DILEMMA · DecIphering nucLEar Mechanics in diabetes: a Multi-scAle perspective

DecIphering nucLEar Mechanics in diabetes: a Multi-scAle perspective

Defective molecular, cellular and tissue mechanics are emerging hallmarks for several pathologies. Clinical studies associate diabetes mellitus (DM) to stiffening in vascular, muscle and connecting tissues, determining a particular mechanical fingerprint for this disease. DM is a chronic disease characterized by hyperglycemia, leading to accumulation of irreversible damage to cellular components. At molecular level, high glucose and its by-products determine the non-enzymatic addition of sugar residues to proteins and formation of advanced glycation end products (AGEs). AGEs are clinical biomarkers of DM that correlate with heart failure risk, but the mechanism of action bridging alterations at molecular and tissue level remains elusive. An in-depth multiscale characterization of the DM mechanical landscape in vivo and in vitro is crucial to define new mechanical biomarkers that can lead to better diagnostic, prognostic, and therapeutic strategies. This requires the use of approaches that reunite multiple scales relevant for mechanobiology, from proteins to cells, tissues. AGE-mediated crosslinking of extracellular matrix (ECM) proteins is considered as the main contributor to tissue stiffness in DM. However, circulatory cells from DM patients also have impaired deformability despite a lack of ECM. Thus, changes in ECM stiffness can only partially explain the stiffening of multiple tissue types and complex physiopathological effects in DM. Alternative mechanisms suggest that direct glycation of intracellular proteins by methylglyoxal (MG), a highly reactive dicarbonyl by-product of glycolysis that increases in DM, induces posttranslational modifications (PTM) in proteins through irreversible nonenzymatic reactions with Arg and Lys residues. Resulting AGEs cause protein loss-of-function and cell dysfunction as shown for intermediate filament (IF) protein vimentin and myofilament tropomyosin.The cell nucleus is an unexpected target for AGE modifications in DM, but recent studies show that MG glycation of the transcriptional cofactors6 and histone residues compromises cell function. The effects of AGE glycation and crosslinking on cell nuclei are of high importance, since the nucleus acts as central hub in cellular mechanotransduction, both structurally and biochemically, with important implications in physiology and disease. In particular, lamins are relevant targets of AGE modifications due to their role in nuclear envelope mechano-regulation, but it is still unclear how the nuclear lamina conserves mechanical functions following AGE modifications common in DM. Here, we worked under the hypothesis that besides the ECM and the cytoskeleton, cellular nuclei can also be affected by stiffening in DM pathology, as a consequence of lamin isoforms glycation. Lamin A was studied as glycation and crosslinking target, with groundbreaking implications in DM biology due to the key role of this isoform in nuclear mechanotransduction, regulation of gene expression, transcriptional activity, and chromatin organization. Lamin glycation has multifold implications, as it could be responsible for enhanced vascular dysfunction and atherosclerosis in DM patients, or play a role in enigmatic single gene mutations causing onset of DM. The ambition of this interdisciplinary project is to decipher nuclear mechanical alterations in DM using a unique multiscale approach. Due to the unexplored connection between protein biochemistry and biophysical tools, very little is known about the mechanical landscape of the cell nucleus in DM, specifically regarding the possible modifications of lamin A proteins. The DILEMMA project proposes a unique approach that bridges the gap between advanced nanoscopy methods, cell biology and biochemical assays to generate fundamental insights of nuclear mechanics in DM at the nanoscale. We mostly focused on force transduction in lamin A proteins at the single-molecule and cellular level in the context of DM-induced glycation modifications.

Data: CORDIS, © European Union