ROCK1 Is Associated with Alzheimer's Disease-Specific Plaques, as well as Enhances Autophagosome Formation But not Autophagic Aß Clearance.

Alzheimer's disease (AD) is the most prevalent form of late-life dementia in the population, characterized by amyloid plaque formation and increased tau deposition, which is modulated by Rho-associated coiled-coil kinase 1 (ROCK1). In this study, we further analyze whether ROCK1 regulates the metabolism of amyloid precursor protein (APP). We show that ROCK1 is colocalized with mature amyloid-ß (Aß) plaques in patients with AD, in that ROCK1 enhances the amyloidogenic pathway, and that ROCK1 mediated autophagy enhances the intracellular buildup of Aß in a cell model of AD (confirmed by increased ROCK1 and decreased Beclin 1 protein levels, with neuronal autophagosome accumulation in prefrontal cortex of AD APP/PS1 mouse model). In vitro over-expression of ROCK1 leads to a decrease in Aß secretion and an increase in the expression of autophagy-related molecules. ROCK1 interacts with Beclin1, an autophagy initiator, and enhances the intracellular accumulation of Aß. Reciprocally, overexpression of APP/Aß promotes ROCK1 expression. Our data suggest ROCK1 participates in regulating Aß secretion, APP shedding and autophagosome accumulation, and that ROCK1, rather than other kinases, is more likely to be a targetable enzyme for AD therapy.

MicroRNA-146a suppresses ROCK1 allowing hyperphosphorylation of tau in Alzheimer's disease.

MicroRNA-146a is upregulated in the brains of patients with Alzheimer's disease (AD). Here, we show that the rho-associated, coiled-coil containing protein kinase 1 (ROCK1) is a target of microRNA-146a in neural cells. Knockdown of ROCK1 mimicked the effects of microRNA-146a overexpression and induced abnormal tau phosphorylation, which was associated with inhibition of phosphorylation of the phosphatase and tensin homolog (PTEN). The ROCK1/PTEN pathway has been implicated in the neuronal hyperphosphorylation of tau that occurs in AD. To determine the function of ROCK1 in AD, brain tissue from 17 donors with low, intermediate or high probability of AD pathology were obtained and analyzed. Data showed that ROCK1 protein levels were reduced and ROCK1 colocalised with hyperphosphorylated tau in early neurofibrillary tangles. Intra-hippocampal delivery of a microRNA-146a specific inhibitor (antagomir) into 5xFAD mice showed enhanced hippocampal levels of ROCK1 protein and repressed tau hyperphosphorylation, partly restoring memory function in the 5xFAD mice. Our in vitro and in vivo results confirm that dysregulation of microRNA-146a biogenesis contributes to tau hyperphosphorylation and AD pathogenesis, and inhibition of this microRNA could be a viable novel in vivo therapy for AD.

Long noncoding RNAs in TDP-43 and FUS/TLS-related frontotemporal lobar degeneration (FTLD).

Frontotemporal lobar degeneration (FTLD) defines a spectrum of heterogeneous neurodegenerative disorders characterized by the progressive deterioration of the frontal and anterior temporal lobes of the brain. FTLD is histopathologically classified according to the presence of neuropathological protein aggregates. Two of the major pathologies, FTLD-TDP and FTLD-FUS, are characterized by the abnormal accumulation in cytoplasmic inclusions of RNA-binding proteins (RBPs) - TDP-43 and FUS/TLS, respectively. That suggests that a crucial common downstream pathway leading to cell death might involve the disruption of RNA-based mechanisms. Long noncoding RNAs have emerged as key regulators in the different layers of gene regulation. Increasing evidence suggests that long non-coding RNAs (lncRNAs) may have pivotal biological functions in the brain and, not surprisingly, they have been implicated with neurodegenerative diseases, like Alzheimer's and Parkinson's diseases. Recent studies report that FTLD/ALS-related proteins TDP-43 and FUS/TLS bind lncRNAs, and that several lncRNAs have binding sites for TDP-43 and/or FUS/TLS. These findings raise important questions about how TDP-43 and FUS/TLS pathologies can affect lncRNA-based mechanisms. One alternative is that TDP-43 and FUS/TLS regulate lncRNA transcription or transcript stability. In fact, it has been demonstrated that lncRNAs are dysregulated upon either depletion or unavailability of functional TDP-43 or FUS/TLS in a range of different models and diseases, including post-mortem samples from subjects with FTLD-TDP. The second alternative is that the binding to TDP-43 or FUS/TLS would enable lncRNAs to perform their cellular function. In this case, the unavailability of these RBPs would disrupt functional properties of lncRNAs, without necessarily altering their cellular levels. It has been experimentally demonstrated that the cellular function of some lncRNAs is strictly dependent on the direct binding to TDP-43 or FUS/TLS.

Identification of genes in toxicity pathways of trinucleotide-repeat RNA in C. elegans.

Myotonic dystrophy disorders are caused by expanded CUG repeats in noncoding regions. Here we used Caenorhabditis elegans expressing CUG repeats to identify genes that modulate the toxicity of such repeats. We identified 15 conserved genes that function as suppressors or enhancers of CUG repeat-induced toxicity and that modulate formation of nuclear foci by CUG-repeat RNA. These genes regulate CUG repeat-induced toxicity through distinct mechanisms including RNA export and clearance, thus suggesting that CUG-repeat toxicity is mediated by multiple pathways. A subset of the genes are also involved in other degenerative disorders. The nonsense-mediated mRNA decay (NMD) pathway has a conserved role in regulating CUG-repeat-RNA transcript levels and toxicity, and NMD recognition of toxic RNAs depends on 3'-untranslated-region GC-nucleotide content. Our studies suggest a broader surveillance role for NMD in which variations in this pathway influence multiple degenerative diseases.

DAF-16 employs the chromatin remodeller SWI/SNF to promote stress resistance and longevity.

Organisms are constantly challenged by stresses and privations and require adaptive responses for their survival. The forkhead box O (FOXO) transcription factor DAF-16 (hereafter referred to as DAF-16/FOXO) is a central nexus in these responses, but despite its importance little is known about how it regulates its target genes. Proteomic identification of DAF-16/FOXO-binding partners in Caenorhabditis elegans and their subsequent functional evaluation by RNA interference revealed several candidate DAF-16/FOXO cofactors, most notably the chromatin remodeller SWI/SNF. DAF-16/FOXO and SWI/SNF form a complex and globally co-localize at DAF-16/FOXO target promoters. We show that specifically for gene activation, DAF-16/FOXO depends on SWI/SNF, facilitating SWI/SNF recruitment to target promoters, to activate transcription by presumed remodelling of local chromatin. For the animal, this translates into an essential role for SWI/SNF in DAF-16/FOXO-mediated processes, in particular dauer formation, stress resistance and the promotion of longevity. Thus, we give insight into the mechanisms of DAF-16/FOXO-mediated transcriptional regulation and establish a critical link between ATP-dependent chromatin remodelling and lifespan regulation.