An FTD-linked p62D329G polymorphism and a rare D329H variant could not be proteolyzed by caspase-8, and these noncleavable variants failed to activate mTORC1, thereby revealing the detrimental effect of these mutations.
In this work the role of p62 in energy metabolism was studied in fibroblasts from FTD patients carrying two independent pathogenic mutations in the p62 gene, and in a p62-knock-down (p62 KD) human dopaminergic neuroblastoma cell line (SH-SY5Y).
We performed a systematic review on 42 pathological studies to assess the pooled prevalence rates and density (a measure of the number of inclusions per brain region) of (phosphorylated)-TDP-43, p62 and DRP neuronal inclusions in seven brain regions and the spinal cord of 261 C9ORF72-positive patients with amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD) and ALS-FTD.
Although the frequency of the mutations is low in our series (4 of 188 patients [2%]), our results, similar to those already reported, support a direct pathogenic role of p62 in different types of FTD.
In parallel, the p62 promoter exhibited elevated oxidative damage in samples from various diseases compared to normal brain, and damage was negatively correlated with p62 expression in FTD samples.