The role of the Amyloid Precursor Protein mutations and PERK-dependent signaling pathways in the pathogenesis of Alzheimer’s disease

Alzheimer’s disease (AD) is a highly complex, progressive, age-related neurodegenerative human disease entity. The genetic basis of AD is strictly connected with occurrence of mutations in Amyloid Precursor (APP) gene on chromosome 21. Molecular mechanism that leads to AD development still remains unclear. Recent data reported that it is closely correlated with Endoplasmic Reticulum (ER) stress conditions, which subsequently activate Unfolded Protein Response (UPR) signaling pathways, via the induction of protein kinase RNA-like endoplasmic reticulum kinase (PERK), as a self-protective, adaptive response to adverse stress conditions. That results in the attenuation of global protein synthesis and, on the contrary, selective translation of Activating Transcriptor Factor 4 (ATF4) and secretase β. Interestingly, under prolonged, severe ER stress UPR may switch its signal into apoptotic cell death. That ensues by ATF4-CHOP-mediated activation of a range of pro-apoptotic genes and, on the other hand, downregulation of the expression of the anti-apoptotic protein B-cell lymphoma 2 (Bcl-2) genes. Current investigations suggest that inhibitions of PERK activity may contribute to the attenuation of the deposition of toxic senile plaques in the brain tissue and, as a result, prevent degeneration of neurons and decline in cognitive abilities

Inhibition of Protein Aggregation and Endoplasmic Reticulum Stress as a Targeted Therapy for α-Synucleinopathy

α-synuclein (α-syn) is an intrinsically disordered protein abundant in the central nervous system. Physiologically, the protein regulates vesicle trafficking and neurotransmitter release in the presynaptic terminals. Pathologies related to misfolding and aggregation of α-syn are referred to as α-synucleinopathies, and they constitute a frequent cause of neurodegeneration. The most common α-synucleinopathy, Parkinson’s disease (PD), is caused by abnormal accumulation of α-syn in the dopaminergic neurons of the midbrain. This results in protein overload, activation of endoplasmic reticulum (ER) stress, and, ultimately, neural cell apoptosis and neurodegeneration. To date, the available treatment options for PD are only symptomatic and rely on dopamine replacement therapy or palliative surgery. As the prevalence of PD has skyrocketed in recent years, there is a pending issue for development of new disease-modifying strategies. These include anti-aggregative agents that target α-syn directly (gene therapy, small molecules and immunization), indirectly (modulators of ER stress, oxidative stress and clearance pathways) or combine both actions (natural compounds). Herein, we provide an overview on the characteristic features of the structure and pathogenic mechanisms of α-syn that could be targeted with novel molecular-based therapies

<i>GBA1</i> Gene Mutations in α-Synucleinopathies—Molecular Mechanisms Underlying Pathology and Their Clinical Significance

α-Synucleinopathies comprise a group of neurodegenerative diseases characterized by altered accumulation of a protein called α-synuclein inside neurons and glial cells. This aggregation leads to the formation of intraneuronal inclusions, Lewy bodies, that constitute the hallmark of α-synuclein pathology. The most prevalent α-synucleinopathies are Parkinson’s disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). To date, only symptomatic treatment is available for these disorders, hence new approaches to their therapy are needed. It has been observed that GBA1 mutations are one of the most impactful risk factors for developing α-synucleinopathies such as PD and DLB. Mutations in the GBA1 gene, which encodes a lysosomal hydrolase β-glucocerebrosidase (GCase), cause a reduction in GCase activity and impaired α-synuclein metabolism. The most abundant GBA1 gene mutations are N370S or N409S, L444P/L483P and E326K/E365K. The mechanisms by which GCase impacts α-synuclein aggregation are poorly understood and need to be further investigated. Here, we discuss some of the potential interactions between α-synuclein and GCase and show how GBA1 mutations may impact the course of the most prevalent α-synucleinopathies

Targeting NLRP3-Mediated Neuroinflammation in Alzheimer’s Disease Treatment

Alzheimer’s disease (AD) is the most common cause of dementia in the general population and, to date, constitutes a major therapeutic challenge. In the pathogenesis of AD, aggregates of amyloid β (Aβ) and neurofibrillary tangles (NFTs) containing Tau-microtubule-associated protein (tau) are known to trigger a neuroinflammatory response with subsequent formation of an inflammasome. In particular, the NOD-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is thought to play a crucial role in AD-related pathology. While the mechanisms for NLRP3 activation are not fully understood, it has been demonstrated that, after detection of protein aggregates, NLRP3 induces pro-inflammatory cytokines, such as interleukin 18 (IL-18) or interleukin 1β (IL-1β), that further potentiate AD progression. Specific inhibitors of NLRP3 that exhibit various mechanisms to attenuate the activity of NLRP3 have been tested in in vivo studies and have yielded promising results, as shown by the reduced level of tau and Aβ aggregates and diminished cognitive impairment. Herein, we would like to summarize the current state of knowledge on NLRP3 inflammasome priming, activation, and its actual role in AD pathogenesis, and to characterize the NLRP3 inhibitors that have been studied most and their impact on AD-related pathology

IRE1&alpha; Inhibitors as a Promising Therapeutic Strategy in Blood Malignancies

Synthesis, folding, and structural maturation of proteins occur in the endoplasmic reticulum (ER). Accumulation of misfolded or unfolded proteins in the ER lumen contributes to the induction of ER stress and activation of the unfolded protein response (UPR) signaling pathway. Under ER stress, the UPR tries to maintain cellular homeostasis through different pathways, including the inositol-requiring enzyme 1 alpha (IRE1&alpha;)-dependent ones. IRE1&alpha; is located in an ER membrane, and it is evolutionarily the oldest UPR sensor. Activation of IRE1&alpha; via ER stress triggers the formation of the spliced form of XBP1 (XBP1s), which has been linked to a pro-survival effect in cancer cells. The role of IRE1&alpha; is critical for blood cancer cells, and it was found that the levels of IRE1&alpha; and XBP1s are elevated in various hematological malignancies. This review paper is focused on summarizing the latest knowledge about the role of IRE1&alpha; and on the assessment of the potential utility of IRE1&alpha; inhibitors in blood cancers

Inhibition of PERK-dependent pro-adaptive signaling pathway as a promising approach for cancer treatment

Endoplasmic Reticulum (ER) is an organelle that is vital for cell growth and maintenance of homeostasis. Recent studies have reported that numerous human diseases, including cancer, are strictly connected to disruption of ER homeostasis. In order to counteract adverse intracellular conditions, cancer cells induce protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK)-dependent, pro-adaptive unfolded protein response (UPR) signaling branches. If ER stress is severe or prolonged, pro-adaptive signaling networks are insufficient, resulting in apoptotic cell death of cancer cells. The main aim: of the study was to evaluate the biological activity of a small-molecule PERK inhibitor GSK2606414 in two cancer cell lines - human neuroblastoma (SH-SY5Y) and human colorectal adenocarcinoma (HT-29) cell lines. We analyzed the level of phosphorylation of the eukaryotic initiation factor 2 (eIF2), which is the main substrate of PERK and a subsequent activator of UPR, which under long-term ER stress may evoke apoptotic death of cancer cells. Material and methods: In the study, we utilized commercially available cell lines of human colorectal adenocarcinoma HT-29 and human neuroblastoma SH-SY5Y. Cells were exposed to the tested PERK-dependent signaling inhibitor GSK2606414 in suitable culture media with addition of thapsigargin (500 nM) to induce ER stress. To identify the protein, Western blot with specific antibodies was used. Detection of immune complexes was performed using chemiluminescence. Results: We found a complete inhibition of p-eIF2α expression due to the GSK2606414 inhibitor in both cell lines, SH-SY5Y and HT-29. Conclusions: Currently available cancer treatments are insufficient and cause various side effects. It has been assumed that utilization of small-molecule inhibitors of the PERK-dependent signaling pathway, like GSK2606414, may switch the pro-adaptive branch of UPR to its pro-apoptotic branch. It is believed that the tested inhibitor GSK2606414 may become a promising treatment for many cancer types

Inhibicja zależnego od PERK proadaptacyjnego szlaku sygnałowego, jako nowe podejście w leczeniu chorób nowotworowych

Retikulum endoplazmatyczne (Endoplasmic Reticulum; ER) jest organellum komórkowym, które odgrywa istotną rolę w rozwoju komórek oraz utrzymaniu homeostazy. Ostatnie dane wskazują, iż liczne choroby człowieka, włączając raka, są ściśle związane z zaburzeniami homeostazy ER. Aby neutralizować niekorzystne warunki środowiska wewnętrznego komórki nowotworowe aktywują zależny kinazy PERK (Protein kinase R (PKR)-like Endoplasmic Reticulum kinase) proadaptacyjny szlak sygnałowy adaptacyjnej odpowiedzi na stres (Unfolded Protein Response; UPR). Gdy warunki stresu ER są ciężkie lub przedłużają się, proadaptacyjna sieć sygnałowa jest niewystarczająca, co w rezultacie prowadzi do apoptotycznej śmierci komórek nowotworowych. Głównym celem badania była ocena aktywności biologicznej niskocząsteczkowego inhibitora PERK – GSK2606414 na dwóch nowotworowych liniach komórkowych, takich jak: ludzka neuroblastoma (SH-SY5Y) oraz gruczolakorak jelita grubego (HT-29). Analizowano poziom fosforylacji eIF2α (eukaryotic initiation factor 2). Stanowi on główny substrat PERK oraz kolejny aktywator UPR, który podczas długotrwałego stresu ER może wywołać apoptotyczną śmierć komórek nowotworowych. Materiał i metody: W badaniach wykorzystano komercyjnie dostępną linię komórkową gruczolakoraka jelita grubego HT-29 oraz ludzką linię komórkową neuroblastomy SH-SY5Y. Komórki zostały poddane działaniu inhibitora kinazy PERK – GSK2606414 na odpowiedniej pożywce hodowlanej z tapsygarginą (jako czynnikiem wywołującym stres ER). W celu oceny poziomu białek użyto techniki Western blot z wykorzystaniem specyficznych przeciwciał I-rzędowych oraz II-rzędowych sprzężonych z HRP. Detekcję kompleksów immunologicznych przeprowadzano z użyciem chemiluminescencji. Wyniki: Przeprowadzone badania wykazały całkowite zahamowanie fosforylacji eIF2α przy użyciu inhibitora GSK2606414 zarówno w liniach komórkowych SH-SY5Y, jak i HT-29. Wnioski: Obecnie stosowane sposoby leczenia raka są niewystarczające i mogą wywoływać różne niekorzystne efekty uboczne. Ogólnie przyjęto, że wykorzystanie niskocząsteczkowych inhibitorów szlaków sygnałowych zależnych od PERK, jak GSK2606414, może wywołać molekularne przełączenie szlaku UPR z proadaptacyjnego na proapoptotyczny. Uważa się, że testowany inhibitor GSK2606414 może zapewnić obiecującą strategię leczenia różnych typów nowotworów

Dual role of Endoplasmic Reticulum Stress-Mediated Unfolded Protein Response Signaling Pathway in Carcinogenesis

Cancer constitutes a grave problem nowadays in view of the fact that it has become one of the main causes of death worldwide. Poor clinical prognosis is presumably due to cancer cells metabolism as tumor microenvironment is affected by oxidative stress. This event triggers adequate cellular response and thereby creates appropriate conditions for further cancer progression. Endoplasmic reticulum (ER) stress occurs when the balance between an ability of the ER to fold and transfer proteins and the degradation of the misfolded ones become distorted. Since ER is an organelle relatively sensitive to oxidative damage, aforementioned conditions swiftly cause the activation of the unfolded protein response (UPR) signaling pathway. The output of the UPR, depending on numerous factors, may vary and switch between the pro-survival and the pro-apoptotic branch, and hence it displays opposing effects in deciding the fate of the cancer cell. The role of UPR-related proteins in tumorigenesis, such as binding the immunoglobulin protein (BiP) and inositol-requiring enzyme-1&alpha; (IRE1&alpha;), activating transcription factor 6 (ATF6) or the protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), has already been specifically described so far. Nevertheless, due to the paradoxical outcomes of the UPR activation as well as gaps in current knowledge, it still needs to be further investigated. Herein we would like to elicit the actual link between neoplastic diseases and the UPR signaling pathway, considering its major branches and discussing its potential use in the development of a novel, anti-cancer, targeted therapy

Molecular Mechanisms Underlying NMDARs Dysfunction and Their Role in ADHD Pathogenesis

Attention deficit hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders, although the aetiology of ADHD is not yet understood. One proposed theory for developing ADHD is N-methyl-D-aspartate receptors (NMDARs) dysfunction. NMDARs are involved in regulating synaptic plasticity and memory function in the brain. Abnormal expression or polymorphism of some genes associated with ADHD results in NMDAR dysfunction. Correspondingly, NMDAR malfunction in animal models results in ADHD-like symptoms, such as impulsivity and hyperactivity. Currently, there are no drugs for ADHD that specifically target NMDARs. However, NMDAR-stabilizing drugs have shown promise in improving ADHD symptoms with fewer side effects than the currently most widely used psychostimulant in ADHD treatment, methylphenidate. In this review, we outline the molecular and genetic basis of NMDAR malfunction and how it affects the course of ADHD. We also present new therapeutic options related to treating ADHD by targeting NMDAR