Proteotoxicity

About: Proteotoxicity is a research topic. Over the lifetime, 549 publications have been published within this topic receiving 23151 citations.

RAGE binds preamyloid IAPP intermediates and mediates pancreatic β cell proteotoxicity

Abstract: Islet amyloidosis is characterized by the aberrant accumulation of islet amyloid polypeptide (IAPP) in pancreatic islets, resulting in β cell toxicity, which exacerbates type 2 diabetes and islet transplant failure. It is not fully clear how IAPP induces cellular stress or how IAPP-induced toxicity can be prevented or treated. We recently defined the properties of toxic IAPP species. Here, we have identified a receptor-mediated mechanism of islet amyloidosis-induced proteotoxicity. In human diabetic pancreas and in cellular and mouse models of islet amyloidosis, increased expression of the receptor for advanced glycation endproducts (RAGE) correlated with human IAPP-induced (h-IAPP-induced) β cell and islet inflammation, toxicity, and apoptosis. RAGE selectively bound toxic intermediates, but not nontoxic forms of h-IAPP, including amyloid fibrils. The isolated extracellular ligand-binding domains of soluble RAGE (sRAGE) blocked both h-IAPP toxicity and amyloid formation. Inhibition of the interaction between h-IAPP and RAGE by sRAGE, RAGE-blocking antibodies, or genetic RAGE deletion protected pancreatic islets, β cells, and smooth muscle cells from h-IAPP-induced inflammation and metabolic dysfunction. sRAGE-treated h-IAPP Tg mice were protected from amyloid deposition, loss of β cell area, β cell inflammation, stress, apoptosis, and glucose intolerance. These findings establish RAGE as a mediator of IAPP-induced toxicity and suggest that targeting the IAPP/RAGE axis is a potential strategy to mitigate this source of β cell dysfunction in metabolic disease.

Proteasome Dysfunction Associated to Oxidative Stress and Proteotoxicity in Adipocytes Compromises Insulin Sensitivity in Human Obesity

Abstract: Aims: Obesity is characterized by a low-grade systemic inflammatory state and adipose tissue (AT) dysfunction, which predispose individuals to the development of insulin resistance (IR) and metabolic disease. However, a subset of obese individuals, referred to as metabolically healthy obese (MHO) individuals, are protected from obesity-associated metabolic abnormalities. Here, we aim at identifying molecular factors and pathways in adipocytes that are responsible for the progression from the insulin-sensitive to the insulin-resistant, metabolically unhealthy obese (MUHO) phenotype. Results: Proteomic analysis of paired samples of adipocytes from subcutaneous (SC) and omental (OM) human AT revealed that both types of cells are altered in the MUHO state. Specifically, the glutathione redox cycle and other antioxidant defense systems as well as the protein-folding machinery were dysregulated and endoplasmic reticulum stress was increased in adipocytes from IR subjects. Moreover, proteasome activity ...

The Alzheimer's disease transcriptome mimics the neuroprotective signature of IGF-1 receptor-deficient neurons.

Abstract: Seminal studies using post-mortem brains of patients with Alzheimer's disease evidenced aberrant insulin-like growth factor 1 receptor (IGF1R) signalling. Addressing causality, work in animal models recently demonstrated that long-term suppression of IGF1R signalling alleviates Alzheimer's disease progression and promotes neuroprotection. However, the underlying mechanisms remain largely elusive. Here, we showed that genetically ablating IGF1R in neurons of the ageing brain efficiently protects from neuroinflammation, anxiety and memory impairments induced by intracerebroventricular injection of amyloid-β oligomers. In our mutant mice, the suppression of IGF1R signalling also invariably led to small neuronal soma size, indicative of profound changes in cellular homeodynamics. To gain insight into transcriptional signatures leading to Alzheimer's disease-relevant neuronal defence, we performed genome-wide microarray analysis on laser-dissected hippocampal CA1 after neuronal IGF1R knockout, in the presence or absence of APP/PS1 transgenes. Functional analysis comparing neurons in early-stage Alzheimer's disease with IGF1R knockout neurons revealed strongly convergent transcriptomic signatures, notably involving neurite growth, cytoskeleton organization, cellular stress response and neurotransmission. Moreover, in Alzheimer's disease neurons, a high proportion of genes responding to Alzheimer's disease showed a reversed differential expression when IGF1R was deleted. One of the genes consistently highlighted in genome-wide comparison was the neurofilament medium polypeptide Nefm. We found that NEFM accumulated in hippocampus in the presence of amyloid pathology, and decreased to control levels under IGF1R deletion, suggesting that reorganized cytoskeleton likely plays a role in neuroprotection. These findings demonstrated that significant resistance of the brain to amyloid-β can be achieved lifelong by suppressing neuronal IGF1R and identified IGF-dependent molecular pathways that coordinate an intrinsic program for neuroprotection against proteotoxicity. Our data also indicate that neuronal defences against Alzheimer's disease rely on an endogenous gene expression profile similar to the neuroprotective response activated by genetic disruption of IGF1R signalling. This study highlights neuronal IGF1R signalling as a relevant target for developing Alzheimer's disease prevention strategies.

Disrupting SUMOylation enhances transcriptional function and ameliorates polyglutamine androgen receptor–mediated disease

Abstract: Expansion of the polyglutamine (polyQ) tract within the androgen receptor (AR) causes neuromuscular degeneration in individuals with spinobulbar muscular atrophy (SBMA). PolyQ AR has diminished transcriptional function and exhibits ligand-dependent proteotoxicity, features that have both been implicated in SBMA; however, the extent to which altered AR transcriptional function contributes to pathogenesis remains controversial. Here, we sought to dissociate effects of diminished AR function from polyQ-mediated proteotoxicity by enhancing the transcriptional activity of polyQ AR. To accomplish this, we bypassed the inhibitory effect of AR SUMOylation (where SUMO indicates small ubiquitin-like modifier) by mutating conserved lysines in the polyQ AR that are sites of SUMOylation. We determined that replacement of these residues by arginine enhances polyQ AR activity as a hormone-dependent transcriptional regulator. In a murine model, disruption of polyQ AR SUMOylation rescued exercise endurance and type I muscle fiber atrophy; it also prolonged survival. These changes occurred without overt alterations in polyQ AR expression or aggregation, revealing the favorable trophic support exerted by the ligand-activated receptor. Our findings demonstrate beneficial effects of enhancing the transcriptional function of the ligand-activated polyQ AR and indicate that the SUMOylation pathway may be a potential target for therapeutic intervention in SBMA.