FKBP51-Hsp90 Interaction-Deficient Mice Exhibit Altered Endocrine Stress Response and Sex Differences Under High-Fat Diet.

FK506-binding protein 51 kDa (FKBP51), encoded by Fkbp5 gene, gained considerable attention as an important regulator of several aspects of human biology including stress response, metabolic dysfunction, inflammation, and age-dependent neurodegeneration. Its catalytic peptidyl-prolyl isomerase (PPIase) activity is mediated by the N-terminal FK506-binding (FK1) domain, whereas the C-terminal tetratricopeptide motif (TPR) domain is responsible for FKBP51 interaction with molecular chaperone heat shock protein 90 (Hsp90). To understand FKBP51-related biology, several mouse models have been created. These include Fkbp5 complete and conditional knockouts, overexpression, and humanized models. To dissect the role of FKBP51-Hsp90 interaction in FKBP51 biology, we have created an interaction-deficient mouse (Fkbp5TPRmut) by introducing two-point mutations in the TPR domain of FKBP51. FKBP51-Hsp90 interaction-deficient mice are viable, fertile and show Mendelian inheritance. Intracellular association of FKBP51 with Hsp90 is significantly reduced in homozygous mutants compared to wild-type animals. No behavioral differences between genotypes were seen at 2 months of age, however, sex-dependent differences were detected in Y-maze and fear conditioning tests at the age of 12 months. Moreover, we have found a significant reduction in plasma levels of corticosterone and adrenocorticotropic hormone in Fkbp5TPRmut mice after acute stress. In contrast to Fkbp5 knockout mice, females of Fkbp5TPRmut showed increased body weight gain under high-fat diet treatment. Our data confirm the importance of FKBP51-Hsp90 interactions for stress-related endocrine signaling. Also, Fkbp5TPRmut mice can serve as a useful in vivo tool to discriminate between Hsp90-dependent and independent functions of FKBP51.

From an Hsp90 - binding protein to a peptide drug.

The Lpl proteins represent a class of lipoproteins that was first described in the opportunistic bacterial pathogen Staphylococcus aureus, where they contribute to pathogenicity by enhancing F-actin levels of host epithelial cells and thereby increasing S. aureus internalization. The model Lpl protein, Lpl1 was shown to interact with the human heat shock proteins Hsp90α and Hsp90ß, suggesting that this interaction may trigger all observed activities. Here we synthesized Lpl1-derived peptides of different lengths and identified two overlapping peptides, namely, L13 and L15, which interacted with Hsp90α. Unlike Lpl1, the two peptides not only decreased F-actin levels and S. aureus internalization in epithelial cells but they also decreased phagocytosis by human CD14+ monocytes. The well-known Hsp90 inhibitor, geldanamycin, showed a similar effect. The peptides not only interacted directly with Hsp90α, but also with the mother protein Lpl1. While L15 and L13 significantly decreased lethality of S. aureus bacteremia in an insect model, geldanamycin did not. In a mouse bacteremia model L15 was found to significantly decreased weight loss and lethality. Although the molecular bases of the L15 effect is still elusive, in vitro data indicate that simultaneous treatment of host immune cells with L15 or L13 and S. aureus significantly increase IL-6 production. L15 and L13 represent not antibiotics but they cause a significant reduction in virulence of multidrug-resistant S. aureus strains in in vivo models. In this capacity, they can be an important drug alone or additive with other agents.

Novel complementary coloprotective effects of metformin and MCC950 by modulating HSP90/NLRP3 interaction and inducing autophagy in rats.

Ulcerative colitis (UC) is a chronic and relapsing inflammatory disorder, which has an increased incidence worldwide. The NLRP3 inflammasome has recently been assigned as a promising target for several inflammatory diseases including bowel inflammation. We aimed to investigate the potential complementary effects of combined therapy of metformin and MCC950 in dextran sodium sulfate (DSS)-induced colitis in rats. Metformin/MCC950 mitigated colon shortening, disease activity index (DAI), and macroscopic damage index (MDI). It also improved the colon histology picture and reduced the inflammation score. In addition, metformin/MCC950 augmented the antioxidant defense machinery and attenuated the myeloperoxidase (MPO) activity. Moreover, the levels of the pro-inflammatory mediators tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6) were reduced. This pharmacological activity might be attributed to interrupting the priming signal of the NLRP3 inflammasome activation through inactivating Toll-like receptor 4 (TLR4)/nuclear transcription factor kappa-B (NF-κB) signalling (effect of metformin) as well as interrupting the activation signal through potent inhibition of NLRP3 expression and caspase-1 (effect of MCC950). As a result, significant inhibition of the production of the bioactive IL-1ß and IL-18 occurred, and hence the pyroptosis process was inhibited. Moreover, the metformin/MCC950 leads to the induction of autophagy by AMP-activated protein kinase (AMPK)-dependent mechanisms leading to the accumulation of Beclin-1 and a substantial decline in the levels of p62 SQSTM1 (effect of metformin). The observed impeding effect on HSP90 along with inducing autophagy (effect of metformin) suggests that NLRP3 is prone to autophagic degradation. In conclusion, we reveal that the combination of metformin with MCC950 has a protective role in DSS-induced colitis and might become a candidate in a promising approach for the future treatment of human UC.