Thiamin mono- and pyrophosphatase activities from brain homogenate of Guamanian amyotrophic lateral sclerosis and parkinsonism-dementia patients.

Thiamin-pyrophosphatase (TPPase) and thiamin-monophosphatase (TMPase) were determined using a spectrophotometric method at various pH values (5.5, 7.5, and 9.0) in brain tissue obtained at autopsy from amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia (PD) patients from Guam and from Guamanian patients who died from other diseases (controls). TPPase separation by thin-layer polyacrylamide gel isoelectric focusing (IEF) was also performed using both gray and white matter. TPPase content, chemically determined at pH 9.0, was found to be significantly reduced in the frontal cortex of ALS and PD patients compared to controls. TMPase content, on the contrary, was unchanged. IEF analysis showed 9 clear-cut bands with TPPase activity in the pH range 5.4-7.2 and a broad band at pH 4.7-5.2. The enzymatic activity was higher in gray than in white matter. In one patient the pattern was clearly different, with two additional bands observed at pH 7.1 and 6.7, and thought to be due to genetic microheterogeneity

Activation of the Unfolded Protein Response and Proteostasis Disturbance in Parkinsonism-Dementia of Guam

Guam parkinsonism-dementia (G-PD) is a progressive and fatal neurodegenerative disorder among the native inhabitants of the Mariana Islands that manifests clinically with parkinsonism as well as dementia. Neuropathologically, G-PD is characterized by abundant neurofibrillary tangles composed of hyperphosphorylated tau, marked deposition of transactive response DNA-binding protein 43 kDa (TDP-43), and neuronal loss. The mechanisms that underlie neurodegeneration in G-PD are poorly understood. Here, we report that the unfolded protein response (UPR) is activated in G-PD brains. Specifically, we show that the endoplasmic reticulum (ER) chaperone binding immunoglobulin protein/glucose-regulated protein 78 kDa and phosphorylated (activated) ER stress sensor protein kinase RNA-like ER kinase accumulate in G-PD brains. Furthermore, proteinaceous aggregates in G-PD brains are found to contain several proteins related to the ubiquitin-proteasome system (UPS) and the autophagy pathway, two major mechanisms for intracellular protein degradation. In particular, a mutant ubiquitin (UBBthorn1), whose presence is a marker for UPS dysfunction, is shown to accumulate in G-PD brains. We demonstrate that UBBthorn1 is a potent modifier of TDP-43 aggregation and cytotoxicity in vitro. Overall, these data suggest that UPR activation and intracellular proteolytic pathways are intimately connected with the accumulation of aggregated proteins in G-PD