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P2‐192: Accumulation of phosphorylated TDP‐43 in neurodegenerative disorders
Author(s) -
Arai Tetsuaki,
Hasegawa Masato,
aka Takashi,
Kametani Fuyuki,
Ikeda Kenji,
Yoshsida Mari,
Hashizume Yoshio,
Beach Thomas G.,
Buratti Emanuele,
Baralle Francisco,
Morita Mitsuya,
Nakano Imaharu,
Oda Tatsuro,
Tsuchiya Kuniaki,
Akiyama Haruhiko
Publication year - 2008
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2008.05.1266
Subject(s) - phosphorylation , kinase , frontotemporal lobar degeneration , biology , amyotrophic lateral sclerosis , immunoelectron microscopy , cytoplasmic inclusion , protein phosphorylation , immunohistochemistry , microbiology and biotechnology , biochemistry , pathology , cytoplasm , protein kinase a , immunology , medicine , frontotemporal dementia , dementia , disease
loss of GRN leads to frontotemporal dementia (FTD). However, the precise mechanisms underlying GRN-mediated cell proliferation and neuronal survival are not well understood. Methods: Brains of GRN IVS0 5GC and VCP R159H mutation carriers as well as sporadic FTLD-U patients were neuropathologically and biochemically characterized to study the mechanisms of TDP-43 aggregation and caspase-3 activation by GRN haploinsufficiency. In addition, floxed-GRN knockout mice are generated for conditional targeting to gain further insights in GRN haploinsufficiency-led neuron or astrocytic degeneration. Results: A considerable heterogeneity in the relative prevalence of neuronal intranuclear (NII) or cytoplasmic (NCI) inclusions was observed within and between mutation carriers and sporadic FTLD-U patients. TDP-43 immunohistochemistry showed that the NII and NCI stained with anti-TDP-43 antibodies, but not without exceptions. A subset of inclusions was also reactive to anti-p97 and anti-p62 antibodies. Western blotting on sequential brain extracts showed that full-length TDP-43 was recoverable from early fractions while smearlike phosphorylated and possibly aggregated TDP-43 was present in the urea fraction. This fitted well with our 2D-PAGE analysis, where TDP-43 was phosphorylated at multiple distinct sites and the caspase-dependent TDP-43 cleavage led to several fragments, some of which were highly basic and potentially aggregatable. A mass spectrometric analysis of these fragments is currently being performed. Interestingly, serial solubization data also showed that phosphorylated, and possibly aggregated p62, but not p97, was present in the urea fraction. Although caspase-3 western analysis on brain lysates did not show any remarkable differences, caspase-3 immunohistochemistry showed occasional reactivity within neurons and astroglia in GRN mutation carriers although this was not significantly higher than in patients with VCP R159H or sporadic FTLD-U or with Alzheimer’s disease. Conclusions: These data suggest that caspase-3 activation can occur in FTLD-U and possibly lead to TDP-43 cleavage and aggregation. However, caspase-3 activation is also observed in other degenerative disorders and the precise mechanism by which TDP-43 would specifically aggregate in FTLD-U remains elusive. The conditional mouse models being characterized here would be important to understand the possible link between GRN haploinsufficiency and TDP-43 pathology.