P4‐154: The Protein Quality Control Protein, Ubiquilin‐2, Regulates Tau Accumulation

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152960/1/alzjjalz2019063816.pd

Navigating to new frontiers in behavioral neuroscience: traditional neuropsychological tests predict human performance on a rodent-inspired radial-arm maze

We constructed an 11-arm, walk-through, human radial-arm maze (HRAM) as a translational instrument to compare existing methodology in the areas of rodent and human learning and memory research. The HRAM, utilized here, serves as an intermediary test between the classic rat radial-arm maze (RAM) and standard human neuropsychological and cognitive tests. We show that the HRAM is a useful instrument to examine working memory ability, explore the relationships between rodent and human memory and cognition models, and evaluate factors that contribute to human navigational ability. One-hundred-and-fifty-seven participants were tested on the HRAM, and scores were compared to performance on a standard cognitive battery focused on episodic memory, working memory capacity, and visuospatial ability. We found that errors on the HRAM increased as working memory demand became elevated, similar to the pattern typically seen in rodents, and that for this task, performance appears similar to Miller's classic description of a processing-inclusive human working memory capacity of 7 ± 2 items. Regression analysis revealed that measures of working memory capacity and visuospatial ability accounted for a large proportion of variance in HRAM scores, while measures of episodic memory and general intelligence did not serve as significant predictors of HRAM performance. We present the HRAM as a novel instrument for measuring navigational behavior in humans, as is traditionally done in basic science studies evaluating rodent learning and memory, thus providing a useful tool to help connect and translate between human and rodent models of cognitive functioning

SARS-CoV-2 uses CD4 to infect T helper lymphocytes

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the agent of a major global outbreak of respiratory tract disease known as Coronavirus Disease 2019 (COVID-19). SARS-CoV-2 infects mainly lungs and may cause several immune-related complications, such as lymphocytopenia and cytokine storm, which are associated with the severity of the disease and predict mortality. The mechanism by which SARS-CoV-2 infection may result in immune system dysfunction is still not fully understood. Here, we show that SARS-CoV-2 infects human CD4+ T helper cells, but not CD8+ T cells, and is present in blood and bronchoalveolar lavage T helper cells of severe COVID-19 patients. We demonstrated that SARS-CoV-2 spike glycoprotein (S) directly binds to the CD4 molecule, which in turn mediates the entry of SARS-CoV-2 in T helper cells. This leads to impaired CD4 T cell function and may cause cell death. SARS-CoV-2-infected T helper cells express higher levels of IL-10, which is associated with viral persistence and disease severity. Thus, CD4-mediated SARS-CoV-2 infection of T helper cells may contribute to a poor immune response in COVID-19 patients.</p

SARS-CoV-2 uses CD4 to infect T helper lymphocytes

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the agent of a major global outbreak of respiratory tract disease known as Coronavirus Disease 2019 (COVID-19). SARS-CoV-2 infects mainly lungs and may cause several immune-related complications, such as lymphocytopenia and cytokine storm, which are associated with the severity of the disease and predict mortality. The mechanism by which SARS-CoV-2 infection may result in immune system dysfunction is still not fully understood. Here, we show that SARS-CoV-2 infects human CD4+ T helper cells, but not CD8+ T cells, and is present in blood and bronchoalveolar lavage T helper cells of severe COVID-19 patients. We demonstrated that SARS-CoV-2 spike glycoprotein (S) directly binds to the CD4 molecule, which in turn mediates the entry of SARS-CoV-2 in T helper cells. This leads to impaired CD4 T cell function and may cause cell death. SARS-CoV-2-infected T helper cells express higher levels of IL-10, which is associated with viral persistence and disease severity. Thus, CD4-mediated SARS-CoV-2 infection of T helper cells may contribute to a poor immune response in COVID-19 patients.</p

Formation and propagation of tau oligomeric seeds

Tau misfolding and aggregation leads to the formation of neurofibrillary tangles (NFTs), which have long been considered one of the main pathological hallmarks for numerous neurodegenerative diseases known as tauopathies, including Alzheimer’s Disease (AD) and Parkinson’s Disease (PD). However, recent studies completed both in vitro and in vivo suggest that intermediate forms of tau, known as tau oligomers, between the monomeric form and NFTs are the true toxic species in disease and the best targets for anti-tau therapies. However, the exact mechanism by which the spread of pathology occurs is unknown. Evidence suggests that tau oligomers may act as templates for the misfolding of native tau, thereby seeding the spread of the toxic forms of the protein. Recently, researchers have reported the ability of tau oligomers to enter and exit cells, propagating from disease-affected regions to unaffected areas. While the mechanism by which the spreading of misfolded tau occurs has yet to be elucidated, there are a few different models which have been proposed, including cell membrane stress and pore-formation, endocytosis and exocytosis, and non-traditional secretion of protein not enclosed by a membrane. Coming to an understanding of how toxic tau species seed and spread through the brain will be crucial to finding effective treatments for neurodegenerative tauopathies

Tau oligomers: the toxic player at synapses in Alzheimer’s disease

Alzheimer’s disease (AD) is a progressive disorder in which the most noticeable symptoms are cognitive impairment and memory loss. However, the precise mechanism by which those symptoms develop remains unknown. Of note, neuronal loss occurs at sites where synaptic dysfunction is observed earlier, suggesting that altered synaptic connections precede neuronal loss. The abnormal accumulation of amyloid-β (Aβ) and tau proteins is the main histopathological feature of the disease. Several lines of evidence suggest that the small oligomeric forms of Aβ and tau may act synergistically to promote synaptic dysfunction in AD. Remarkably, tau pathology correlates better with the progression of the disease than Aβ. Recently, a growing number of studies have begun to suggest that missorting of tau protein from the axon to the dendrites is required to mediate the detrimental effects of Aβ. In this review we discuss the novel findings regarding the potential mechanisms by which tau oligomers contribute to synaptic dysfunction in AD

P3‐188: Ubiquilin‐2 Regulation Of Tau And Α‐Synuclein In Neurodegenerative Disease

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152733/1/alzjjalz2018061546.pd

UBQLN2 regulation of α- synuclein in synucleinopathies

BackgroundThe protein quality control protein ubiquilin- 2 (UBQLN2) is implicated in synucleinopathies due to its accumulation in Lewy body diseases. However, little is known about how it may interact with and clear α- synuclein (α- syn). This study aimed to define the role of UBQLN2 in handling α- syn.MethodTo evaluate whether UBQLN2 regulates α- syn, we measured levels of α- synuclein in HEK- 293 cells transiently expressing or deleted of UBQLN2. To evaluate whether UBQLN2 regulates α- syn clearance in the nervous system in vivo, we used western blot to measure total α- syn or phosphorylated human α- syn (pS129) levels in multiple transgenic mouse lines including: UBQLN2 overexpressing mice (Ub2- hi), UBQLN2 knock- out mice (Ub2- KO), and A53T α- syn mice crossed to either Ub2- hi or Ub2- KO mice. To assess changes in UBQLN2 solubility in synucleinopathies we measured levels of UBQLN2 by Western blot in PBS- soluble versus sarkosyl- soluble brain lysates from PD and LBD human brains and from A53T mouse brains.ResultIn vitro, UBQLN2 significantly decreased levels of soluble α- syn. In vivo, endogenous insoluble α- syn levels are decreased in Ub2- hi mice, while total endogenous α- syn levels are significantly increased in Ub2- KO mice. Total α- syn and pS129 levels were unchanged in A53TxUb2- hi mice versus A53T controls, but were significantly increased in A53TxUb2- KO mice. Solubility studies revealed increased insoluble UBQLN2 levels in human LBD and mouse A53T brains.ConclusionWhile UBQLN2 is known to colocalize with a- syn in disease, our results support a functional role for UBQLN2 in regulating α- syn levels. Further, we show that UBQLN2 solubility is altered in synucleinopathies. In disease, a change in UBQLN2 solubility may indicate a loss of its ability to handle a- syn, contributing to a- syn toxicity. Ongoing studies seek to elucidate the mechanism by which UBQLN2 handles, and potentially clears, α- syn.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/171612/1/alz055354.pd

Ubiquilin‐2 exacerbates tau toxicity in vivo

BackgroundUbiquilin‐2 (UBQLN2) is a protein quality control protein involved primarily in shuttling ubiquitinated substrates to the proteasome for degradation and by modulating autophagy. UBQLN2 has been implicated in neurodegenerative disease due to its accumulation in neuropathological deposits and its potential role in regulating protein dyshomeostasis common across different neurodegenerative disorders. The relationship of UBQLN2 to one of the most common aggregating proteins in disease, tau, is unknown.MethodTo evaluate whether UBQLN2 regulates tau clearance, we assessed levels of tau in human embryonic kidney‐293 cells with and without UBQLN2. To determine whether UBQLN2 acts on tau in vivo, P301S tau transgenic mice were crossed with UBQLN2 transgenic and knockout mice and brain levels of tau were assessed at 3, 6 and 9 months of age. To define changes in UBQLN2 in human disease, we measured levels of soluble and insoluble UBQLN2 in human tauopathy brain tissue.ResultCo‐expressed UBQLN2 markedly lowered levels of tau in a cellular model. Conversely, siRNA knockdown of UBQLN2 significantly elevated levels of tau. Surprisingly, a UBQLN2 mutant incapable of binding ubiquitin was more effective at lowering tau than wildtype UBQLN2, suggesting that ubiquitin‐independent pathways may allow UBQLN2 to “handle” tau. In contrast, wildtype UBQLN2 overexpression in vivo did not alter total levels of tau at 3, 6 or 9 months of age. However, UBQLN2 overexpression specifically increased phosphorylated tau while UBQLN2 knockout decreased phosphorylated tau at 9 months. Furthermore, UBQLN2 overexpression increased premature hindlimb paralysis and fatality. The possibility that UBQLN2 also undergoes alterations in disease was evidenced by the fact that UBQLN2 solubility is decreased in human brains with tau pathology.ConclusionOur findings highlight a new role for UBQLN2 in altering tau in the brain. Collectively, our results suggest that while on a rapid time scale UBQLN2 can decrease tau levels, long‐term expression of UBQLN2 in vivo exacerbates tau toxicity. Ongoing research will determine how changing UBQLN2 levels alters components of proteostasis pathways to affect tau toxicity and whether ubiquitin‐independent processes may compete with UBQLN2’s function as a ubiquitin‐proteasome shuttle factor to yield differential effects on tau toxicity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163894/1/alz046096.pd

Tau oligomers mediate α-synuclein toxicity and can be targeted by immunotherapy

Abstract Background We have evaluated the efficacy of targeting the toxic, oligomeric form of tau protein by passive immunotherapy in a mouse model of synucleinopathy. Parkinson’s disease and Lewy body dementia are two of the most common neurodegenerative disorders and are primarily characterized by the accumulation of α-synuclein in Lewy bodies. However, evidence shows that smaller, oligomeric aggregates are likely the most toxic form of the protein. Moreover, a large body of research suggests that α-synuclein interacts with tau in disease and may act in a synergistic mechanism, implicating tau oligomers as a potential therapeutic target. Methods We treated seven-month-old mice overexpressing mutated α-synuclein (A53T mice) with tau oligomer-specific monoclonal antibody (TOMA) and a control antibody and assessed both behavioral and pathological phenotypes. Results We found that A53T mice treated with TOMA were protected from cognitive and motor deficits two weeks after a single injection. Levels of toxic tau oligomers were specifically decreased in the brains of TOMA-treated mice. Tau oligomer depletion also protected against dopamine and synaptic protein loss. Conclusion These results indicate that targeting tau oligomers is beneficial for a mouse model of synucleinopathy and may be a viable therapeutic strategy for treating diseases in which tau and α-synuclein have a synergistic toxicity