About Mikel Garcia-Marcos

Manuscript accepted in PNAS


We are very happy with our recently accepted paper in Proceedings of the National Academy of Sciences (PNAS). It has been a real team effort by everybody in the lab. Below I am pasting the press release note about this publication, written by Gina DiGravio from the BU Communications Office, and the citation.


Development of New Protein May Lead to Novel Treatment Options for Cancer, Birth Defects

(Boston)—Researchers have engineered an artificial protein that may block malignant properties of cancer cells as well as correct certain birth defects. 

The findings, which appear in the journal Proceedings of the National Academy of Sciences, may lead to identifying new molecular targets suitable for therapeutic intervention.

Cells in the human body need to communicate with each other to function properly. This is accomplished by a molecular mechanism called signal transduction and its dysregulation leads to human disease. A group of molecules called G proteins act as a signaling mechanism that enables cells to change their behavior when they are activated by surface receptors.

According to the researchers, the G proteins can be activated via alternative mechanisms independent of surface receptors that also impact normal cell behavior and pathogenesis. Unfortunately, there are no efficient tools to investigate these alternative G protein activators and learn how to tackle their aberrant behavior in disease, until now.

“We have engineered an artificial protein that when expressed in cells can specifically blunt receptor-independent G protein activation and subsequent changes in cell behavior. We implemented this to block malignant properties of cancer cells and to correct birth defects associated with the aberrant dysregulation of cellular communication,” explained corresponding author Mikel Garcia-Marcos, PhD, associate professor of biochemistry at Boston University School of Medicine (BUSM). 

The researchers started with a natural G protein, removed some parts and changed some others to create a new protein that binds very tightly to a family of G protein activators while losing the ability to bind to any other known partner. Using this approach they created a protein that specifically inhibits a family of G protein activators without affecting any other component of the cellular machinery. Then they introduced it in cancer cells and observed that it can prevent their malignant properties by selectively inhibiting G protein activators. Similarly, when they  introduced the engineered protein in an experimental model, it blunted developmental defects induced by a G protein activator.

“Our findings provide the proof of principle to target a novel family of G protein regulators that are known to contribute to the development of cancer and the appearance of birth defects.  

Although the clinical implications for this discovery are indirect--since the engineered protein cannot be delivered to patients--it does represent a significant advance in the identification of a new class of molecular targets in cancer or neonatal malformations” said Garcia-Marcos.


Funding for this study was provided by the NIH, American Cancer Society and Karin Grunebaum Cancer Research Foundation.


Specific inhibition of GPCR-independent G protein signaling by a rationally engineered protein. Leyme A, Marivin A, Maziarz M, DiGiacomo V, Papakonstantinou MP, Patel PP, Blanco-Canosa JB, Walawalkar IA, Rodriguez-Davila G, Dominguez I, Garcia-Marcos M. Proc Natl Acad Sci U S A. 2017 Nov 28;114(48):E10319-E10328. doi: 10.1073/pnas.1707992114. Epub 2017 Nov 13. PMID: 29133411

Three new publications!


We have recently published three papers directly related to our efforts in elucidating and targeting molecular mechanisms of cancer metastasis. Two of them are papers describing methodological procedures related to technology we have used for drug screens and target characterization. The third one is an invited "Viewpoint" for a special issue of the journal Biochemistry. This special issue is titled "Future of Biochemistry", in which some selected "junior" investigators have been invited to make contributions. We chose to contribute with a "Viewpoint" to summarize some of our recent discoveries and express some related ideas.


Maziarz M, Garcia-Marcos M. Fluorescence polarization assays to measure interactions between Gα subunits of heterotrimeric G proteins and regulatory motifs. Methods in Cell Biology. 2017. Sept 142:133-143. PMID: 28964332.

Maziarz M, Garcia-Marcos M. Rapid kinetic BRET measurements to monitor G protein activation by GPCR and non-GPCR proteins. Methods in Cell Biology. 2017. Sept 142:145-157. PMID: 28964333.

DiGiacomo V, Marivin A, Garcia-Marcos M. When Heterotrimeric G Proteins Are Not Activated by G Protein-Coupled Receptors: Structural Insights and Evolutionary Conservation. Biochemistry. 2017. 2017 Oct 16 doi: 10.1021/acs.biochem.7b00845. [Epub ahead of print] PMID: 29035513

New publication- one step closer to new anti-metastatic agents


Earlier this year we reported detailed, atomic-level information of how GIV engages its target G protein, Gαi3, to activate it. Because we had previously shown that this interaction is required for cancer cells to become metastatic, we investigated if it could be disrupted by small chemical molecules. The identification of such molecules would represent the first step to develop novel anti-metastatic drugs. The problem is that protein-protein interactions, like the one established by GIV and Gαi3, cannot always be disrupted by small molecules, i.e., they tend to be not “druggable”.  To check the druggability of our target, we took advantage of the structural information gathered from our manuscript published earlier this year to assess if it could be disrupted by small molecules. By combining computational approaches and wet laboratory techniques, we concluded that the GIV- Gαi3 interaction can be disrupted specifically by small molecules and that the mode of action can be readily predicted based on the structural information we had previously obtained. A limitation of the work is that the small molecule that was not suitable for experimentation in cancer cells or patients. However, it provides a proof of principle for the druggability of our target, which could be achieved by screening larger libraries of chemical compounds. Such 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 (Nature publishing group).


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

Thanks for a second year award!


I am writing to express my gratitude for being selected as a Grunebaum Research Fellow for a second one-year term. I sincerely appreciate the support and I will do my best to meet the expectations.

Last year, under the support from the Karin Grunebaum Cancer research Foundation, has been a productive one for my laboratory. We have published two research manuscripts in very respected journals like Nature communications and the Journal of Biological Chemistry that advance our knowledge on the molecular mechanism that drive metastasis. Three additional manuscripts have been submitted and we hope that they will get published this coming year. We have also made very significant advance in a drug discovery campaign to identify chemical compounds to inhibit metastasis. The preliminary results from this porject were presented by Dr. DiGiacomo,  a postdoctoral fellow in my laboratory, as an oral presentation for Cancer Pharmacology Division in the anual meeting of ASPET (part of the Experimental Biology 2017 meeting in Chicago). He was one of the 3 selected topics for an oral presnetation out of >40 abstracts submitted to this Division. Now we hope to further advance this project to preclinical testing of drugs in animals, for which we are also trying to attract additional funding from Federal agencies. The support from the Karin Grunebaum Cancer Research Foundation will be critical to maintain this project fully active.

In terms of career development activities, during this last year I have been appointed as a member of the Editorial Board of the Journal of Biological Chemistry (5-year term) and also as a member of the MIST Study Section of the NIH (6-year term), which add to my ongoing service as a reviewer in the American Cancer Society.

Molecular mechanism of G protein activation by GIV, a protein that promotes metastasis.


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 nuclear magnetic resonance (NMR) spectroscopy, we 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 G protein coupled receptors (GPCRs) that typically activate G 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. Moreover, this study identifies a novel “druggable” site that could be explited to develop novel tehrapuetic agents against metastasis. This is an ongoing and very active effort of our laboratory.

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 (https://www.nature.com/articles/ncomms15163). 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.


­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.




New publication!


We are pleased to announce that our paper entitled “Membrane Recruitment of the Non-receptor Protein GIV/Girdin Is Sufficient for Activating Heterotrimeric G Protein Signaling.” has been published in the Journal of Biological Chemistry. This paper provides novel insights into the molecular mechanisms by which tumor cells sense and respond to their environment to become metastatic. GIV (aka Girdin) is a protein expressed at abnormally high levels in metastatic cancer cells. Although it was known that this protein is important to make tumor cells more invasive and metastatic, the molecular mechanisms underlying this process are still not clear. In our recently published work, we used a combination of chemogenetics, cell biology and real-time signaling biosensors to show that the critical event to activate GIV’s activity in cells is its spatial relocalization. Just by moving from one compartment to another inside the cell, GIV can trigger the signaling pathways that are hyperactive in cancer. These findings further our understanding of the molecular basis of cancer progression and set the basis to identify new vulnerabilities of metastatic cancers. This paper is the result of a joint effort of several people in our lab, but especially of an undergraduate student (Kshitij Sharma) and postdoctoral fellow (Anthony Leyme).



It is a great honor to be the new Karin Grunebaum Fellow! We will keep working hord to meet the expectations!