Detection of Transglutaminase 2 conformational changes in living cell

Transglutaminase 2 (TG2) is a ubiquitous Ca2+-dependent protein cross-linking enzyme that is implicated in a variety of biological disorders. In in vitro experiments when Ca2+ concentration was increased TG2 changed its conformation and was able to cross-link other proteins via formation of an isopeptide bond. However the mechanisms that regulate TG2 transamidation activity in cells are still unknown. In this study we have developed FRET-based method for monitoring TG2 conformation changes and, probably, cross-linking activity in living cells. Using this approach we have showed that a significant amount of TG2 within the cell is accumulated in perinuclear endosomes and has a cross-linking inactive conformation, while TG2 that is located beneath the cell membrane has a transamidation active conformation. After the induction of apoptosis cytoplasmic TG2 changed its conformation and activates while, TG2 in endosomes retained transamidation inactive conformation even at late stages of apoptosis.

► A FRET-based method for monitoring TG2 conformation changes was developed.
► TG2 conformation varies between cell compartments.
► TG2 in cross-linking inactive conformation is accumulated in perinuclear endosomes.
► TG2 conformational changes occur at the early stages of apoptosis.