Transglutaminase-catalyzed inactivation of glyceraldehyde 3-phosphate dehydrogenase and α-ketoglutarate dehydrogenase complex by polyglutamine domains of pathological length

Several adult-onset neurodegenerative diseases are caused by genes with expanded CAG triplet repeats within their coding regions and extended polyglutamine (Q_n) domains within the expressed proteins. Generally, in clinically affected individuals n ≥ 40. Glyceraldehyde 3-phosphate dehydrogenase binds tightly to four Q_n disease proteins, but the significance of this interaction is unknown. We now report that purified glyceraldehyde 3-phosphate dehydrogenase is inactivated by tissue transglutaminase in the presence of glutathione S-transferase constructs containing a Q_n domain of pathological length (n = 62 or 81). The dehydrogenase is less strongly inhibited by tissue transglutaminase in the presence of constructs containing shorter Q_n domains (n = 0 or 10). Purified α-ketoglutarate dehydrogenase complex also is inactivated by tissue transglutaminase plus glutathione S-transferase constructs containing pathological-length Q_n domains (n = 62 or 81). The results suggest that tissue transglutaminase-catalyzed covalent linkages involving the larger poly-Q domains may disrupt cerebral energy metabolism in CAG/Q_n expansion diseases.