show that the flexible, N-terminal domain of PrPC functions as a powerful toxicity-transducing effector whose activity is tightly regulated in cis by the globular C-terminal domain. Ligands binding to the N-terminal domain abolish the spontaneous ionic currents associated with neurotoxic mutants of PrP, and the isolated N-terminal domain induces currents when expressed in the absence of the C-terminal domain. Anti-PrP antibodies targeting epitopes in the C-terminal domain induce currents, and cause degeneration of dendrites on murine hippocampal neurons, effects that entirely dependent on the effector function of the N-terminus. NMR experiments demonstrate intramolecular docking between N- and C-terminal domains of PrPC, revealing a novel auto-inhibitory mechanism that regulates the functional activity of PrPC.
We are delighted to announce the recruitment of 2 new faculty members who will be joining the Department on July 1, 2017. The search that identified these faculty members was a joint effort between the Biochemistry Department and the Genome Science Institute.
Nelson Lau, Ph.D., will be appointed as an Associate Professor. His laboratory will be located on the second floor of the K Bldg. Nelson has a long-standing involvement in the RNA field. He completed his Ph.D. at MIT in 2004 with Dr. David Bartel, a pioneer in the then nascent field of microRNAs. As part of his thesis work, he cloned the first large collection of microRNAs from C. elegans, work that was awarded the Newcomb Cleveland prize from the AAAS in 2002. From 2004-2009, Nelson was a Helen Hay Whitney Foundation fellow in the laboratory of Dr. Robert Kingston at Massachusetts General Hospital/Harvard Medical School. During his fellowship, he was the first to describe the piRNA complex from rats and mice, a discovery that was a runner-up for Science magazine’s 2006 Breakthrough of the Year. In 2009, Nelson was recruited as an Assistant Professor to the Department of Biology at Brandeis University. There, he established a vibrant and productive research program focused on regulation of the genome by transposon landscapes and the Piwi/piRNA pathway. His laboratory produced a number of important advances, including: (1) Establishment of new links between the Piwi pathway, transposon landscapes, and long non-coding RNAs; (2) Discovery of eutherian-mammal conserved genic piRNA clusters; (3) Development of new technical methods to study the RNAi pathway. Nelson’s interests complement those of Alla Grishok and Daniel Cifuentes, further adding to our department’s strengths in RNA biology. Nelson also adds two new model organisms to our department: Drosophila and Xenopus tropicalis.
Andrew Emili, Ph.D., will be a Professor, with dual appointments in the Dept. of Biochemistry and in the Department of Biology on the Charles River Campus. He will establish a Center for Network Systems Biology, which will be located on the third floor of the K Bldg. in space that is currently being renovated for this purpose. Andrew was recruited through the Provost’s Senior Faculty Hiring Initiative, aimed at attracting world-class researchers to Boston University who will bridge the two campuses. He is currently a Professor in the Donnelly Centre for Cellular and Biomolecular Research and the Department of Molecular Genetics at the University of Toronto, where he has been located since 2000. He received his Ph.D. (1997) in Molecular and Medical Genetics from the University of Toronto, and was a postdoctoral fellow (1997-2000) at the Fred Hutchison Cancer Research Center in Seattle working with John Yates. Andrew is an international leader in the analysis of protein interaction networks. He uses systems-level analysis, bioinformatics and especially proteomics to answer large-scale questions about protein-protein interaction networks in cells. Andrew’s publication list includes high profile, proteome-wide studies of protein complexes in yeast, E. coli, and human cells, and his group has documented hundreds of novel complexes linked to development and disease. Andrew’s center will synergize with the Center for Biomedical Mass Spectrometry, directed by Cathy Costello and Joe Zaia, further establishing our dept. as a leader in applications of mass spectrometry to biological problems.
Congratulations to several Biochemistry faculty who were recently awarded Dahoud Breast Cancer Pilot Awards.
Alla Grishok, PhD, Associate Professor of Biochemistry, Dafne Cardamone, PhD, Instructor, and Catherine Costello, PhD, Director of Center for Biomedical Mass Spectrometry, will study regulation of cancer-promoting Myc protein using a model metastatic breast cancer cell line. Myc binds DNA and activates a large network of genes that together transform normal cells into cancer cells. Myc activity is elevated in most human cancers and is especially relevant for Myc-driven triple (estrogen, progesterone and Her2) negative breast cancer. Dr. Grishok and colleagues will investigate new mechanisms that increase Myc protein activity: 1) adding specific sugar residues, and 2) protein truncation. New compounds that directly inhibit Myc or inhibit enzymes that activate Myc could be developed into new cancer therapies.
Xaralabos Varelas, PhD, Associate Professor of Biochemistry and Stefano Monti, PhD, Associate Professor of Medicine and Biostatistics, will study the causes of aggressive triple negative breast cancers. The team will determine how abnormal signaling networks drive gene expression changes that lead to aggressive breast cancers and then categorize subsets of aggressive breast cancers, thereby better targeting the most effective treatments based on the genes expressed in the tumor.
Mikel Garcia-Marcos has been selected as the Karin Grunebaum Cancer Research Fellow for a second year in a row. The Grunebaum Faculty Research Fellowship is a BUSM annual faculty award that provides $25,000 in total funds to a selected faculty member for a period of one year. Several Faculty members of our Department, including Bob Varelas and Valentina Perissi, have been awarded this fellowship in the past. Dr. Garcia-Marcos plans to work on developing a novel therapeutic strategy against cancer metastasis that targets an unconventional mechanism of heterotrimeric G protein activation not mediated by surface receptors (GPCRs).
Cathy Costello was recently awarded the 2017 Award for a Distinguished Contribution in Mass Spectrometry by the American Society for Mass Spectrometry. This award recognizes a singular significant achievement and was for her pioneering contributions to the development of tandem mass spectrometry of glycans and glycoconjugates. Addtional details of the award can be found on the ASMS web page. Congratulations Cathy!
The insufficient mechanistic information on metastasis has precluded the development of efficient therapeutics for it. The Gα-Interacting, Vesicle-associtated (GIV) protein is emerging as a very promising candidate to become one of the “master regulators” of metastasis and as such, its characterization may open new avenues for therapeutic intervention.
By a combination of biochemical and structural techniques, including NMR, a team of researchers have uncovered the molecular mechanism behind GIV binding and activation of a G protein. G proteins are components of the communication system the body uses to sense hormones in the bloodstream and send the corresponding messages to cells.
The results show that the mode of action of GIV differs from the well known GPCR proteins, because it binds to a different region. Molecular modelling and NMR data inform about the protein-protein interface and show that GIV binds to a cavity on the surface of the G protein. These results suggest and allosteric regulation mechanism as conformational changes in one site propagate to another distant site in the molecule.
The work has been the result of a close collaboration between the group of Mikel García-Marcos at Boston University, and the group of Francisco J Blanco at CIC bioGUNE, and has appeared in the journal Nature Communications.
The synergy between the two teams, and the participation or researchers from IRB Barcelona, Cornell University, and University of Glasgow has made it possible to uncover this novel mode of action of a G protein regulator. Multidisciplinary studies of this kind are key to characterize the complex biological processes relevant in biomedical cancer research.
Reference: Molecular mechanism of Gαi activation by non-GPCR proteins with a Gα-Binding and Activating motif. A Ibáñez de Opakua, K Parag-Sharma, V DiGiacomo, N Merino, A Leyme, A Marivin, M Villate, LT Nguyen, MA de la Cruz-Morcillo, JB Blanco-Canosa, S Ramachandran, George S Baillie, RA Cerione, FJ Blanco, M Garcia-Marcos (2017) Nature Commun 8, 13935.
The Department of Biochemistry would like to congratulate our recent graduates. Receiving a PhD in Biochemistry:Erin Bove-Fenderson, Carly Cederquist, Anthony Jay, Kshitij Khatri, Chun Shao, and Aleksander Szymaniak. Receiving a dual MD and PhD degree in biochemistry: Kelsey Derricks. Receiving a MA in Biochemistry: Wajeeha Qureshi.
Congratulations to all!
In a new “Message from the Chair” Dr. David Harris describes the exciting, new developments in the Department.