Modulation of the in Situ Activity of Tissue Transglutaminase by Calcium and GTP

摘要: Abstract Tissue transglutaminase (tTG) is a calcium-dependent enzyme that catalyzes the posttranslational modification of proteins by transamidation specific polypeptide-bound glutamine residues. Previous in vitro studies have demonstrated transamidating activity tTG requires calcium and inhibited GTP. To investigate endogenous regulation tTG, quantitative situtransglutaminase (TG) assay was developed. Treatment human neuroblastoma SH-SY5Y cells with retinoic acid (RA) resulted significant increase levels TG activity. In contrast, basal situ did not concurrently RA-induced increased levels. However, stimulation calcium-mobilizing drug maitotoxin (MTX) increases correlated (r 2 = 0.76) examine effects GTP on activity, tiazofurin, selectively decreases levels, used. Depletion activity; however, treatment combination MTX tiazofurin significantly lessin compared alone. This raised possibility proteolysis due to because protects against trypsin. Studies selective membrane permeable calpain inhibitor indicated likely be an substrate calpain, depletion degradation after elevation intracellular also response activation muscarinic cholinergic receptors, which through inositol 1,4,5-trisphosphate generation. The results these experiments demonstrate changes regulate tTGin situ.