Peptides containing glutamine repeats as substrates for transglutaminase-catalyzed cross-linking: Relevance to diseases of the nervous system (original) (raw)
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Journal of Neurochemistry, 2004
The expansion of a polyglutamine (polyQ) domain in neuronal proteins is the molecular genetic cause of at least eight neurodegenerative diseases. Proteins with a polyQ domain that is greater than 40 Q (Q40) residues form insoluble intranuclear and cytoplasmic inclusions. Expanded polyQ proteins self-associate by non-covalent interactions and become insoluble. They can also be covalently cross-linked by tissue transglutaminase (TTG), a calcium-dependent enzyme present in cells throughout the nervous system. However, it remains unclear whether TTG cross-linking directly contributes to the insolubility of the expanded polyQ proteins. Using an in vitro solubility assay, we found TTG cross-linked Q62 monomers into high molecular weight soluble complexes in a calcium-dependent reaction. Inhibition of TTG cross-linking by primary amine substrates including putrescine and biotinylated pentylamine antagonized TTG's ability to form soluble complexes. In contrast, primary amines (histamine and lysine) that were less effective inhibitors of TTG cross-linking did not inhibit Q62 from becoming insoluble. In summary, TTG can increase the solubility of expanded polyQ proteins by catalyzing intermolecular cross-links. This demonstrates directly that TTG will reduce the ability of expanded polyQ proteins from becoming insoluble. Furthermore, the effectiveness of a primary amine substrate at inhibiting formation of insoluble inclusions may be related to their ability to inhibit intermolecular cross-linking by TTG.
Transglutaminases and neurodegeneration
Journal of Neurochemistry, 2009
Transglutaminases (TGs) are Ca 2+ -dependent enzymes that catalyze a variety of modifications of glutaminyl (Q) residues. In the brain, these modifications include the covalent attachment of a number of amine-bearing compounds, including lysyl (K) residues and polyamines, which serve to either regulate enzyme activity or attach the TG substrates to biological matrices. Aberrant TG activity is thought to contribute to Alzheimer disease, Parkinson disease, Huntington disease, and supranuclear palsy. Strategies designed to interfere with TG activity have some benefit in animal models of Huntington and Parkinson diseases. The following review summarizes the involvement of TGs in neurodegenerative diseases and discusses the possible use of selective inhibitors as therapeutic agents in these diseases.
Archives of Biochemistry and Biophysics, 1998
To investigate possible biochemical mechanisms underlying the ''toxic gain of function'' associated with polyglutamine expansions, the ability of guinea pig liver tissue transglutaminase to catalyze covalent attachments of various polyamines to polyglutamine peptides was examined. Of the polyamines tested, spermine is the most active substrate, followed by spermidine and putrescine. Formation of covalent cross links between polyglutamine peptides and polyamines yields high-M r aggregates-a process that is favored with longer polyglutamines. In the presence of tissue transglutaminase, purified glyceraldehyde-3phosphate dehydrogenase (a key glycolytic enzyme that binds tightly to the polyglutamine domains of both huntingtin and dentatorubral-pallidoluysian atrophy proteins) is covalently attached to polyglutamine peptides in vitro, resulting in the formation of high-M r aggregates. In addition, endogenous glyceraldehyde-3-phosphate dehydrogenase of a Balb-c 3T3 fibroblast cell line overexpressing human tissue transglutaminase forms cross-links with a Q 60 polypeptide added to the cell homogenate. Possibly, expansion of polyglutamine domains (thus far known to occur in the gene products associated with at least seven neurodegenerative diseases) leads to increased/aberrant tissue transglutaminase-catalyzed cross-linking reac-tions with both polyamines and susceptible proteins, such as glyceraldehyde-3-phosphate dehydrogenase. Formation of cross-linked heteropolymers may lead to deposition of high-M r protein aggregates, thereby contributing to cell death.
Proteins Containing Expanded Polyglutamine Tracts and Neurodegenerative Disease
Biochemistry, 2017
Several hereditary neurological and neuromuscular diseases are caused by an abnormal expansion of trinucleotide repeats. To date, there have been ten of these trinucleotide repeat disorders associated with an expansion of the codon CAG encoding glutamine (Q). For these polyglutamine (polyQ) diseases, there is a critical threshold length of the CAG repeat required for disease, and further expansion beyond this threshold is correlated with age of onset and symptom severity. PolyQ expansion in the translated proteins promotes their self-assembly into a variety of oligomeric and fibrillar aggregate species that accumulate into the hallmark proteinaceous inclusion bodies associated with each disease. Here, we review aggregation mechanisms of proteins with expanded polyQ-tracts, structural consequences of expanded polyQ ranging from monomers to fibrillar aggregates, the impact of protein context and post translational modifications on aggregation, and a potential role for lipids membranes in aggregation. As the pathogenic mechanisms that underlie these disorders are often classified as either a gain of toxic function or loss of normal protein function, some toxic mechanisms associated with mutant polyQ tracts will also be discussed.
Analytical Biochemistry, 2009
Trans glu ta min as es form a large fam ily of intra cel lu lar and extra cel lu lar enzymes that cat a lyze the Ca 2+ -depen dent posttrans la tional mod i fi ca tion of pro teins. These enzymes cova lently mod ify pro tein-bound glu ta mine side chains through trans a mi dation or deam i da tion reac tions. The first step in both reac tions is the acyl a tion of the active site cys teine by a pro tein-bound glu tamine res i due, result ing in the for ma tion of a thi o es ter inter me diate between trans glu ta min ase and the glu ta mine-bear ing pro tein sub strate. In trans glu ta min ase-cat a lyzed trans a mi da tion, the thio es ter inter me di ate is attacked by a nucle o philic primary amine, which is either an amine group from a small mol e cule such as putres cine or the e-amino group of pro tein-bound lysine res i dues.
FEBS letters, 1999
Several neurodegenerative diseases are caused by expansion of polyglutamine repeats in the affected proteins. In spino-cerebellar ataxia type 1 (SCA1), histidine interruptions have been reported to mitigate the pathological effects of long glutamine stretches. To understand this phenomenon, we investigated the conformational preferences of peptides containing both the uninterrupted polyglutamine stretches and those with histidine interruption(s) as seen in SCA1 normals. Our study suggests that substitution of histidines by glutamines induces a conformational change which results in decreased solubility and increased aggregation. Our findings also suggest that all the polyglutamine peptides with and without interruption(s) adopt a L L-structure and not random coil.
European Journal of Pharmacology, 2008
Alzheimer's disease, Parkinson's disease and Huntington's disease are neurodegenerative diseases, characterized by the accumulation and deposition of neurotoxic protein aggregates. The capacity of specific proteins to self-interact and form neurotoxic aggregates seems to be a common underlying mechanism leading to pathology in these neurodegenerative diseases. This process might be initiated and/or accelerated by proteins that interact with these aggregating proteins. The transglutaminase (TG) family of proteins are calcium-dependent enzymes that catalyze the formation of covalent ε-(γ-glutamyl)lysine isopeptide bonds, which can result in both intra-and intermolecular cross-links. Intramolecular cross-links might modify selfinteracting proteins, and make them more prone to aggregate. In addition, intermolecular cross-links could link self-aggregating proteins and thereby initiate and/or stimulate the aggregation process. So far, increased levels and activity of tissue transglutaminase (tTG), the best characterized member of the TG family, have been observed in many neurodegenerative diseases, and the self-interacting proteins, characteristic of Alzheimer's disease, Parkinson's disease and Huntington's disease, are known substrates of tTG. Here, we focus on the role of tTG in the initiation of the aggregation process of self-interacting proteins in these diseases, and promote the notion that tTG might be an attractive novel target for treatment of neurodegenerative diseases.
Molecular origin of polyglutamine aggregation in neurodegenerative diseases
PLoS Computational Biology, 2005
Expansion of polyglutamine (polyQ) tracts in proteins results in protein aggregation and is associated with cell death in at least nine neurodegenerative diseases. Disease age of onset is correlated with the polyQ insert length above a critical value of 35-40 glutamines. The aggregation kinetics of isolated polyQ peptides in vitro also shows a similar critical-length dependence. While recent experimental work has provided considerable insights into polyQ aggregation, the molecular mechanism of aggregation is not well understood. Here, using computer simulations of isolated polyQ peptides, we show that a mechanism of aggregation is the conformational transition in a single polyQ peptide chain from random coil to a parallel b-helix. This transition occurs selectively in peptides longer than 37 glutamines. In the b-helices observed in simulations, all residues adopt b-strand backbone dihedral angles, and the polypeptide chain coils around a central helical axis with 18.5 6 2 residues per turn. We also find that mutant polyQ peptides with proline-glycine inserts show formation of antiparallel b-hairpins in their ground state, in agreement with experiments. The lower stability of mutant b-helices explains their lower aggregation rates compared to wild type. Our results provide a molecular mechanism for polyQ-mediated aggregation. Citation: Khare SD, Ding F, Gwanmesia KN, Dokholyan NV (2005) Molecular origin of polyglutamine aggregation in neurodegenerative diseases. PLoS Comp Biol 1(3): e30.