The heart is a mechanical machine that has little room for failure. Differently to pumps manufactured by men, the heart is built upon soft tissue. What are the mechanical properties of cardiac tissue and its constituent proteins sustaining the remarkable activity of the heart? How is the elasticity of the myocardium tuned to accommodate the expansion of the ventricles during diastole? How do mutations in proteins with a mechanical role trigger the development of life-threatening cardiomyopathies? Since the mechanical properties of proteins are not accessible to standard bulk biochemical techniques, our lab takes a multidisciplinary approach to try to answer all these questions. We specialize in single molecule methods using atomic force microscopy (AFM), which are able to measure the effects of mechanical forces on proteins. We produce our own polyprotein constructs using molecular biology techniques, and are equipped with FPLC instrumentation for high-quality protein purification.
You can find a list of Jorge’s publications here.
Regulation of protein elasticity by redox posttranslational modifications
Using in vitro experiments, we have recently described that posttranslational modification (PTM) of buried cysteines in the giant protein titin makes heart tissue more elastic (Cell 2014, 156:1235). We want to understand how our bodies use this novel mechanism of protein regulation to modulate the mechanical properties of the heart. With that aim, we are taking advantage of the exquisite sensitivity of mass spectrometry techniques to detect redox PTMs in heart tissue. As an independent readout of oxidation, we have also implemented in-gel detection of reduced and oxidized cysteines in titin. Once relevant redox PTMs are identified, we use single-molecule methods by AFM to determine their effect in protein elasticity. We want to explore how these mechanical PTMs are differentially present in heart diseases that alter the mechanics of the myocardium.
Conserved cysteines in the Ig domains of titin
Genotype/phenotype relations in familial cardiomyopathies
Several diseases of the heart involve deleterious changes in the mechanical properties of the myocardium. For instance, in hypertrophic cardiomyopathy the left ventricle has a hard time relaxing, which makes diastole inefficient. On the other side of the coin, in dilated cardiomyopathy the ventricle walls get thinner and the pumping activity of the heart is hampered. Interestingly, the vast majority of familial cardiomyopathies are caused by mutations in sarcomeric genes that code for proteins with mechanical roles. We are exploring the connection between dysregulation of protein mechanics and development of heart disease. Using single-molecule AFM, we measure the mechanical properties of proteins whose mutation cause cardiomyopathy. To have a fuller view on the mechanisms inducing disease phenotypes, we are setting up an extensive network of collaborators, including clinical cardiologists, companies and scientists with complementary expertise, to examine several cellular pathways that may be affected by mutations. This collaborative effort is eased by the translational focus of CNIC, which brings together basic and more-application-oriented scientists and physicians.
Proteins with mechanical roles in the sarcomere.
Development of engineered muscle-mimicking biomaterials
Integrating all we learn about the mechanics of muscle, we are engineering protein-based biomaterials that mimic the tunable elasticity of muscle. Using a directed crosslinking strategy, we are able to polymerize polyproteins into hydrogels whose stiffness can be measured in the lab using tensile testers built by us. Previous results suggest that the unfolding and refolding of the polyprotein domains within the gel are key contributors to the elasticity of the biomaterial (Macromolecular Materials and Engineering, 2015, 300, 369). Following these observations, we are developing experimental platforms that allow us to predict the stiffness of the biomaterial from the mechanical properties of the constituent polyproteins measured at the single-molecule level. This will give us valuable information about how to scale up the mechanical properties of proteins to macromolecular assemblies, let them be biomaterials or muscle fibers. We are also exploring potential translational applications of our biomaterials in tissue regeneration or implantable devices.