Heat shock protein 70 (Hsp70) is a molecular chaperone that plays critical roles in protein homeostasis. Hsp70's chaperone activity is coordinated by intra-molecular interactions between its two ...domains, as well as inter-molecular interactions between Hsp70 and its co-chaperones. Each of these contacts represents a potential opportunity for the development of chemical inhibitors. To illustrate this concept, we review three classes of recently identified molecules that bind distinct pockets on Hsp70. Although all three compounds share the ability to interrupt core biochemical functions of Hsp70, they stabilize different conformers. Accordingly, each compound appears to interrupt a specific subset of inter- and intra-molecular interactions. Thus, an accurate definition of an Hsp70 inhibitor may require a particularly detailed understanding of the molecule's binding site and its effects on protein-protein interactions.
The fungal kingdom includes at least 6 million eukaryotic species and is remarkable with respect to its profound impact on global health, biodiversity, ecology, agriculture, manufacturing, and ...biomedical research. Approximately 625 fungal species have been reported to infect vertebrates, 200 of which can be human associated, either as commensals and members of our microbiome or as pathogens that cause infectious diseases. These organisms pose a growing threat to human health with the global increase in the incidence of invasive fungal infections, prevalence of fungal allergy, and the evolution of fungal pathogens resistant to some or all current classes of antifungals. More broadly, there has been an unprecedented and worldwide emergence of fungal pathogens affecting animal and plant biodiversity. Approximately 8,000 species of fungi and Oomycetes are associated with plant disease. Indeed, across agriculture, such fungal diseases of plants include new devastating epidemics of trees and jeopardize food security worldwide by causing epidemics in staple and commodity crops that feed billions. Further, ingestion of mycotoxins contributes to ill health and causes cancer. Coordinated international research efforts, enhanced technology translation, and greater policy outreach by scientists are needed to more fully understand the biology and drivers that underlie the emergence of fungal diseases and to mitigate against their impacts. Here, we focus on poignant examples of emerging fungal threats in each of three areas: human health, wildlife biodiversity, and food security.
Zygomycete fungi were classified as a single phylum, Zygomycota, based on sexual reproduction by zygospores, frequent asexual reproduction by sporangia, absence of multicellular sporocarps, and ...production of coenocytic hyphae, all with some exceptions. Molecular phylogenies based on one or a few genes did not support the monophyly of the phylum, however, and the phylum was subsequently abandoned. Here we present phylogenetic analyses of a genome-scale data set for 46 taxa, including 25 zygomycetes and 192 proteins, and we demonstrate that zygomycetes comprise two major clades that form a paraphyletic grade. A formal phylogenetic classification is proposed herein and includes two phyla, six subphyla, four classes and 16 orders. On the basis of these results, the phyla Mucoromycota and Zoopagomycota are circumscribed. Zoopagomycota comprises Entomophtoromycotina, Kickxellomycotina and Zoopagomycotina; it constitutes the earliest diverging lineage of zygomycetes and contains species that are primarily parasites and pathogens of small animals (e.g. amoeba, insects, etc.) and other fungi, i.e. mycoparasites. Mucoromycota comprises Glomeromycotina, Mortierellomycotina, and Mucoromycotina and is sister to Dikarya. It is the more derived clade of zygomycetes and mainly consists of mycorrhizal fungi, root endophytes, and decomposers of plant material. Evolution of trophic modes, morphology, and analysis of genome-scale data are discussed.
The major classes of molecular chaperones have highly variable sequences, sizes, and shapes, yet they all bind to unfolded proteins, limit their aggregation, and assist in their folding. Despite the ...central importance of this process to protein homeostasis, it has not been clear exactly how chaperones guide this process or whether the diverse families of chaperones use similar mechanisms. For the first time, recent advances in NMR spectroscopy have enabled detailed studies of how unfolded, “client” proteins interact with both ATP-dependent and ATP-independent classes of chaperones. Here, we review examples from four distinct chaperones, Spy, Trigger Factor, DnaK, and HscA-HscB, highlighting the similarities and differences between their mechanisms. One striking similarity is that the chaperones all bind weakly to their clients, such that the chaperone–client interactions are readily outcompeted by stronger, intra- and intermolecular contacts in the folded state. Thus, the relatively weak affinity of these interactions seems to provide directionality to the folding process. However, there are also key differences, especially in the details of how the chaperones release clients and how ATP cycling impacts that process. For example, Spy releases clients in a largely folded state, while clients seem to be unfolded upon release from Trigger Factor or DnaK. Together, these studies are beginning to uncover the similarities and differences in how chaperones use weak interactions to guide protein folding.
Dysregulation of neuronal excitability underlies the pathogenesis of tauopathies, including frontotemporal dementia (FTD) with tau inclusions. A majority of FTD-causing tau mutations are located in ...the microtubule-binding domain, but how these mutations alter neuronal excitability is largely unknown. Here, using CRISPR/Cas9-based gene editing in human pluripotent stem cell (iPSC)-derived neurons and isogenic controls, we show that the FTD-causing V337M tau mutation impairs activity-dependent plasticity of the cytoskeleton in the axon initial segment (AIS). Extracellular recordings by multi-electrode arrays (MEAs) revealed that the V337M tau mutation in human neurons leads to an abnormal increase in neuronal activity in response to chronic depolarization. Stochastic optical reconstruction microscopy of human neurons with this mutation showed that AIS plasticity is impaired by the abnormal accumulation of end-binding protein 3 (EB3) in the AIS submembrane region. These findings expand our understanding of how FTD-causing tau mutations dysregulate components of the neuronal cytoskeleton, leading to network dysfunction.
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•The FTD-causing V337M tau mutation impairs axon initial segment (AIS) plasticity•The V337M tau mutation impairs activity homeostasis•The V337M tau mutation leads to accumulation of EB3 in the AIS•EB3 is critical for regulating AIS plasticity and activity homeostasis
Frontotemporal dementia (FTD) with tau pathology is associated with aberrant hyperexcitability of neuronal networks. In human iPSC-derived neurons, Sohn et al. demonstrates that FTD-causing tau mutation abolishes activity-dependent plasticity of the axon initial segment and impairs homeostasis of neuronal activity via impacting AIS cytoskeleton, resulting in dysregulation of neuronal network function.
•The Insomnia Coach mobile app is a scalable, self-guided method to deliver CBT-I.•Veterans with insomnia symptoms found the app feasible and acceptable to use.•Insomnia Coach showed improvements on ...select sleep and mental health symptoms.
Insomnia is highly prevalent among military veterans but access to cognitive-behavioral therapy for insomnia (CBT-I) is limited. Thus, this study examined the feasibility, acceptability, and potential efficacy of Insomnia Coach, a CBT-I-based, free, self-management mobile app. Fifty U.S. veterans, who were mostly male (58%) and mean age 44.5 (range = 28–55) years with moderate insomnia symptoms were randomized to Insomnia Coach (n = 25) or a wait-list control condition (n = 25) for 6 weeks. Participants completed self-report measures and sleep diaries at baseline, posttreatment, and follow-up (12 weeks postrandomization), and app participants (n = 15) completed a qualitative interview at posttreatment. Findings suggest that Insomnia Coach is feasible to use, with three quarters of participants using the app through 6 weeks and engaging with active elements. For acceptability, perceptions of Insomnia Coach were very favorable based on both self-report and qualitative interview responses. Finally, for potential efficacy, at posttreatment, a larger proportion of Insomnia Coach (28%) than wait-list control participants (4%) achieved clinically significant improvement (p = .049) and there was a significant treatment effect on daytime sleep-related impairment (d = −0.6, p = .044). Additional treatment effects emerged at follow-up for insomnia severity (d = −1.1, p = .001), sleep onset latency (d = −0.6, p = .021), global sleep quality (d = −0.9, p = .002), and depression symptoms (d = −0.8, p = .012). These findings provide preliminary evidence that among veterans with moderate insomnia symptoms, a CBT-I-based self-management app is feasible, acceptable, and promising for improving insomnia severity and other sleep-related outcomes. Given the vast unmet need for insomnia treatment in the population, Insomnia Coach may provide an easily accessible, convenient public health intervention for individuals not receiving care.
Legionella pneumophila (L.p.), the microbe responsible for Legionnaires’ disease, secretes ∼300 bacterial proteins into the host cell cytosol. A subset of these proteins affects a wide range of ...post-translational modifications (PTMs) to disrupt host cellular pathways. L.p. has 5 conserved eukaryotic-like Ser/Thr effector kinases, LegK1–4 and LegK7, which are translocated during infection. Using a chemical genetic screen, we identified the Hsp70 chaperone family as a direct host target of LegK4. Phosphorylation of Hsp70s at T495 in the substrate-binding domain disrupted Hsp70’s ATPase activity and greatly inhibited its protein folding capacity. Phosphorylation of cytosolic Hsp70 by LegK4 resulted in global translation inhibition and an increase in the amount of Hsp70 on highly translating polysomes. LegK4’s ability to inhibit host translation via a single PTM uncovers a role for Hsp70 in protein synthesis and directly links it to the cellular translational machinery.
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•Legionella kinase 4 (LegK4) phosphorylates host cytosolic Hsp70s during infection•Phosphorylated Hsp70 has reduced ATPase and refolding activity•LegK4 inhibits host translation via Hsp70 phosphorylation•LegK4 increases the amount of Hsp70 associated with translating polysomes
Moss et al. describe an example of a bacterial pathogen effector modifying host Hsp70 to achieve translational inhibition. The Legionella pneumophila kinase LegK4 phosphorylates a conserved threonine on Hsp70 to reduce the chaperone’s refolding capacity and inhibit cellular protein translation.
Human evolutionary scholars have long supposed that the earliest stone tools were made by the genus Homo and that this technological development was directly linked to climate change and the spread ...of savannah grasslands. New fieldwork in West Turkana, Kenya, has identified evidence of much earlier hominin technological behaviour. We report the discovery of Lomekwi 3, a 3.3-million-year-old archaeological site where in situ stone artefacts occur in spatiotemporal association with Pliocene hominin fossils in a wooded palaeoenvironment. The Lomekwi 3 knappers, with a developing understanding of stone's fracture properties, combined core reduction with battering activities. Given the implications of the Lomekwi 3 assemblage for models aiming to converge environmental change, hominin evolution and technological origins, we propose for it the name 'Lomekwian', which predates the Oldowan by 700,000 years and marks a new beginning to the known archaeological record.
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