Polyamine Oxidase Is Involved in Spermidine Reduction of Transglutaminase Type 2-Catalyzed βH-Crystallins Polymerization in Calcium-Induced Experimental Cataract.
In an in vitro Ca2+-induced cataract model, the progression of opacification is paralleled by a rapid decrease of the endogenous levels of spermidine (SPD) and an increase of transglutaminase type 2 (TG2, EC 2.3.2.13)-catalyzed lens crystallins cross-linking by protein-bound N1-N8-bis(γ-glutamyl) SPD. This pattern was reversed adding exogenous SPD to the incubation resulting in a delayed loss of transparency of the rabbit lens. The present report shows evidence on the main incorporation of SPD by the catalytic activity of TG2, toward βH-crystallins and in particular to the βB2- and mostly in βB3-crystallins. The increase of endogenous SPD in the cultured rabbit lens showed the activation of a flavin adenine dinucleotide (FAD)-dependent polyamine oxidases (PAO EC 1.5.3.11). As it is known that FAD-PAO degrades the N8-terminal reactive portion of N1-mono(γ-glutamyl) SPD, the protein-bound N8-mono(γ-glutamyl) SPD was found the mainly available derivative for the potential formation of βB3-crystallins cross-links by protein-bound N1-N8-bis(γ-glutamyl)SPD. In conclusion, FAD-PAO degradation of the N8-terminal reactive residue of the crystallins bound N1-mono(γ-glutamyl)SPD together with the increased concentration of exogenous SPD, leading to saturation of glutamine residues on the substrate proteins, drastically reduces N1-N8-bis(γ-glutamyl)SPD crosslinks formation, preventing crystallins polymerization and avoiding rabbit lens opacification. The ability of SPD and MDL 72527 to modulate the activities of TG2 and FAD-PAO involved in the mechanism of lens opacification suggests a potential strategy for the prevention of senile cataract.
['Mischiati|Carlo|C|', 'Feriotto|Giordana|G|', 'Tabolacci|Claudio|C|0000-0001-5001-285X', 'Domenici|Fabio|F|0000-0001-6776-2737', 'Melino|Sonia|S|', 'Borromeo|Ilaria|I|', 'Forni|Cinzia|C|0000-0002-2617-9147', 'De Martino|Angelo|A|', 'Beninati|Simone|S|']
D000818:Animals D002386:Cataract D019204:GTP-Binding Proteins D066298:In Vitro Techniques D007908:Lens, Crystalline D000587:Oxidoreductases Acting on CH-NH Group Donors D000091345:Protein Glutamine gamma Glutamyltransferase 2 D011817:Rabbits D013095:Spermidine D011503:Transglutaminases
spermidine cataract TG2 FAD-PAO protein post-translation modification rabbit eye lens