Pathological stiffening by crosslinking glycation of titin

ABSTRACT Heterogeneous, non-enzymatic glycation chemistry triggered by sugar-derived metabolites is typical of diseases that also entail pathological stiffening of cells, such as diabetes and age-related disorders. However, the mechanisms responsible for cell stiffening and the role of glycated biomolecules remain largely unexplored. Here, we show that glycation of cardiac titin, a giant intracellular protein scaffolding contractile sarcomeres, is increased in diabetes and leads to rigidification of both the protein and cardiomyocytes. Mechanistically, glycation-induced titin stiffening results from decreased contour length and enhanced folding of otherwise structurally intact protein domains following extensive formation of intramolecular crosslinking advanced glycation end products (AGEs). These stiffening effects outweigh softening contributions by competing, non-crosslinking AGEs. In combination, our work overcomes the intrinsic chemical complexity typical of glycation to uncover crosslinking AGEs as a source of pathological stiffening of cells, which we propose contributes to tissue dysfunction in situations of glycative stress.