John Koren

• Ph.D.
• Vanqua Bio

Repetitive mild traumatic brain injuries (rmTBI) are serious trauma events responsible for the development of numerous neurodegenerative disorders. A major challenge in developing diagnostics and treatments for the consequences of rmTBI is the fundamental knowledge gaps of the molecular mechanisms responsible for neurodegeneration. It is both criti...

Recent in vitro and in vivo data show that Tau‐RNA complexes contribute to neuronal dysfunction. However, whether these complexes appear in human tauopathy brains, and whether they are inherently toxic remains unknown. Clarifying the dynamics of tau‐RNA interactions and its relevance in disease would reveal critical and urgently needed information...

Background Repetitive mild traumatic brain injury (rmTBI) is a leading and severe threat to cognition that often goes undiagnosed. A major challenge in developing diagnostics and treatments for the consequences of rmTBI is the fundamental knowledge gaps that explain how TBI promotes brain dysfunction. It is both critical and urgent to understand th...

Tauopathies, including Alzheimer's disease, are characterized by progressive accumulation of hyperphosphorylated and pathologic tau protein in association with onset of cognitive and behavioral impairment. Tau pathology is also associated with increased susceptibility to seizures and epilepsy, with tau−/− mice showing seizure resistance in some epi...

Tauopathies are a group of more than twenty known disorders that involve progressive neurodegeneration, cognitive decline and pathological tau accumulation. Current therapeutic strategies provide only limited, late-stage symptomatic treatment. This is partly due to lack of understanding of the molecular mechanisms linking tau and cellular dysfuncti...

The 90 kD heat shock proteins (Hsp90) are molecular chaperones that are responsible for the folding of select proteins, many of which are directly associated with cancer progression. Consequently, inhibition of the Hsp90 protein folding machinery results in a combinatorial attack on numerous oncogenic pathways. Seventeen small-molecule inhibitors o...

Background Aberrant aggregation of misfolded microtubule‐associated protein tau ( MAPT , tau) is a hallmark of Alzheimer’s disease (AD) and other neurodegenerative tauopathies. Recently, the ATP‐dependent molecular chaperone family has been identified as a critical mediator of the pathogenic accumulation of misfolded tau. In particular, studies hav...

Tauopathies are a group of more than twenty known disorders that involve progressive neurodegeneration, cognitive decline, and pathological tau accumulation. Current therapeutic strategies provide only limited, late-stage symptomatic treatment. This is partly due to lack of understanding of the molecular mechanisms linking tau and cellular dysfunct...

Molecular chaperones are responsible for maintaining intracellular protein quality control by facilitating the conformational maturation of new proteins as well as the refolding of denatured proteins. While there are several classes of molecular chaperones in the cell, this chapter will focus solely on the small molecule modulation of Hsp90, the 90...

Optimal functioning of neuronal networks is critical to the complex cognitive processes of memory and executive function that deteriorate in Alzheimer’s disease (AD). Here we use cellular and animal models as well as human biospecimens to show that AD-related stressors mediate global disturbances in dynamic intra- and inter-neuronal networks throug...

A microsatellite expansion mutation in C9orf72 is the most common genetic cause of Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD). The expansion mutation leads to C9orf72 loss of function, RNA foci formation, and generation of five species of non-AUG RAN translated dipeptide repeat proteins (DPRs), such as poly(GA), poly(GP),...

Environmental and genetic risk factors contribute to Parkinson’s Disease (PD) pathogenesis and the associated midbrain dopamine (mDA) neuron loss. Here, we identify early PD pathogenic events by developing methodology that utilizes recent innovations in human pluripotent stem cells (hPSC) and chemical sensors of HSP90-incorporating chaperome networ...

Neuronal proteostasis is a highly regulated and crucial component of neural function. Unlike other tissues and organ, cell loss due to damage and dysfunctional signaling mechanisms is not an option for the brain. Neurons are thusly dependent on the collective cellular machinery of the molecular chaperones. Hsp70, a molecular chaperone which hydroly...

Genetic and epigenetic alterations in FK506-binding protein 5 (FKBP5) have been associated with increased risk for psychiatric disorders, including post-traumatic stress disorder (PTSD). These variants can increase the expression of FKBP5, the gene that encodes FKBP51. Excess FKBP51 promotes hypothalamic-pituitary-adrenal (HPA) axis dysregulation t...

This chapter focuses on the misbehavior of key proteins that are aberrantly misfolded or misassembled, leading to neuronal loss producing motor or cognitive impairments found in many neurological disorders, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease. These amyloid aggregates are disti...

The most common genetic cause of both Amyotrophic Lateral Sclerosis and Frontotemporal Dementia is a microsatellite expansion mutation in the 5′ UTR region of C9orf72. Expansion of the hexanucleotide repeat region of C9orf72 leads to loss of function, RNA foci, and five species of non‐AUG RAN translated dipeptide repeat proteins (GA, GP, GR, PA, &...

Gain-of-function mutations within the olfactomedin (OLF) domain of myocilin result in its toxic intracellular accumulation and hastens the onset of open-angle glaucoma. The absence of myocilin does not cause disease; therefore, strategies aimed at eliminating myocilin could lead to a successful glaucoma treatment. The endoplasmic reticulum Hsp90 pa...

Mood disorders affect nearly a quarter of the world's population. Therefore, understanding the molecular mechanisms underlying these conditions is of great importance. FK-506 binding protein 5 ( FKBP5 ) encodes the FKBP51 protein, a heat shock protein 90 kDa (Hsp90) co-chaperone, and is a risk factor for several affective disorders. FKBP51, in coor...

The ATP-dependent 90 kDa heat shock protein, Hsp90, is a major regulator of protein triage, from assisting in nascent protein folding to refolding or degrading aberrant proteins. Tau, a microtubule associated protein, aberrantly accumulates in Alzheimer's disease (AD) and other neurodegenerative diseases, deemed tauopathies. Hsp90 binds to and regu...

The heat shock protein 90 (Hsp90) family of molecular chaperones regulates protein homeostasis, folding, and degradation. The ER-resident Hsp90 isoform, glucose-regulated protein 94 (Grp94), promotes the aggregation of mutant forms of myocilin, a protein associated with primary open-angle glaucoma. While inhibition of Grp94 promotes the degradation...

Significance The accumulation of toxic tau protein, as in Alzheimer’s disease, is regulated by the 90-kDa heat shock protein (Hsp90) chaperone system. Inhibition of Hsp90 has been shown to reduce tau levels. However, Hsp90 inhibition can be problematic due to a lack of blood–brain barrier permeability and established toxicities. Here, we demonstrat...

The accumulation of amyloidogenic proteins is a pathological hallmark of neurodegenerative disorders. The aberrant accumulation of the microtubule associating protein tau (MAPT, tau) into toxic oligomers and amyloid deposits is a primary pathology in tauopathies, the most common of which is Alzheimer’s disease (AD). Intrinsically disordered protein...

Inactivation of recombinant CyP40 with cyclosporin A (CsA) after disaggregation of tau fibrils. Cyclosporin A (dashed line) or DMSO (solid line) was administered to tau fibrils in the presence (red) or absence (black/grey) of CyP40 at 16 hours. Samples were run in duplicate (n = 2). The numerical data used in figure can be found in S1 Data. (TIF)

Chymotrypsin-coupled PPIase activity assay. Curves represent No Enzyme (black), CyP40 (red), FKBP51 (blue), FKBP52 (purple) incubated with chymotrypsin (6mg/mL, pH 8.0) and substrate (Suc-AAPF-pNA, 100uM) over 300s. (One-way ANOVA, p < 0.0001, n = 2 independent preparations). The numerical data used in figure can be found in S1 Data. (TIF)

Supplemental experimental procedures. (DOCX)

Ratio-dependent CyP40 tau disaggregation. Incubations of increasing molar ratios of CyP40 to tau fibrils, as indicated, were monitored by Thioflavin T fluorescence. Samples were run in triplicate (n = 3). The numerical data used in figures can be found in S1 Data. (TIF)

CyP40 did not reduce cell viability. iHekP301LP301L cell viability was monitored using an AlamarBlue assay following CyP40 (red) or vector (black) transfection ± tau induction by tetracycline. Results are expressed relative to vector without tau induction. Samples were run in triplicate (n = 3). The numerical data used in figure can be found in S1...

Nanoparticle analysis of α-synuclein and Aβ42 fibrils after CyP40 co-incubation. (A) Nanoparticle tracking analysis size distribution of A53T α-synuclein fibrils ± CyP40. (B) Representative images of (A). (C) Nanoparticle tracking analysis size distribution of Aβ42 fibrils ± CyP40. (D) Representative images of particles of (C). (TIF)

Nanoparticle tracking analysis of CyP40. Nanoparticle tracking analysis assay of buffer (green), 7.5uM CyP40 (red), and 15uM CyP40 (orange). (TIF)

AAV9 hippocampal injections and expression. (A) AAV9-GFP (green) or AAV9-CyP40 (red) injection locations within the hippocampus are indicated. Hippocampal regions are denoted, CA1, CA2, CA3, and Dentate Gyrus (DG). (B) A representative images of AAV9-GFP and CyP40 expression in hippocampi 2 months post-injection (scale bar 200 μm). (TIF)

Expression levels of CyP40 protein from individual mouse brain lysates. Western blot analysis of CyP40 expression in AAV9-GFP and AAV9-CyP40 injected mice are compared to a standard curve generated with recombinant CyP40 protein (ng quantities indicated). Each lane represents an individual mouse. Western blot probed with anti-CyP40 antibody. (TIF)

PPIase activity assay and circular dichroism of wt and mut CyP40. (A) Coupled chymotrypsin assay of isomerase activity of wt CyP40 (red), mut CyP40 (teal), and No Enzyme (black) (n = 2 independent preparations). (B) Circular dichroism of wt CyP40 (red) and mut CyP40 (teal). The numerical data used in figure can be found in S1 Data. (TIF)

Underlying data. (XLSX)

Comparison of intrinsic disorder propensity of human and bovine CyP40 proteins. (A) Evaluating intrinsic disorder propensity of human CyP40 (UniProt ID: Q08752) by a series of per-residue disorder predictors. (B) Evaluating intrinsic disorder propensity of bovine CyP40 (UniProt ID: P26882). In these plots, disorder profiles generated by PONDR® VLXT...

Transient, multi-protein complexes are important facilitators of cellular functions. This includes the chaperome, an abundant protein family comprising chaperones, co-chaperones, adaptors, and folding enzymes—dynamic complexes of which regulate cellular homeostasis together with the protein degradation machinery1, 2, 3, 4, 5, 6. Numerous studies ha...

The emerging field of RNA nanotechnology has been used to design well-programmed, self-assembled nanostructures for applications in chemistry, biology and medicine. At the forefront of its utility in cancer is the unrestricted ability to self-assemble multiple siRNAs within a single nanostructure formulation for the RNAi screening of a wide range o...

A toxic accumulation of proteins is the hallmark pathology of several neurodegenerative disorders. Protein accumulation is regularly prevented by the network of molecular chaperone proteins, including and especially Hsp90. For reasons not yet elucidated, Hsp90 and the molecular chaperones interact with, but do not degrade, these toxic proteins resu...

Acute myeloid leukemia (AML) is a heterogeneous and fatal disease with an urgent need for improved therapeutic regimens given that most patients die from relapsed disease. Irrespective of mutation status, the development of aggressive leukemias is enabled by increasing dependence on signaling networks. We demonstrate that a hyperactive signalosome...

Background: Heat shock protein 70 family members play an important role in cancer. They are up-regulated in wide variety of tumors and the increased Hsp70 protein expression correlates with metastases, resistance to treatment and poor prognosis. Multiple mechanisms explain cancer cells dependence on Hsp70, such as inhibition of apoptosis by Hsp70,...

Background: Hsp70, a molecular chaperone responsible, in part, for the folding of nascent peptides following translation, has been implicated as a survival factor and a poor prognostic marker in cancer cells. These pro-cancer mechanisms originate in the ability of Hsp70 to preserve and maintain oncogenic and transformative proteins responsible for...

The kinase PRKD2 is a crucial regulator of tumor cell-endothelial cell communication in gastrointestinal tumors and glioblastomas, but its mechanistic contributions to malignant development are not understood. Here we report that the oncogenic chaperone HSP90 binds to and stabilizes PRKD2 in human cancer cells. Pharmacologic inhibition of HSP90 wit...

Heat shock protein 70 (Hsp70) is a family of proteins with key roles in regulating malignancy. Cancer cells rely on Hsp70 to inhibit apoptosis, regulate senescence and autophagy, and maintain the stability of numerous onco-proteins. Despite these important biological functions in cancer, robust chemical tools that enable the analysis of the Hsp70-r...

Introduction: Heat shock protein 90 (HSP90) serves as a critical facilitator for oncogene addiction. There has been augmenting enthusiasm in pursuing HSP90 as an anticancer strategy. In fact, since the initial serendipitous discovery that geldanamycin (GM) inhibits HSP90, the field has rapidly moved from proof-of-concept clinical studies with GM d...

Protein folding, protein degradation, and protein stability are regulated by the molecular chaperones. Under pathogenic conditions, aberrant proteins can be dysfunctional, unregulated, or pathogenically mutated. These aberrant proteins are triaged by the chaperone network for the maintenance of cellular homeostasis. These species, called chaperone...

Constitutive expression of HSP90 in normal cells is required for its evolutionarily conserved housekeeping function of folding and translocating cellular proteins to their proper cellular compartment. Under the stress of malignant transformation, cellular proteins and networks become perturbed requiring specific maintenance by a stress-modified HSP...

Research on the FKBP5 gene and FKBP51 protein has more than doubled since the discovery that polymorphisms in this gene could alter treatment outcomes and depressive behavior in humans. This coincided with other data suggesting that the stress hormone axis contributes to the development of numerous mental illnesses. As a result, FKBP51 now lies at...

Background: The microtubule-associated protein tau accumulates in neurodegenerative diseases known as tauopathies, the most common being Alzheimer's disease. One way to treat these disorders may be to reduce abnormal tau levels through chaperone manipulation, thus subverting synaptic plasticity defects caused by tau's toxic accretion. Methods: T...

Imbalanced protein load within cells is a critical aspect for most diseases of aging. In particular, the accumulation of proteins into neurotoxic aggregates is a common thread for a host of neurodegenerative diseases. Recent work demonstrates that age-related changes to the cellular chaperone repertoire contributes to abnormal buildup of the microt...

Maintenance of cellular homeostasis is regulated by the molecular chaperones. Under pathogenic conditions, aberrant proteins are triaged by the chaperone network. These aberrant proteins, known as "clients," have major roles in the pathogenesis of numerous neurological disorders, including tau in Alzheimer's disease, α-synuclein and LRRK2 in Parkin...

Clearance of misfolded proteins in the endoplasmic reticulum (ER) is traditionally handled by ER-associated degradation, a process that requires retro-translocation and ubiquitination mediated by a lumenal chaperone network. Here we investigated whether the secreted, glaucoma-associated protein myocilin was processed by this pathway. Myocilin is ty...

[This corrects the article on p. e35566 in vol. 7.].

MKT-077, a rhodacyanine dye, was shown to produce cancer specific cell death. However, complications prevented the use of this compound beyond clinical trials. Here we describe YM-1, a derivative of MKT-077. We found that YM-1 was more cytotoxic and localized differently than MKT-077. YM-1 demonstrated this cytotoxicity across multiple cancer cell...

The heat shock protein (Hsp) family is an evolutionarily conserved system that is charged with preventing unfolded or misfolded proteins in the cell from aggregating. In Alzheimer's disease, extracellular accumulation of the amyloid β peptide (Aβ) and intracellular aggregation of the microtubule associated protein tau may result from mechanisms inv...

Tau is a microtubule-associated protein that accumulates in at least 15 different neurodegenerative disorders, which are collectively referred to as tauopathies. In these diseases, tau is often hyperphosphorylated and found in aggregates, including paired helical filaments, neurofibrillary tangles and other abnormal oligomers. Tau aggregates are as...

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL A prevalent problem in the use of chemotherapies for the treatment of human cancers is the potential for the development of resistance. While the exact nature of the mechanisms involved in resistance development vary based on cancer type as well as the nature of the therapeut...

https://deepblue.lib.umich.edu/bitstream/2027.42/152875/1/alzjjalz2011051565.pdf

Impaired nutrient delivery to the brain due to decreased blood flow contributes to cognitive decline and dementia in Alzheimer's disease (AD). Considering this, many studies have suggested that neuroprotective agents like those used in stroke could prevent AD onset or progression by promoting cell survival. However, research in the past decade sugg...

The Hsp90-associated cis-trans peptidyl-prolyl isomerase--FK506 binding protein 51 (FKBP51)--was recently found to co-localize with the microtubule (MT)-associated protein tau in neurons and physically interact with tau in brain tissues from humans who died from Alzheimer's disease (AD). Tau pathologically aggregates in neurons, a process that is c...

The microtubule-associated protein tau, which becomes hyperphosphorylated and pathologically aggregates in a number of these diseases, is extremely sensitive to manipulations of chaperone signaling. For example, Hsp90 inhibitors can reduce the levels of tau in transgenic mouse models of tauopathy. Because of this, we hypothesized that a number of H...

Target-based drug discovery for Alzheimer's disease (AD) centered on modulation of the amyloid β peptide has met with limited success. Therefore, recent efforts have focused on targeting the microtubule-associated protein tau. Tau pathologically accumulates in more than 15 neurodegenerative diseases and is most closely linked with postsymptomatic p...

Supplementary data on the administration of methylene blue in rTg4510 mice. Additional data contains information on the effect of chronic dosing of MB on behavior and statistical comparisons between parenchymal drug concentration, gender, and weight.

It has traditionally been thought that the pathological accumulation of tau in Alzheimer's disease and other tauopathies facilitates neurodegeneration, which in turn leads to cognitive impairment. However, recent evidence suggests that tau tangles are not the entity responsible for memory loss, rather it is an intermediate tau species that disrupts...

Molecular chaperones regulate the aggregation of a number of proteins that pathologically misfold and accumulate in neurodegenerative diseases. Identifying ways to manipulate these proteins in disease models is an area of intense investigation; however, the translation of these results to the mammalian brain has progressed more slowly. In this stud...

A major question for gene therapy in brain concerns methods to administer therapeutic genes in a uniform manner over major portions of the brain. A second question in neuroimmunology concerns the extent to which monocytes migrate to the CNS in degenerative disorders. Here we show that CD11b+ cells (largely monocytes) isolated from the bone marrow o...

According to a recent hypothesis, neurodegenerative diseases are age-related diseases of specific brain regions that have developed relatively recently in evolutionary time in Homo sapiens (Ghika, 2008). Alzheimer's disease was the first to be thought of as a disease of “phylogenic regression” (Rapoport 1988, 1989), a concept comparing brain aging...

The microtubule-associated protein Tau plays a crucial role in regulating the dynamic stability of microtubules during neuronal development and synaptic transmission. In a group of neurodegenerative diseases, such as Alzheimer disease and other tauopathies, conformational changes in Tau are associated with the initial stages of disease pathology. F...

Imbalanced protein load within cells is a critical aspect for most diseases of aging. In particular, the accumulation of proteins into neurotoxic aggregates is a common thread for a host of neurodegenerative diseases. Our previous work demonstrated that age-related changes to the cellular chaperone repertoire contributes to abnormal buildup of the...

Neurodegenerative diseases caused by abnormal accumulation of the microtubule associated protein tau (MAPT, tau) are collectively called tauopathies. The most devastating tau related disorder is Alzheimer's disease (AD). Molecular chaperones such as heat shock proteins (Hsp) have emerged as critical regulators of tau stability. Several studies from...

Members of the 70-kDa heat shock family can control and manipulate a host of oncogenic client proteins. This role of Hsp70 in both the folding and degradation of these client proteins makes it a potential drug target for certain forms of cancer. The phenothiazine family of compounds, as well as the flavonoid myricetin, was recently shown to inhibit...

Alzheimer's disease and other tauopathies have recently been clustered with a group of nervous system disorders termed protein misfolding diseases. The common element established between these disorders is their requirement for processing by the chaperone complex. It is now clear that the individual components of the chaperone system, such as Hsp70...

https://deepblue.lib.umich.edu/bitstream/2027.42/152817/1/alzjjalz200904510.pdf

Introduction Chaperone regulation in Alzheimer's disease Conclusions Abstract Molecular chaperones and heat shock proteins (Hsp) have emerged as critical regulators of proteins associated with neurodegenerative disease pathologies. The very nature of the chaperone system, which is to maintain protein quality control, means that most nascent protei...

We have extensively analyzed the biochemical and histochemical profiles of the tau protein from the rTg4510 transgenic mouse model in which the animals uniquely develop forebrain tau pathologies similar to those found in human tauopathies. Levels of several soluble phosphorylated tau species were highest at 1 month relative to later time points, su...

A hallmark of the pathology of Alzheimer's disease is the accumulation of the microtubule-associated protein tau into fibrillar aggregates. Recent studies suggest that they accumulate because cytosolic chaperones fail to clear abnormally phosphorylated tau, preserving a pool of toxic tau intermediates within the neuron. We describe a mechanism for...

The Hsp70 family of molecular chaperones is essential for protein folding, re-folding misfolded client proteins, clearance of aberrant client proteins, and can also inhibit programmed cell death. There are two major cytosolic members of this family: the constitutive Hsc70, and the inducible Hsp72. Under stress conditions the Hsp70 family protects t...