Decrease of neuronal FKBP4/FKBP52 modulates perinuclear lysosomal positioning and MAPT/Tau behavior during MAPT/Tau-induced proteotoxic stress

FKBP4 promotes glycolysis and hepatocellular carcinoma progression via p53/HK2 axis

FKBP4, a member of the FK506-binding protein (FKBP) family, is a promising target for a variety of disorders, including cancer. However, its underlying molecular mechanism and potential function in hepatocellular carcinoma (HCC) are largely elusive. Therefore, we aimed to investigate the expression status, functional implications and underlying mechanisms of FKBP4 in HCC. Our bioinformatics analysis of TCGA LIHC datasets, ICGC LIRI-JP datasets and GEO datasets results showed FKBP4 was upregulated in HCC tissues. We also confirmed the elevated FKBP4 in clinical HCC samples. Additionally, quantitative RT-PCR results revealed FKBP4 was highly expressed in all five tested HCC cell lines. We also observed a correlation between elevated FKBP4 expression and poor prognosis in HCC patients. Loss of FKBP4 can inhibit the proliferation and migration in HCC cells. Furthermore, we found that silencing FKBP4 suppressed glucose uptake, lactic acid production and 18F-FDG uptake compared with the control group. Mechanistically, our funding indicated that FKBP4 participates in glycolysis through p53 mediated HK2 signaling pathway, specially, FKBP4 knockdown promotes the expression and stability of p53 protein rather than affecting the transcription level. Finally, rescue experiments revealed that simultaneous knockdown of both FKBP4 and p53 partially reversed the inhibitory effects on HK2 protein levels and 18F-FDG uptake. Our study elucidates a novel role of FKBP4 in promoting HCC development and glycolysis by modulating the p53/HK2 signaling pathway. Given the critical role of aerobic glycolysis in the progression of HCC, targeting FKBP4 may offer a new therapeutic strategy for treating this malignancy.

A Map of Transcriptomic Signatures of Different Brain Areas in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder that progressively involves brain regions with an often-predictable pattern. Damage to the brain appears to spread and worsen with time, but the molecular mechanisms underlying the region-specific distribution of AD pathology at different stages of the disease are still under-investigated. In this study, a whole-transcriptome analysis was carried out on brain samples from the hippocampus (HI), temporal and parietal cortices (TC and PC, respectively), cingulate cortex (CG), and substantia nigra (SN) of six subjects with a definite AD diagnosis and three healthy age-matched controls in duplicate. The transcriptomic results showed a greater number of differentially expressed genes (DEGs) in the TC (1571) and CG (1210) and a smaller number of DEGs in the HI (206), PC (109), and SN (60). Furthermore, the GSEA showed a difference between the group of brain areas affected early (HI and TC) and the group of areas that were subsequently involved (PC, CG, and SN). Notably, in the HI and TC, there was a significant downregulation of shared DEGs primarily involved in synaptic transmission, while in the PC, CG, and SN, there was a significant downregulation of genes primarily involved in protein folding and trafficking. The course of AD could follow a definite time- and severity-related pattern that arises from protein misfolding, as observed in the PC, CG, and SN, and leads to synaptic impairment, as observed in the HI and TC. Therefore, a map of the molecular and biological processes involved in AD pathogenesis may be traced. This could aid in the discovery of novel biological targets in order to develop effective and well-timed therapeutic approaches.

Targeting PNPO to suppress tumor growth via inhibiting autophagic flux and to reverse paclitaxel resistance in ovarian cancer

Our previous study showed that pyridoxine 5'-phosphate oxidase (PNPO) is a tissue biomarker of ovarian cancer (OC) and has a prognostic implication but detailed mechanisms remain unclear. The current study focused on PNPO-regulated lysosome/autophagy-mediated cellular processes and the potential role of PNPO in chemoresistance. We found that PNPO was overexpressed in OC cells and was a prognostic factor in OC patients. PNPO significantly promoted cell proliferation via the regulation of cyclin B1 and phosphorylated CDK1 and shortened the G2M phase in a cell cycle. Overexpressed PNPO enhanced the biogenesis and perinuclear distribution of lysosomes, promoting the degradation of autophagosomes and boosting the autophagic flux. Further, an autolysosome marker LAMP2 was upregulated in OC cells. Silencing LAMP2 suppressed cell growth and induced cell apoptosis. LAMP2-siRNA blocked PNPO action in OC cells, indicating that the function of PNPO on cellular processes was mediated by LAMP2. These data suggest the existence of the PNPO-LAMP2 axis. Moreover, silencing PNPO suppressed xenographic tumor formation. Chloroquine counteracted the promotion effect of PNPO on autophagic flux and inhibited OC cell survival, facilitating the inhibitory effect of PNPO-shRNA on tumor growth in vivo. Finally, PNPO was overexpressed in paclitaxel-resistant OC cells. PNPO-siRNA enhanced paclitaxel sensitivity in vitro and in vivo. In conclusion, PNPO has a regulatory effect on lysosomal biogenesis that in turn promotes autophagic flux, leading to OC cell proliferation, and tumor formation, and is a paclitaxel-resistant factor. These data imply a potential application by targeting PNPO to suppress tumor growth and reverse PTX resistance in OC.

The potential role of gut microbiota-derived metabolites as regulators of metabolic syndrome-associated mitochondrial and endolysosomal dysfunction in Alzheimer's disease

Although the role of gut microbiota (GMB)-derived metabolites in mitochondrial and endolysosomal dysfunction in Alzheimer's disease (AD) under metabolic syndrome remains unclear, deciphering these host-metabolite interactions represents a major public health challenge. Dysfunction of mitochondria and endolysosomal networks (ELNs) plays a crucial role in metabolic syndrome and can exacerbate AD progression, highlighting the need to study their reciprocal regulation for a better understanding of how AD is linked to metabolic syndrome. Concurrently, metabolic disorders are associated with alterations in the composition of the GMB. Recent evidence suggests that changes in the composition of the GMB and its metabolites may be involved in AD pathology. This review highlights the mechanisms of metabolic syndrome-mediated AD development, focusing on the interconnected roles of mitochondrial dysfunction, ELN abnormalities, and changes in the GMB and its metabolites. We also discuss the pathophysiological role of GMB-derived metabolites, including amino acids, fatty acids, other metabolites, and extracellular vesicles, in mediating their effects on mitochondrial and ELN dysfunction. Finally, this review proposes therapeutic strategies for AD by directly modulating mitochondrial and ELN functions through targeting GMB metabolites under metabolic syndrome.

A decrease in Fkbp52 alters autophagosome maturation and A152T-tau clearance in vivo

The failure of the autophagy-lysosomal pathway to clear the pathogenic forms of Tau exacerbates the pathogenesis of tauopathies. We have previously shown that the immunophilin FKBP52 interacts both physically and functionally with Tau, and that a decrease in FKBP52 protein levels is associated with Tau deposition in affected human brains. We have also shown that FKBP52 is physiologically present within the lysosomal system in healthy human neurons and that a decrease in FKBP52 expression alters perinuclear lysosomal positioning and Tau clearance during Tau-induced proteotoxic stress in vitro. In this study, we generate a zebrafish fkbp4 loss of function mutant and show that axonal retrograde trafficking of Lamp1 vesicles is altered in this mutant. Moreover, using our transgenic HuC::mCherry-EGFP-LC3 line, we demonstrate that the autophagic flux is impaired in fkbp4 mutant embryos, suggesting a role for Fkbp52 in the maturation of autophagic vesicles. Alterations in both axonal transport and autophagic flux are more evident in heterozygous rather than homozygous fkbp4 mutants. Finally, taking advantage of the previously described A152T-Tau transgenic fish, we show that the clearance of pathogenic A152T-Tau mutant proteins is slower in fkbp4 +/- mutants in comparison to fkbp4 +/+ larvae. Altogether, these results indicate that Fkbp52 is required for the normal trafficking and maturation of lysosomes and autophagic vacuoles along axons, and that its decrease is sufficient to hinder the clearance of pathogenic Tau in vivo.

Reduced lysosomal density in neuronal dendrites mediates deficits in synaptic plasticity in Huntington's disease

Huntington's disease (HD) usually causes cognitive disorders, including learning difficulties, that emerge before motor symptoms. Mutations related to lysosomal trafficking are linked to the pathogenesis of neurological diseases, whereas the cellular mechanisms remain elusive. Here, we discover a reduction in the dendritic density of lysosomes in the hippocampus that correlates with deficits in synaptic plasticity and spatial learning in early CAG-140 HD model mice. We directly manipulate intraneuronal lysosomal positioning with light-induced CRY2:CIB1 dimerization and demonstrate that lysosomal abundance in dendrites positively modulates long-term potentiation of glutamatergic synapses onto the neuron. This modulation depends on lysosomal Ca2+ release, which further promotes endoplasmic reticulum (ER) entry into spines. Importantly, optogenetically restoring lysosomal density in dendrites rescues the synaptic plasticity deficit in hippocampal slices of CAG-140 mice. Our data reveal dendritic lysosomal density as a modulator of synaptic plasticity and suggest a role of lysosomal mispositioning in cognitive decline in HD.

Aggregation, Transmission, and Toxicity of the Microtubule-Associated Protein Tau: A Complex Comprehension

The microtubule-associated protein tau is an intrinsically disordered protein containing a few short and transient secondary structures. Tau physiologically associates with microtubules (MTs) for its stabilization and detaches from MTs to regulate its dynamics. Under pathological conditions, tau is abnormally modified, detaches from MTs, and forms protein aggregates in neuronal and glial cells. Tau protein aggregates can be found in a number of devastating neurodegenerative diseases known as "tauopathies", such as Alzheimer's disease (AD), frontotemporal dementia (FTD), corticobasal degeneration (CBD), etc. However, it is still unclear how the tau protein is compacted into ordered protein aggregates, and the toxicity of the aggregates is still debated. Fortunately, there has been considerable progress in the study of tau in recent years, particularly in the understanding of the intercellular transmission of pathological tau species, the structure of tau aggregates, and the conformational change events in the tau polymerization process. In this review, we summarize the concepts of tau protein aggregation and discuss the views on tau protein transmission and toxicity.

The accelerated organ senescence and proteotoxicity in thyrotoxicosis mice

The mechanism of aging has always been the focus of research, because aging is related to disease susceptibility and seriously affects people's quality of life. The diseases also accelerate the aging process, especially the pathological changes of substantive organs, such as cardiac hypertrophy, severely shortened lifespan. So, lesions in organs are both a consequence and a cause of aging. However, the disease in a given organ is not in isolation but is a systemic problem. Our previous study found that thyrotoxicosis mice model has aging characteristics including immunosenescence, lipotoxicity, malnutrition. But all these characteristics will lead to organ senescence, therefore, this study continued to study the aging changes of important organs such as heart, liver, and kidney in thyrotoxicosis mice using tandem mass tags (TMT) proteomics method. The results showed that the excess thyroxine led to cardiac hypertrophy. In the liver, the ability to synthesize functional proteins, detoxify, and metabolism were declined. The effect on the kidney was the decreased ability of detoxify and metabolism. The main finding of the present study was that the acceleration of organ senescence by excess thyroxine was due to proteotoxicity. The shared cause of proteotoxicity in the three organs included the intensify of oxidative phosphorylation, the redundancy production of ribosomes, and the lack of splicing and ubiquitin proteasome system function. Totally, proteotoxicity was another parallel between thyrotoxicosis and aging in addition to lipotoxicity. Our research provided a convenient and appropriate animal model for exploring aging mechanism and antiaging drugs.

Friend or foe: role of pathological tau in neuronal death

Neuronal death is one of the most common pathological hallmarks of diverse neurological diseases, which manifest varying degrees of cognitive or motor dysfunction. Neuronal death can be classified into multiple forms with complicated and unique regulatory signaling pathways. Tau is a key microtubule-associated protein that is predominantly expressed in neurons to stabilize microtubules under physiological conditions. In contrast, pathological tau always detaches from microtubules and is implicated in a series of neurological disorders that are characterized by irreversible neuronal death, such as necrosis, apoptosis, necroptosis, pyroptosis, ferroptosis, autophagy-dependent neuronal death and phagocytosis by microglia. However, recent studies have also revealed that pathological tau can facilitate neuron escape from acute apoptosis, delay necroptosis through its action on granulovacuolar degeneration bodies (GVBs), and facilitate iron export from neurons to block ferroptosis. In this review, we briefly describe the current understanding of how pathological tau exerts dual effects on neuronal death by acting as a double-edged sword in different neurological diseases. We propose that elucidating the mechanism by which pathological tau affects neuronal death is critical for exploring novel and precise therapeutic strategies for neurological disorders.

Concomitant Neuronal Tau Deposition and FKBP52 Decrease Is an Early Feature of Different Human and Experimental Tauopathies

BACKGROUND

Pathological tau proteins constitute neurofibrillary tangles that accumulate in tauopathies including Alzheimer's disease (AD), progressive supranuclear palsy (PSP), and familial frontotemporal lobar degeneration (FTLD-Tau). We previously showed that the FKBP52 immunophilin interacts functionally with tau and strongly decreases in AD brain neurons in correlation with tau deposition. We also reported that FKBP52 co-localizes with autophagy-lysosomal markers and an early pathological tau isoform in AD neurons, suggesting its involvement in autophagic tau clearance.

OBJECTIVE

Our objective was to evaluate if differences in neuronal FKBP52 expression levels and subcellular localization might be detected in AD, PSP, familial FTLD-Tau, and in the hTau-P301 S mouse model compared to controls.

METHODS

Cell by cell immunohistofluorescence analyses and quantification of FKBP52 were performed on postmortem brain samples of some human tauopathies and on hTau-P301 S mice spinal cords.

RESULTS

We describe a similar FKBP52 decrease and its localization with early pathological tau forms in the neuronal autophagy-lysosomal pathway in various tauopathies and hTau-P301 S mice. We find that FKBP52 decreases early during the pathologic process as it occurs in rare neurons with tau deposits in the marginally affected frontal cortex region of AD Braak IV brains and in the spinal cord of symptomless 1-month-old hTau-P301 S mice.

CONCLUSION

As FKBP52 plays a significant role in cellular signaling and conceivably in tau clearance, our data support the idea that the prevention of FKBP52 decrease or the restoration of its normal expression at early pathologic stages might represent a new potential therapeutic approach in tauopathies including AD, familial FTLD-Tau, and PSP.

FKBP52 in Neuronal Signaling and Neurodegenerative Diseases: A Microtubule Story

The FK506-binding protein 52 (FKBP52) belongs to a large family of ubiquitously expressed and highly conserved proteins (FKBPs) that share an FKBP domain and possess Peptidyl-Prolyl Isomerase (PPIase) activity. PPIase activity catalyzes the isomerization of Peptidyl-Prolyl bonds and therefore influences target protein folding and function. FKBP52 is particularly abundant in the nervous system and is partially associated with the microtubule network in different cell types suggesting its implication in microtubule function. Various studies have focused on FKBP52, highlighting its importance in several neuronal microtubule-dependent signaling pathways and its possible implication in neurodegenerative diseases such as tauopathies (i.e., Alzheimer disease) and alpha-synucleinopathies (i.e., Parkinson disease). This review summarizes our current understanding of FKBP52 actions in the microtubule environment, its implication in neuronal signaling and function, its interactions with other members of the FKBPs family and its involvement in neurodegenerative disease.

Targeting Chaperone/Co-Chaperone Interactions with Small Molecules: A Novel Approach to Tackle Neurodegenerative Diseases

The dysfunction of the proteostasis network is a molecular hallmark of neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis. Molecular chaperones are a major component of the proteostasis network and maintain cellular homeostasis by folding client proteins, assisting with intracellular transport, and interfering with protein aggregation or degradation. Heat shock protein 70 kDa (Hsp70) and 90 kDa (Hsp90) are two of the most important chaperones whose functions are dependent on ATP hydrolysis and collaboration with their co-chaperones. Numerous studies implicate Hsp70, Hsp90, and their co-chaperones in neurodegenerative diseases. Targeting the specific protein–protein interactions between chaperones and their particular partner co-chaperones with small molecules provides an opportunity to specifically modulate Hsp70 or Hsp90 function for neurodegenerative diseases. Here, we review the roles of co-chaperones in Hsp70 or Hsp90 chaperone cycles, the impacts of co-chaperones in neurodegenerative diseases, and the development of small molecules modulating chaperone/co-chaperone interactions. We also provide a future perspective of drug development targeting chaperone/co-chaperone interactions for neurodegenerative diseases.

Autophagy and Tau Protein

Neurofibrillary tangles, which consist of highly phosphorylated tau protein, and senile plaques (SPs) are pathological hallmarks of Alzheimer's disease (AD). In swollen axons, many autophagic vacuoles are observed around SP in the AD brain. This suggests that autophagy function is disturbed in AD. We used a neuronal cellular model of tauopathy (M1C cells), which harbors wild type tau (4R0N), to assess the effects of the lysosomotrophic agent NH4Cl, and autophagy inhibitors chloroquine and 3 methyladenine (3MA). It was found that chloroquine, NH4Cl and 3MA markedly increased tau accumulation. Thus, autophagy lysosomal system disturbances disturbed the degradation mechanisms of tau protein. Other studies also revealed that tau protein, including aggregated tau, is degraded via the autophagy lysosome system. Phosphorylated and C terminal truncated tau were also reported to disturb autophagy function. As a therapeutic strategy, autophagy upregulation was suggested. Thus far, as autophagy modulators, rapamycin, mTOCR1 inhibitor and its analogues, lithium, metformin, clonidine, curcumin, nicotinamide, bexaroten, and torehalose have been proposed. As a therapeutic strategy, autophagic modulation may be the next target of AD therapeutics.

Inhibition of heat shock proteins increases autophagosome formation, and reduces the expression of APP, Tau, SOD1 G93A and TDP-43

Aberrant expression and denaturation of Tau, amyloid-beta and TDP-43 can lead to cell death and is a major component of pathologies such as Alzheimer’s Disease (AD). AD neurons exhibit a reduced ability to form autophagosomes and degrade proteins via autophagy. Using genetically manipulated colon cancer cells we determined whether drugs that directly inhibit the chaperone ATPase activity or cause chaperone degradation and endoplasmic reticulum stress signaling leading to macroautophagy could reduce the levels of these proteins. The antiviral chaperone ATPase inhibitor AR12 reduced the ATPase activities and total expression of GRP78, HSP90, and HSP70, and of Tau, Tau 301L, APP, APP692, APP715, SOD1 G93A and TDP-43. In parallel, it increased the phosphorylation of ATG13 S318 and eIF2A S51 and caused eIF2A-dependent autophagosome formation and autophagic flux. Knock down of Beclin1 or ATG5 prevented chaperone, APP and Tau degradation. Neratinib, used to treat HER2+ breast cancer, reduced chaperone levels and expression of Tau and APP via macroautophagy, and neratinib interacted with AR12 to cause further reductions in protein levels. The autophagy-regulatory protein ATG16L1 is expressed as two isoforms, T300 or A300: Africans trend to express T300 and Europeans A300. We observed higher basal expression of Tau in T300 cells when compared to isogenic A300 cells. ATG16L1 isoform expression did not alter basal levels of HSP90, HSP70 or HSP27, however, basal levels of GRP78 were reduced in A300 cells. The abilities of both AR12 and neratinib to stimulate ATG13 S318 and eIF2A S51 phosphorylation and autophagic flux was also reduced in A300 cells. Our data support further evaluation of AR12 and neratinib in neuronal cells as repurposed treatments for AD.

FKBP4 integrates FKBP4/Hsp90/IKK with FKBP4/Hsp70/RelA complex to promote lung adenocarcinoma progression via IKK/NF-κB signaling

FKBP4 belongs to the family of immunophilins, which serve as a regulator for steroid receptor activity. Thus, FKBP4 has been recognized to play a critical role in several hormone-dependent cancers, including breast and prostate cancer. However, there is still no research to address the role of FKBP4 on lung adenocarcinoma (LUAD) progression. We found that FKBP4 expression was elevated in LUAD samples and predicted significantly shorter overall survival based on TCGA and our cohort of LUAD patients. Furthermore, FKBP4 robustly increased the proliferation, metastasis, and invasion of LUAD in vitro and vivo. Mechanistic studies revealed the interaction between FKBP4 and IKK kinase complex. We found that FKBP4 potentiated IKK kinase activity by interacting with Hsp90 and IKK subunits and promoting Hsp90/IKK association. Also, FKBP4 promotes the binding of IKKγ to IKKβ, which supported the facilitation role in IKK complex assembly. We further identified that FKBP4 TPR domains are essential for FKBP4/IKK interaction since its association with Hsp90 is required. In addition, FKBP4 PPIase domains are involved in FKBP4/IKKγ interaction. Interestingly, the association between FKBP4 and Hsp70/RelA favors the transport of RelA toward the nucleus. Collectively, FKBP4 integrates FKBP4/Hsp90/IKK with FKBP4/Hsp70/RelA complex to potentiate the transcriptional activity and nuclear translocation of NF-κB, thereby promoting LUAD progression. Our findings suggest that FKBP4 may function as a prognostic biomarker of LUAD and provide a newly mechanistic insight into modulating IKK/NF-κB signaling.