Tissue Transglutaminase-mediated Glutamine Deamidation of β-Amyloid Peptide Increases Peptide Solubility, Whereas Enzymatic Cross-linking and Peptide Fragmentation May Serve as Molecular Triggers for Rapid Peptide Aggregation

Abstract

Tissue transglutaminase (TGase) has been implicated in a number of cellular processes and disease states, where the enzymatic actions of TGase may serve in both, cell survival and apoptosis. To date, the precise functional properties of TGase in cell survival or cell death mechanisms still remain elusive. TGasemediated cross-linking has been reported to account for the formation of insoluble lesions in conformational diseases. We report here that TGase induces intramolecular cross-linking of ␤-amyloid peptide (A␤), resulting in structural changes of monomeric A␤. Using high resolution mass spectrometry (MS) of cross-linked A␤ peptides, we observed a shift in mass, which is, presumably associated with the loss of NH 3 due to enzymatic transamidation activity and hence intramolecular peptide cross-linking. We have observed that a large population of A␤ monomers contained an 0.984 Da increase in mass at a glutamine residue, indicating that glutamine 15 serves as an indispensable substrate in TGase-mediated deamidation to glutamate 15. We provide strong analytical evidence on TGasemediated A␤ peptide dimerization, through covalent intermolecular cross-linking and hence the formation of A␤ 1-40 dimers. Our in depth analyses indicate that TGase-induced post-translational modifications of A␤ peptide may serve as an important seed for aggregation.

The blood clotting Factor XIIIa forms unique complexes with amyloid‐beta (Aβ) and colocalizes with deposited Aβ in cerebral amyloid angiopathy

“…The thioester intermediate is attacked by a nucleophilic primary amine, often the ε‐amino group of a protein‐bound lysine residue [13]. In line with this notion are our observations that the FXIIIa‐Aβ complex formation was dependent on the presence of a glutamine residue at position 15 of Aβ that also plays an important role in the tTG‐catalysed cross‐linking reactions of Aβ by serving as the glutamine donor [23]. Our data suggest that the glutamine residue at position 15 of Aβ acts as a substrate recognition site for FXIIIa.…”

Cellular Functions of Tissue Transglutaminase

“…For example, TG2-induced intramolecular cross-linking of HIV-1 aspartyl protease was shown to increase its catalytic activity (Lentini et al, 2010). Likewise, TG2-driven intramolecular cross-linking of α-synuclein (Nemes et al, 2009) and β-amyloid Aβ peptide (Schmid et al, 2011) was shown to decrease their solubility and promote their aggregation and amyloid formation, the crucial aspects of neurodegeneration in conformational diseases. The third most common form of protein cross-linking mediated by TG2 involves the generation of intermolecular isopeptide bonds that leads to the formation of covalently linked dimers, oligomers, and polymers of various substrate proteins (Fig.…”

“…This TG2-induced deamidation of crystallins is thought to contribute to age-dependent lens opacification in humans. Moreover, deamidation of Gln15 in β-amyloid peptide was shown to reduce its solubility (Schmid et al, 2011), whereas deamidation of Gln6 in substance P increased agonist potency toward its receptor (Fornelli et al, 2011), thus expanding the potential pathophysiological role of these TG2-dependent reactions (Fig. 1.3(3)).…”

Amyloid β in hereditary cerebral hemorrhage with amyloidosis-Dutch type

“…It plays an important role in the remodeling of the ECM after tissue injury and cell stress (Ientile et al, 2007). It is known that tTG mediates Aβ40 dimerization through covalent intermolecular cross-linking and thereby seeding aggregation (Schmid et al, 2011). In early stage CAA, tTG is increased in affected vessel walls and colocalizes with Aβ deposition.…”