FK506 binding protein 5 (FKBP5) is a peptidyl propyl cis-trans isomerase that has been shown to interact with cellular immune pathways such as calcineurin and NF-κB. During an influenza infection, FKBP5 is up-regulated at the lung in an in vivo ferret infection model, yet the effect of FKBP5 on influenza replication and immune response is not understood. An in vitro model of human alveolar epithelial cell line A549 was established to study the cause and the function of FKBP5 up-regulation during an influenza infection. In this in vitro model, FKBP5 was not up-regulated by influenza replication, but instead it was up-regulated when A549 cells were treated with glucocorticoid. FKBP5 up-regulation did not have any effect on rate of influenza replication. However, FKBP5 up-regulation mediated the suppressive effect of glucocorticoid on pro-inflammatory cytokine production, since FKBP5 knock-down by siRNA increased cytokine production in the presence of glucocorticoid. Overall, the results suggested that the up-regulation of FKBP5 is a physiological response of lung cells to the increase of glucocorticoid during influenza infections, which facilitates the suppressive effect of glucocorticoid on pro-inflammatory cytokine production.

FK506 binding protein 5 (FKBP5) is a peptidyl propyl cis-trans isomerase that has been shown to interact with cellular immune pathways such as calcineurin and NF-κB. During an influenza infection, FKBP5 is up-regulated at the lung in an in vivo ferret infection model, yet the effect of FKBP5 on influenza replication and immune response is not understood. An in vitro model of human alveolar epithelial cell line A549 was established to study the cause and the function of FKBP5 up-regulation during an influenza infection. In this in vitro model, FKBP5 was not up-regulated by influenza replication, but instead it was up-regulated when A549 cells were treated with glucocorticoid. FKBP5 up-regulation did not have any effect on rate of influenza replication. However, FKBP5 up-regulation mediated the suppressive effect of glucocorticoid on pro-inflammatory cytokine production, since FKBP5 knock-down by siRNA increased cytokine production in the presence of glucocorticoid. Overall, the results suggested that the up-regulation of FKBP5 is a physiological response of lung cells to the increase of glucocorticoid during influenza infections, which facilitates the suppressive effect of glucocorticoid on pro-inflammatory cytokine production.

Tau is a protein which regulates microtubule stability and is heavily involved in axonal transport. This stability is dynamically controlled in part by over 40 phosphorylation sites across the tau protein which allows for binding and release from the microtubules. However, if abnormal hyperphosphorylation occurs, tau dissociates from the microtubules. Once released, the microtubules become unstable and the aberrant tau mislocalizes from the axon to the somatodendric compartment, where it aggregates. These aggregates are made of many pathological forms of tau including oligomeric species, paired helical filaments, and neurofibrillary tangles, all of which have associated toxicities. Tau pathology is a hallmark of Alzheimer's disease, one of over 15 diseases known as tauopathies which present with tau pathology, all of which lack effective treatments. Heat shock protein 90 kDa (Hsp90) is a major adenosine triphosphate (ATP)-dependent regulator of non-native proteins, like misfolded tau. Although Hsp90 is able to effectively refold and degrade many aberrant proteins, it has been associated with preserving aberrant tau. In fact, inhibiting the Hsp90 ATPase activity leads to the degradation of tau, which has been demonstrated in a number of models with the use of various Hsp90 inhibitors. However, there are many side-effects associated with the use of these inhibitors including toxicity and heat shock factor 1 (HSF1) activation. Although improvements on Hsp90 inhibitors are still in progress, this study explores targeting Hsp90 through a slightly different mechanism, by targeting Hsp90 co-chaperones. Hsp90 is involved in almost every pathway in each cell throughout the body. Co-chaperone proteins assist Hsp90 in these various processes, but are each only involved in a subset of the total Hsp90 interactome. Therefore, targeting Hsp90 co-chaperones could lead to improved efficacy, potency, and safety of drugs designed toward Hsp90 for the treatment of tauopathies. We previously showed one of these co-chaperones, FK506 binding protein 51 kDa (FKBP51), a tetratricopeptide repeat (TPR) domain containing immunophilin, coordinates with Hsp90 to regulate tau metabolism. More specifically, we found that increases and decreases in FKBP51 levels correlated with increases and decreases in tau levels, respectively. FKBP51 knockout mice have been extensively studied and have shown no negative phenotypes in these characterizations. In this study, we found that this mouse model has decreased endogenous tau levels. Furthermore, this study demonstrates that FKPB51 colocalizes with pathological tau in the AD brain, and synergizes with Hsp90 to preserve tau from proteasomal degradation. Additionally, FKBP51 overexpression in mouse model of tau pathology leads to the preservation of tau. We went on to characterize this accumulated tau as being neurotoxic and oligomeric in nature, while being low in silver positive, β-sheet structure. In the human brain, we found that FKBP51 is strikingly increased with aging and even further in the AD brain. In support of these findings, we also found age-associated decreased methylation in the FKBP5 gene, which encodes FKBP51. Moreover, we found that increasing levels of FKBP51 caused other co-chaperone to have reduced Hsp90 binding and led to tau preservation. This supports a model where age-related increases in FKBP51 lead to the preservation of misfolded tau species and ultimately disease. In order to model the high FKBP51 expression found in the aging brain, we generated the first FKBP5 overexpressing mouse model, which is tet-regulatable. This mouse, rTgFKBP5, was made by targeted, single insertion of the human FKBP5 gene into the HIP11 locus of the mouse genome crossed with CamKIIα tTa mice. We have now confirmed high FKBP51 levels in the forebrain and hippocampus of this mouse, which will serve as a testing platform for FKBP51 regulating drugs. Overall, this work exemplifies FKBP51 as an important regulator of tau metabolism through Hsp90. With the absence of a negative phenotype in mice ablated of FKBP51 and the development of this novel, FKBP51 overexpressing mouse model, strategies designed to decrease FKPB51 levels or to disrupt the FKBP51/Hsp90 complex could be relevant for the treatment of tauopathies, like AD.

Childhood adversity is often associated with devastating physical, cognitive, and psychosocial outcomes, and is a major public health problem in terms of its prevalence and economic cost. Childhood adversity is associated with increased risk for psychopathology, as well as with dysregulation of the neurobiological stress response. An additional factor known to alter neuroendocrine functioning and increase psychopathology risk is polymorphisms within the FKBP5 gene. The goal of the current study was to examine the gene-environment interaction of childhood adversity and variation in the FKBP5 gene on the cortisol response to a psychosocial stress task (i.e., the Trier Social Stress Test). The final sample consisted of 90 depressed and non-depressed adolescents and young adults (11 - 21 years). Childhood adversity was assessed using the Childhood Experience and Abuse Scale (CECA; Bifulco et al., 1994), and was defined as the presence versus absence prior to 18 years of age of severe physical, sexual, or emotional abuse or neglect, witness to domestic discord/violence, or peer-perpetrated bullying. Participants were genotyped at the rs1360780 site of the FKBP5 gene and grouped according to whether they had at least one risk T allele (i.e., TT or TC genotype versus the CC genotype). Controlling for depression and anxiety psychopathology, I found a significant interaction of FKBP5 and childhood adversity status such that individuals with the FKBP5 risk allele (i.e., TT or TC genotype) and a history of childhood adversity showed a distinct cortisol response pattern characterized by decreasing cortisol from baseline and less cortisol output compared to individuals without childhood adversity. This relationship was specific to the experience of severe adversity and appeared to be strongest when adversity was defined as witnessing domestic discord/violence. These results are consistent with a diathesis-stress model in which the FKBP5 risk allele leaves individuals vulnerable to neurobiological dysregulation in the face of severe adverse experience in childhood. The implications of this research for understanding stress-related psychopathology and the limitations of this gene-environment interaction design are discussed. / Thesis (Master, Psychology) -- Queen's University, 2013-09-05 11:24:45.764

The elderly are at increased risk for developing psychiatric diseases, which include Alzheimer's disease, depression, anxiety and suicide. The probability of multiple disease comorbidity is also increased in the elderly. At the cellular level, the loss of protein homeostasis is often at the root of disease emergence, and thus the scientific community is searching for ways to help maintain this balance. A vast group of proteins that are paramount to balancing and counterbalancing protein levels is the molecular chaperone protein group, which has evolved a tremendous variety of functions in the cell. They aid in protein trafficking, folding, receptor signaling, neurotransmission, vesicle forming and fusion, protein degradation, and apoptosis, among other activities. Despite their best efforts, disease still ensues, but because of their vast number and multiple abilities, it may be possible to modulate these proteins as a way to treat and prevent disease. Chaperones are of particular interest in diseases of aging, because chaperone induction and effectiveness is reduced with age. In addition, many diseases of the elderly are brought on by aberrant protein accumulation, like Alzheimer's disease. As a result, the hypothesis of this dissertation is whether the modulation of molecular chaperones changes disease pathology. A molecular chaperone family that is important to protein degradation is the Hsp70 chaperone complex. Hsp70 proteins have specialized function depending on cell type and cellular compartment, but Hsp70 proteins are very important for protein synthesis and degradation. As a result, they are in a position to contribute to the regulation of proteins that become aberrant. In recent years scientific literature has indicated that compounds that inhibit the enzymatic ATP hydrolysis of these proteins promote tau degradation, which accumulates in Alzheimer's disease. Alzheimer's disease is the sixth leading cause of death in the U.S., it is a progressive neurodegenerative disease, and is caused by the aberrant accumulation of the amyloid beta and tau proteins. Here, we show that treatment with the Hsp70 inhibitor methylene blue, reduces tau, saves neurons, and restores cognition, in a mouse model of tau accumulation (rTg4510). Cognitive rescue occurred despite a severe tangle load, equal to control treated tau transgenic mice. This study shows that reducing soluble tau can restore cognition, reducing tangles is not necessarily to ameliorate cognition, and saving neurons is not sufficient to increase cognition if they are burdened with soluble tau. This work shows that methylene blue does not affect the the number of tau tangles in this model, as suggested by in vitro data. It also suggests that further work into the development of Hsp70 ATPase inhibitors may find success in alleviating the soluble tau burden found in Alzheimer's disease. The co-chaperone FKBP5 is also of extreme importance, not because it is essential, but because research has implicated this protein with a host of psychiatric diseases. Single nucleotide polymorphisms in this gene, which increase the levels of FKBP5, interact with averse traumatic events to enhance the likelihood of developing mood and anxiety disorders, including major depressive disorder, post-traumatic stress disorder, bipolar disorder, and suicide. Moreover, we have found that FKBP5 protein levels increase with age in the human brain, increasing the risk for the elderly of developing disease if exposed to traumatic stress. Here, we tested the hypothesis that FKBP5 negatively regulates resilient behavior. We found that FKBP5 levels increase with age in the wild type mouse brain, and that wild type mice display reduced resiliency with age. FKBP5-/- mice, on the other hand, show enhanced resiliency to stress at all ages tested, and are protected from aging-induced despair. At the molecular level, FKBP5 is a robust inhibitor of the glucocorticoid receptor, which is responsible for the shut-off of the hypothalamic-pituitary-adrenal axis. In addition, excess glucocorticoid levels in the blood is a robust marker of psychiatric disease. Consequently, FKBP5 may be causing disease through enhanced levels of glucocorticoids. FKBP5-/- mice display reduced corticosterone after stress. Moreover, corticosterone production increases with age, and FKBP5-/- mice are protected from this increase. These studies are the first to show that reducing the levels of FKBP5 is a promising therapeutic option for the treatment of mood disorders in the elderly, resiliency naturally declines with age due to FKBP5, corticosterone levels after stress rise due to FKBP5, and that the ablation of this gene increases resiliency and prevents aging- induced despair. As a whole, these data show that the modulation of chaperone proteins has the potential for developing new therapies for the treatment of psychiatric diseases of the elderly.

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