Transglutaminase Aggregates Huntingtin into Nonamyloidogenic Polymers, and Its Enzymatic Activity Increases in Huntington's Disease Brain Nuclei

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 96; no. 13; pp. 7388 - 7393
• Main Authors: Karpuj, Marcela V., Garren, Hideki, Slunt, Hilda, Price, Donald L., Gusella, James, Becher, Mark W., Steinman, Lawrence
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 22.06.1999; National Acad Sciences; National Academy of Sciences; The National Academy of Sciences
• Subjects: Adult; Aged; Aged, 80 and over; Aggregation; Amyloids; Biological Sciences; Brain; Brain - metabolism; Brain - ultrastructure; Cell aggregates; Cell Nucleus - metabolism; Cerebellum; Cross-Linking Reagents; Dimerization; Disease; Enzyme Activation; Enzymes; Gels; Genetics; Humans; Huntingtin Protein; Huntington Disease - metabolism; Male; Middle Aged; Nerve Tissue Proteins - metabolism; Neurology; Neurons; Nuclear Proteins - metabolism; Pathology; Peptide Fragments - metabolism; Polarized light; Polymers; Proteins; Transglutaminases - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.96.13.7388

The protein huntingtin (htt), aggregated in neuronal nuclear inclusions, is pathognomonic of Huntington's disease (HD). Constructs, translated in vitro from the N terminus of htt, containing either polyQ23 from a normal individual, or polyQ41 or polyQ67 from an HD patient, were all soluble. Transglutaminase (TGase) crosslinked these proteins, and the aggregations did not have the staining properties of amyloid. More TGase-catalyzed aggregates formed when the polyglutamine domain of htt exceeded the pathologic threshold of polyQ36. Furthermore, shorter htt constructs, containing 135 aa or fewer, formed more aggregates than did larger htt constructs. TGase activity in the HD brain was increased compared with the control, with notable increases in cell nuclei. The increased TGase activity was brain specific. In lymphoblastoid cells from HD patients, TGase activity was decreased. TGase-mediated crosslinking of htt may be involved in the formation of the nonamyloidogenic nuclear inclusions found in the HD brain. The staining properties of nuclear inclusions in the HD brain revealed that they were not amyloid.