The brain-specific protein TPPP/p25 in pathological protein deposits of neurodegenerative diseases

Abstract

Immunohistochemical detection of protein components of pathological inclusions is widely used for neuropathological diagnosis of neurodegenerative disorders. However, different antibodies and antigen unmasking methods may account for variability between research studies and thus may affect diagnostic accuracy. Using two different antibodies raised against either a segment (184-200 aa) or the full length of human recombinant brain-specific tubulin polymerization promoting protein TPPP/p25, we immunohistochemically screened neurodegenerative disorders, both with and without pathological alpha-synuclein structures. We tested three different epitope unmasking methods, we applied laser confocal microscopy to evaluate double immunolabelling, and we compared the amount of structures exhibiting TPPP/p25 and alpha-synuclein immunoreactivity. We demonstrate that there are a variety of staining patterns depending on the epitope retrieval method and antibody used. The antibody raised against aa 184-200 segment of TPPP/p25 is better in immunolabelling the majority of alpha-synuclein immunopositive neuronal and glial pathological profiles detectable in Parkinson's disease, diffuse Lewy-body disease, and multiple system atrophy, in addition to immunostaining some extracellular huntingtin immunoreactive structures, lipofuscin, and neuromelanin particles. In contrast, the one raised against the full-length human recombinant TPPP/p25 is more suitable to immunodetect normal oligodendrocytes. Exposition of the segment aa 184-200 of TPPP/p25 in the aggregates of pathological inclusions renders this antibody a reliable marker of all types of alpha-synucleinopathies and suggests a role for TPPP/p25 in the aggregation process of some neurodegenerative conditions.

Relocation of p25¿/tubulin polymerization promoting protein from the nucleus to the perinuclear cytoplasm in the oligodendroglia of sporadic and COQ2 mutant multiple system atrophy

“…We also confirmed the results of previous studies describing that the immunoreactivity of TPPP was markedly decreased in the peripheral processes of MSA-oligodendroglia, whereas TPPP was increased in the swollen perinuclear cytoplasm of some MSAoligodendroglia [8,11,12,27,34,35]. These observations indicate that TPPP not only relocates from the terminal processes that normally form the myelin sheath, but also translocates from the nucleus and focally accumulates in the swollen perinuclear cytoplasm.…”

Oligodendroglial Response in the Spinal Cord in TDP-43 Proteinopathy with Motor Neuron Involvement

“…This marker provides robust results in formalin-fixed paraffin-embedded tissue; its antigenicity is preserved even after prolonged fixation in routinely used fixatives and has been successfully used in previous studies [17,18,19,20,21]. Apart from neurons, oligodendrocytes are considered to be the other major cell type having pTDP-43-immunoreactive inclusions in TDP-43 proteinopathies.…”

“…In our study, we demonstrated that pTDP-43-immunoreactive inclusions colocalize with TPPP/p25, and, therefore, we confirmed that the cells containing the inclusions are indeed oligodendrocytes. The partly overlapping immunoreactivity could suggest a redistribution of cytoskeletal elements into the glial inclusions, reminiscent of the inclusions in the α-synucleinopathy called multiple system atrophy [18,19]; however, this merits further analysis. As with neurons, the majority of pTDP-43-immunoreactive inclusions in oligodendrocytes was ubiquitinated and contained p62.…”

“…Through the application of a marker of differentiated oligodendrocytes, TPPP/p25 (tubulin polymerization-promoting protein), in the present study we assess and quantify the oligodendroglial response in cases characterized by TDP-43 proteinopathy with motor neuron involvement. This marker has been used to characterize oligodendrocyte pathology in postmortem samples originating from individuals with multiple sclerosis [17], α-synucleinopathies [18,19] and temporal lobe epilepsy [20]. Additionally, our study evaluated whether pTDP-43 and p62 pathologies were associated with myelin alterations in the lateral corticospinal tract (LCS) of the spinal cord.…”

Recent developments in multiple system atrophy

“…Early myelin alterations in MSA brains have been demonstrated recently by the presence of altered myelin basic protein and p25alpha [205]. The p25alpha protein, also called tubulin polymerization promoting protein (TPPP), has been shown to colocalize with alphasynuclein-positive CGIs and to abnormally accumulate in MSA oligodendrocytes [68,87,98,168]. Transfer of p25alpha to oligodendroglial cell bodies has also been detected in early MSA, suggesting that this event causes myelin damage followed by alpha-synuclein aggregation and secondary neurodegeneration [168,205].…”