Brain transglutaminase: in vitro crosslinking of human neurofilament proteins into insoluble polymers.

Abstract

The accumulation in aged human neurons of insoluble, high molecular weight filamentous polymers apparently linked by nondisulfide covalent bonds led us to examine human brain for the presence of transglutaminase (EC 2.3.2.13) and endogenous protein substrates for this crosslinking enzyme. We demonstrate the presence in brain of a transamidating enzyme that can covalently crosslink brain proteins into insoluble polymers in vitro by forming 'y-glutamyl-e-lysine intermolecular bridges.Brain transglutaminase is Ca2" dependent, has an electrophoretic mobility similar to that of erythrocyte transglutaminase, and is active in human postmortem brain from aged normal individuals and patients with Alzheimer disease (senile dementia). Brain neurofilament fractions incubated in the presence of transglutaminase, Ca2+, and the fluorescent amine dansylcadaverine form a fluorescent, nondisulfide-bonded insoluble polymer; this process is associated with a decrease in the amount of soluble neurofilament polypeptides in the preparation. Electron microscopy of the polymeric material reveals an extensive network ofconnecting fiaments, which can be immunostained with various neurofilament antisera. Cystamine, an inhibitor of transglutaminase, prevents the neurofilament crosslinking. Glial filaments and myelin basic protein can also serve as substrates of brain transglutaminase in vitro. Although Alzheimer disease-type paired helical filaments are not formed under the specific in vitro conditions employed, the data suggest one possible mechanism for the covalent crosslinking of filaments into insoluble polymers during human neuronal aging.

Pharmacologic transglutaminase inhibition attenuates drug‐primed liver hypertrophy but not Mallory body formation

“…Thawed tissues were dounced and sonicated in 50 mM mannitol, 2 mM Tris-HCl (pH 7.2). TG activity is based on [1,[4][5][6][7][8][9][10][11][12][13][14] …”

Isolation and characterization of brain-specific transglutaminases from rat

“…The devastating Altzheimer's disease might be derived from the crosslinking of the neurofilaments, microtubule-associated tau proteins, or amyloid β proteins (Selkoe et al, 1982;Miller and Anderton, 1986;Lorand, 1996). The gene products with polyglutamine tracts whose length is determined by the number of CAG repeats could be the putative substrates for TGase, associated with Huntington's disease, spinocerebellar ataxia type I, dentarubral-phallidoluysian atrophy, spinobulbar muscular atrophy and spinocerebeller ataxia type 3 (Cariello et al, 1996;Kahlem et al, 1996).…”

“…The transglutaminases (TGase), protein crosslinking enzymes, has been suspected to be associated with the pathogenesis of neurodegenerative diseases, notably of Altzheimer's disease, where the crosslinkings of neurofilaments (Selkoe et al, 1982), microtubule-associated tau proteins (Dudek and Johnson, 1993) or amyloid β protein (βA 4 ) (Ikura et al, 1993, Rasmussen et al, 1 9 9 4 ) were probably involved. And the recent findings that TGase-mediated formation of cytokine dimers such as interleukin 2 (Eitan and Schwartz, 1993) and midkine (Mahony et al, 1996) could affect the neuronal function suggest strongly the significant roles of the enzyme in brain.…”

Cross‐linking of a synthetic partial‐length (1–28) peptide of the Alzheimer β/A4 amyloid protein by transglutaminase

“…Selkoe et al [18,19] have characterized the transglutaminase activity in the human brain and suggested that transglutaminase is involved in the intracellular formation of helically wound intermediate filaments that make up the neurofibrillary tangles found in Alzheimer's disease. The possibility that transglutaminase is involved in the extracellular formation of the insoluble amyloid deposits has not been examined.…”