Hypoxic ischemia and proteasome dysfunction alter tau isoform ratio by inhibiting exon 10 splicing

• Published in: Journal of neurochemistry 2010-07, Vol.114 (1), p.160-170
• Main Authors: Suh, Jaehong, Im, Doo Soon, Moon, Gyeong Joon, Ryu, Keun Sil, de Silva, Rohan, Choi, In Sun, Lees, Andrew J, Guénette, Suzanne Y, Tanzi, Rudolph E, Gwag, Byoung Joo
• Format: Article
• Language: English
• Subjects: Alternative Splicing; Animals; Biological and medical sciences; Cells, Cultured; Cerebral Cortex - metabolism; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Exons; Hypoxia; Hypoxia-Ischemia, Brain - metabolism; ischemia; Ischemic Attack, Transient - metabolism; Male; Medical sciences; Neurology; Neurons - metabolism; Nuclear Proteins - metabolism; Phosphorylation; proteasome; proteasome endopeptidase complex; Proteasome Endopeptidase Complex - physiology; Proteasome Inhibitors; Protein Isoforms - genetics; Protein Isoforms - metabolism; Rats; Rats, Sprague-Dawley; Ribonucleic acid; RNA; RNA-Binding Proteins - metabolism; Serine-Arginine Splicing Factors; splicing; tau; tau Proteins - genetics; tau Proteins - metabolism; tra2β; Ubiquitination; Vascular diseases and vascular malformations of the nervous system
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2010.06732.x

J. Neurochem. (2010) 114, 160-170. Alternative splicing of tau exon 10 influences microtubule assembly and stability during development and in pathological processes of the central nervous system. However, the cellular events that underlie this pre-mRNA splicing remain to be delineated. In this study, we examined the possibility that ischemic injury, known to change the cellular distribution and expression of several RNA splicing factors, alters the splicing of tau exon 10. Transient occlusion of the middle cerebral artery reduced tau exon 10 inclusion in the ischemic cortical area within 12 h, resulting in the induction of three-repeat (3R) tau in cortical neurons. Ubiquitinated protein aggregates and reduced proteasome activity were also observed. Administration of proteasome inhibitors such as MG132, proteasome inhibitor I and lactacystin reduced tau exon 10 splicing in cortical cell cultures. Decreased levels of Tra2β, an RNA splicing factor responsible for tau exon 10 inclusion, were detected both in cortical cell cultures exposed to MG132 and in cerebral cortex after ischemic injury. Taken together, these findings suggest that transient focal cerebral ischemia reduces tau exon 10 splicing through a mechanism involving proteasome-ubiquitin dysfunction and down-regulation of Tra2β.