Infection-driven activation of transglutaminase 2 boosts glucose uptake and hexosamine biosynthesis

ABSTRACTTransglutaminase 2 (TG2) is a ubiquitous enzyme with transamidating activity. We report here that the expression and activity of TG2 are enhanced in cells infected with the obligate intracellular bacteriaChlamydia trachomatis. Genetic or pharmacological inhibition of TG2 activity impair bacterial development. We show that TG2 increases glucose import by up-regulating the transcription of the glucose transporter genesGLUT-1andGLUT-3. Furthermore, TG2 activation drives one specific glucose-dependent pathway in the host, i.e. hexosamine biosynthesis. Mechanistically, we identify the glucosamine:fructose-6-phosphate amidotransferase (GFPT) among the substrates of TG2. GFPT modification by TG2 increases its enzymatic activity, resulting in higher levels of UDP-N-acetylglucosamine biosynthesis. As a consequence, TG2 activation results in increased proteinO-GlcNAcylation. The correlation between TG2 transamidating activity andO-GlcNAcylation is disrupted in infected cells because host hexosamine biosynthesis is being exploited by the bacteria, in particular to assist their division. In conclusion, our work establishes TG2 as a key player in controlling glucose-derived metabolic pathways in mammalian cells, themselves hijacked byC. trachomatisto sustain their own metabolic needs.

Defective Fibrin Crosslinking in Acute Leukemia

SummaryFibrin crosslinking was assayed in 22 patients with acute leukemia showing secondary coagulation abnormalities of variable severity. In 9 patients fibrin crosslinking was found to be normal, whereas 10 patients presented impaired polymerization of α-chains and 3 of both α- and γ-chains.Only a rough correlation was found between transamidating activity of factor XIII and the fibrin crosslinking pattern in these patients. Moreover, incomplete fibrin crosslinkage occurred at levels of factor XIII far in excess of that required for full polymerization of fibrin in “normal” plasma. This latter finding suggests that, in addition to factor XIII deficiency, other causes are responsible for thehigh rate of fibrin crosslinking impairment in acute leukemia.