Publications

The 13th International Symposium on Heat Shock Proteins in Biology, Medicine and the Environment, organized by the Cell Stress Society International (CSSI), was held in October 2025 in Syracuse, NY, and brought together investigators spanning basic, translational, and clinical stress biology. The meeting highlighted the continued evolution of the heat shock response from a canonical transcriptional program to a complex, multi-layered network integrating transcriptional condensates, posttranslational regulation of chaperones, spatial organization, and system-level stress adaptation. Scientific sessions showcased advances in stress-induced transcription and genome control, the expanding Hsp90/Hsp70 "chaperone code," proteostasis and protein quality control, mitochondrial chaperones and metabolic regulation, cancer-immune interfaces, host-pathogen interactions, and the roles of chaperones in aging and neurodegenerative disease. Particular emphasis was placed on emerging therapeutic and diagnostic strategies, including isoform-specific chaperone inhibitors, co-chaperone targeting, theranostic approaches, and clinical-stage candidates. Systems-level analyses of stress resilience, extracellular chaperone signaling, and organismal adaptation further underscored the breadth of stress biology across scales. The symposium also honored the legacy of Dr Len Neckers, whose pioneering contributions to Hsp90 biology shaped the field, and recognized outstanding scientific achievements through CSSI awards and fellowships. Collectively, the work presented reflects a field that continues to deepen mechanistic understanding while advancing toward precision-based therapeutic and diagnostic applications. This meeting report summarizes these developments and highlights future directions for stress biology research.

The 51 kDa FK506-binding protein (FKBP51) has been studied for its involvement in regulating multiple biological systems, particularly as a regulator of steroid hormone receptors, but roles in metabolism, pain response, cell survival, protein turnover, autophagy, immune response, and insulin signaling have also been described. Genetic variants of FKBP51 are associated with various stress-related mental disorders. While recent research has clarified aspects of these processes, the complete range of FKBP51 interactions remains undetermined. FKBP52, a closely related homolog, also affects similar pathways. Recent studies have identified new protein partners for FKBP51 and FKBP52, suggesting an even broader interactome with transient associations. To further characterize interactions, TurboID-based proximity labeling was performed in HeLa cells. Proteomic analysis confirmed known FKBP51 and FKBP52 interactions, while also identifying additional shared and unique binding partners with strong enrichment in metabolic pathways, amino acid biosynthesis, and carbon metabolism. Although FKBP51 and FKBP52 proximal proteins were primarily cytosolic, FKBP51 showed additional associations with exosomal proteins while FKBP52 engaged with additional nuclear proteins. These findings highlight the overlapping roles in metabolic signaling and differentiate pathway-specific partners.

Alzheimer's disease (AD) includes a defining hallmark that correlates most closely to cognitive decline, namely misfolded tau protein. However, the "upstream" etiology and downstream clinical manifestations of tauopathies are quite diverse. Tau deposition elicits different pathological phenotypes and outcomes depending on the tau strain, proteoforms, and regional susceptibility. Posttranslational modifications (PTM) can alter tau structure, function, networks, and its pathological sequelae. We uncovered tau citrullination on multiple epitopes caused by peptidyl arginine deiminase (PAD) enzymes. PAD-induced citrullination irreversibly converts arginine residues to citrulline, producing a net loss of positive charge, elimination of pi-pi interactions, and increased hydrophobicity. We observed increased PAD2 and PAD4 in Alzheimer's disease (AD) brain and that they both can citrullinate tau. Tau can become citrullinated by PADs at all 14 arginine residues throughout the N-terminal domain (N-term), proline-rich domain (PR), microtubule-binding repeats domain (MBR), and C-terminal domain (C-term) on full-length tau (2N4R). Citrullination of tau impacts fibrillization and oligomerization rates in aggregation assays. Utilizing a panel of novel citrullinated tau (citR tau) antibodies, we identified citrullination of tau in vitro, several animal models of tauopathies, and Alzheimer's disease (AD). CitR tau increased with Braak stage and was enriched in AD brains with higher pathological tau burden. This work provides a new area of tau biology that signifies further consideration in the emerging spectrum of tauopathies and its clinical understanding.

Circadian rhythm disruptions have been associated with a wide range of health issues and complications, including an increased risk of circadian rhythm sleep disorders (CRSDs). CRSDs are common among individuals who have been through a traumatic event, particularly in those who have post-traumatic stress disorder (PTSD). Allelic variations in the gene encoding for FK506-binding protein 51 (FKBP51) can increase the susceptibility for PTSD and other stress-related disorders following trauma. At least one of these variants increases the levels of FKBP51 following stress through a glucocorticoid receptor-mediated process. Here, we used a mouse model that overexpresses human FKBP51 throughout the forebrain, rTgFKBP5, to investigate if elevated FKBP51 contributes to circadian rhythm disruption. Surprisingly, our findings indicate a greater rhythm amplitude and decreased rhythm fragmentation in rTgFKBP5 mice, particularly females, compared to controls. Female rTgFKBP5 mice also showed higher corticosterone levels basally and following stress exposure. Overall, this study associates FKBP51 overexpression with beneficial circadian rhythm outcomes.

FKBP51, also known as FK506-binding protein 51, is a molecular chaperone and scaffolding protein with significant roles in regulating hormone signaling and responding to stress. Genetic variants in FKBP5, which encodes FKBP51, have been implicated in a growing number of neuropsychiatric disorders, which has spurred efforts to target FKBP51 therapeutically. However, the molecular mechanisms and sub-anatomical regions influenced by FKBP51 in these disorders are not fully understood. In this study, we aimed to examine the impact of Fkbp5 ablation using circadian phenotyping and molecular analyses. Our findings revealed that the lack of FKBP51 did not significantly alter circadian rhythms, as detected by wheel-running activity, but did offer protection against stress-mediated disruptions in rhythmicity in a sex-dependent manner. Protein changes in Fkbp5 KO mice, as measured by histology and proteomics, revealed alterations in a brain region- and sex-dependent manner. Notably, regardless of sex, aged Fkbp5 KOs showed elevated MYCBP2, FBXO45, and SPRYD3 levels, which are associated with neuronal-cell adhesion and synaptic integrity. Additionally, pathways such as serotonin receptor signaling and S100 family signaling were differentially regulated in Fkbp5 KO mice. Weighted protein correlation network analysis identified protein networks linked with synaptic transmission and neuroinflammation. The information generated by this work can be used to better understand the molecular changes in the brain during aging and in the absence of Fkbp5, which has implications for the continued development of FKBP51-focused therapeutics for stress-related disorders.

FK506 binding protein 51 (FKBP51) is a molecular chaperone that influences stress response. In addition to having an integral role in the regulation of steroid hormone receptors, including glucocorticoid receptor, FKBP51 has been linked with several biological processes including metabolism and neuronal health. Genetic and epigenetic alterations in the gene that encodes FKBP51, FKBP5, are associated with increased susceptibility to multiple neuropsychiatric disorders, which has fueled much of the research on this protein. Because of the complexity of these processes, animal models have been important in understanding the role of FKBP51. This review examines each of the current mouse models of FKBP5, which include whole animal knockout, conditional knockout, overexpression, and humanized mouse models. The generation of each model and observational details are discussed, including behavioral phenotypes, molecular changes, and electrophysiological alterations basally and following various challenges. While much has been learned through these models, there are still many aspects of FKBP51 biology that remain opaque and future studies are needed to help illuminate these current gaps in knowledge. Overall, FKBP5 continues to be an exciting potential target for stress-related disorders.

Alzheimer's disease and related tauopathies are characterized by the pathogenic misfolding and aggregation of the microtubule-associated protein tau. Understanding how endogenous chaperones modulate tau misfolding could guide future therapies. Here, we show that the immunophilin FKBP12, the 12-kDa FK506-binding protein (also known as FKBP prolyl isomerase 1A), regulates the neuronal resilience by chaperoning a specific structure in monomeric tau. Using a combination of mouse and cell experiments, in vitro aggregation experiments, nuclear magnetic resonance-based structural analysis of monomeric tau, site-specific phosphorylation and mutation, as well as structure-based analysis using the neural network-based structure prediction program AlphaFold, we define the molecular factors that govern the binding of FKBP12 to tau and its influence on tau-induced neurotoxicity. We further demonstrate that tyrosine phosphorylation of tau blocks the binding of FKBP12 to two highly specific structural motifs in tau. Our data together with previous results demonstrating FKBP12/tau colocalization in neurons and neurofibrillary tangles support a critical role of FKBP12 in regulating tau pathology.

Shifts in normal aging set stage for neurodegeneration and dementia affecting 1 in 10 adults. The study demonstrates that lncRNA GAS5 is decreased in aged and Alzheimer's disease brain. The role and targets of lncRNA GAS5 in the aging brain were elucidated using a GAS5-targeting small molecule NPC86, a frontier in lncRNA-targeting therapeutic. Robust techniques such as molecular dynamics simulation of NPC86 binding to GAS5, in vitro functional assays demonstrating that GAS5 regulates insulin signaling, neuronal survival, phosphorylation of tau, and neuroinflammation via toll-like receptors support the role of GAS5 in maintaining healthy neurons. The study demonstrates the safety and efficacy of intranasal NPC86 treatment in aged mice to improve cellular functions with transcriptomic analysis in response to NPC86. In summary, the study demonstrates that GAS5 contributes to pathways associated with neurodegeneration and NPC86 has tremendous therapeutic potential to prevent the advent of neurodegenerative diseases and dementias.

The aberrant accumulation of tau protein is implicated as a pathogenic factor in many neurodegenerative diseases. Tau seeding may underlie its predictable spread in these diseases. Molecular chaperones can modulate tau pathology, but their effects have mainly been studied in isolation. This study employed a semi-high throughput assay to identify molecular chaperones influencing tau seeding using Tau RD P301S FRET Biosensor cells, which express a portion of tau containing the frontotemporal dementia-related P301S tau mutation fused to a FRET biosensor. Approximately fifty chaperones from five major families were screened using live cell imaging to monitor FRET-positive tau seeding. Among the tested chaperones, five exhibited significant effects on tau in the primary screen. Notably, three of these were from the DnaJ family. In subsequent studies, overexpression of DnaJA2, DnaJB1, and DnaJB6b resulted in significant reductions in tau levels. Knockdown experiments by shRNA revealed an inverse correlation between DnaJB1 and DnaJB6b with tau levels. DnaJB6b overexpression, specifically, reduced total tau levels in a cellular model with a pre-existing pool of tau, partially through enhanced proteasomal degradation. Further, DnaJB6b interacted with tau complexes. These findings highlight the potent chaperone activity within the DnaJ family, particularly DnaJB6b, towards tau.

The accumulation and aggregation of the microtubule-associated protein tau (tau) into intracellular neuronal tangles are a hallmark of a range of progressive neurodegenerative tauopathies, including Alzheimer's disease (AD), frontotemporal dementia, Pick's disease, and progressive supranuclear palsy. The aberrant phosphorylation of tau is associated with tau aggregates in AD. Members of the heat shock protein 70 kDa (Hsp70) family of chaperones bind directly to tau and modulate tau clearance and aggregation. Small molecules that inhibit the Hsp70 family of chaperones have been shown to reduce the accumulation of tau, including phosphorylated tau. Here, eight analogs of the rhodacyanine inhibitor, JG-98, were synthesized and evaluated. Like JG-98, many of the compounds inhibited ATPase activity of the cytosolic heat shock cognate 70 protein (Hsc70) and reduced total, aggregated, and phosphorylated tau accumulation in cultured cells. Three compounds, representing divergent clogP values, were evaluated for in vivo blood-brain barrier penetration and tau reduction in an ex vivo brain slice model. AL69, the compound with the lowest clogP and the lowest membrane retention in a parallel artificial membrane permeability assay (PAMPA), reduced phosphorylated tau accumulation. Our results suggest that benzothiazole substitutions of JG-98 that increase hydrophilicity may increase the efficacy of these Hsp70 inhibitors to reduce phosphorylated tau.