Structure and function of the TPR-domain immunophilins FKBP51 and FKBP52 in normal physiology and disease

Regulation of tau by peptidyl-prolyl isomerases

Tau is an intrinsically disordered protein found abundantly in axons, where it binds to microtubules. Since tau is a central player in the dynamic microtubule network, it is highly regulated by post-translational modifications. Abnormal hyperphosphorylation and aggregation of tau characterize a group of diseases called tauopathies. A specific protein family of cis/trans peptidyl-prolyl isomerases (PPIases) can interact with tau to regulate its aggregation and neuronal resilience. Structural interactions between tau and specific PPIases have been determined, establishing possible mechanisms for tau regulation and modification. While there have been numerous in vivo studies evaluating the impact of PPIase expression on tau biology/pathology, the direct roles of PPIases have yet to be fully characterized. Different PPIases correlate to either increased or decreased levels of tau-associated degeneration. Therefore, the ability of PPIases to structurally modify and regulate tau should be further investigated due to its potential therapeutic implications for Alzheimer's disease and other tauopathies.

Tandem-repeat proteins conformational mechanics are optimized to facilitate functional interactions and complexations

The architectures of tandem-repeat proteins are distinct from those of globular proteins. Individual modules, each comprising small structural motifs of 20-40 residues, are arrayed in a quasi one-dimensional fashion to form striking, elongated, horseshoe-like, and superhelical architectures, stabilized solely by short-range interaction. The spring-like shapes of repeat arrays point to elastic modes of action, and these proteins function as adapter molecules or 'hubs,' propagating signals within multi-subunit assemblies in diverse biological contexts. This flexibility is apparent in the dramatic variability observed in the structures of tandem-repeat proteins in different complexes. Here, using computational analysis, we demonstrate the striking ability of just one or a few global motions to recapitulate these structures. These findings show how the mechanics of repeat arrays are robustly enabled by their unique architecture. Thus, the repeating architecture has been optimized by evolution to favor functional modes of motions. The global motions enabling functional transitions can be fully visualized at http://bahargroup.org/tr_web.

FKBP5 regulates trophoblast-macrophage crosstalk in recurrent spontaneous abortion through PI3K/AKT and NF-κB signaling pathways

FK506-binding protein 5 (FKBP5) contributes to many diseases; However, it remains unclear whether FKBP5 is relevant to recurrent spontaneous abortion (RSA) and the mechanisms by which it is involved in maternal-fetal immunological tolerance. Placental tissue was collected in women with normal pregnancy and RSA and examined for FKBP5 expression. Human trophoblast cell lines and THP-1-derived M0 macrophages were used to explore the role of FKBP5 in RSA and its mechanism. The role of FKBP5 on pregnancy outcomes was assessed using a mouse model of miscarriage. This study found that upregulation of FKBP5 at the placental interface is involved in the pathogenesis of RSA by depressing trophoblast function and promoting M1-type macrophage polarization. First, FKBP5 expression was upregulated in the villi of RSA, and FKBP5 regulated trophoblast function by inhibiting HAPLN1 expression through suppression of PI3K/AKT signaling. In addition, FKBP5 inhibited trophoblast IL-6 secretion by suppressing PI3K/AKT signaling, thereby promoting macrophage polarization toward the M1 phenotype. Meanwhile, FKBP5 was significantly elevated in decidual macrophages from patients with RSA and promoted M1 macrophage polarization via ROS/NF-κB signaling and further inhibited trophoblast function. Finally, FKBP5 inhibitors improved embryo resorption rate in miscarried mice. In conclusion, FKBP5 is essential in maintaining pregnancy and trophoblast-macrophage crosstalk in the maternal-fetal interface, which may be a potential target for diagnosing and treating RSA.