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The mechanically activated Piezo channel plays a versatile role in conferring mechanosensitivity to various cell types. However, how it incorporates its intrinsic mechanosensitivity and cellular components to effectively sense long-range mechanical perturbation across a cell remains elusive. Here we show that Piezo channels are biochemically and functionally tethered to the actin cytoskeleton via the cadherin-b-catenin mechanotransduction complex, whose perturbation significantly impairs Piezo-mediated responses. Mechanistically, the adhesive extracellular domain of E-cadherin interacts with the cap domain of Piezo1, which controls the transmembrane gate, while its cytosolic tail might interact with the cytosolic domains of Piezo1, which are in close proximity to its intracellular gates, allowing a direct focus of adhesion-cytoskeleton-transmitted force for gating. Specific disruption of the intermolecular interactions prevents cytoskeleton-dependent gating of Piezo1. Thus, we propose a force-from-filament model to complement the previously suggested force-from-lipids model for mechanogating of Piezo channels, enabling them to serve as versatile and tunable mechanotransducers.

The stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis is normally suppressed during pregnancy. Dysregulation of the HPA axis has been proposed to play a role in postpartum depression. However, direct investigation into the relationship between the HPA axis and postpartum depression has been hindered by the lack of useful animal models. Building on our discovery of a role for the K+/Cl-co-transporter, KCC2, in the GABAergic regulation of CRH neurons in the paraventricular nucleus of the hypothalamus (PVN), critical for mounting the body's physiological response to stress, we assessed the role of KCC2 in the regulation of the HPA axis during pregnancy and the postpartum period. Here we demonstrate that the normal suppression of the stress-induced activation of the HPA axis during the peripartum period involves maintenance of KCC2 in the PVN. Mice lacking KCC2 specifically in corticosterone-releasing hormone (CRH) neurons, which govern the activity of the HPA axis (KCC2/Crh mice), exhibit dysregulation of the HPA axis and abnormal postpartum behaviors. Loss of KCC2 specifically in CRH neurons in the PVN is sufficient to reproduce the depression-like phenotype and deficits in maternal behaviors during the postpartum period. Similarly, chemogenetic activation of CRH neurons in the PVN is sufficient to induce abnormal postpartum behaviors and chemogenetic silencing of CRH neurons in the PVN can ameliorate abnormal postpartum behaviors observed in KCC2/Crh mice. This study demonstrates that dysregulation of the HPA axis is sufficient to induce abnormal postpartum behaviors and deficits in maternal behaviors in mice, providing empirical support for a role of HPA axis dysfunction in the pathophysiology of postpartum depression.

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Running Title: A tether mechanism for mechanogating of the Piezo channel Highlights• Revealed biochemical and functional interactions between Piezo1 and the E-cadherin-β-catenin-F-actin mechanotransduction complex.• Identified critical mechanogating domains of Piezo1 as E-cadherin binding domains.• Specific disruption of the intermolecular interactions between Piezo1 and E-cadherin prevents cytoskeleton-dependent gating of Piezo1.• Proposed a tether model for mechanogating of Piezo channels.

HBP is an efficient intracellular delivery vehicle for trichosanthin and makes trichosanthin-HBP become a promising agent for cancer therapy.

Human-derived cell penetrating peptides (CPPs) have attracted much more attentions than other CPPs which are limited by their potential toxicity and immunogenicity. Previously, we identified a novel human-originated CPP (named heparin-binding domain (HBD) in this article), which derived from the C-terminus of human extracellular superoxide dismutase, and demonstrated HBD is an efficient vector for delivering exogenous drug molecules such as apoptin into HeLa cells. In this study, we found this novel CPP showed differentiated efficiency in several tested cell lines. Heparin competitive inhibition experiment and heparanase pre-incubation experiment showed cell surface polysaccharides play an important role for the transmembrane transport. The results of endocytosis inhibitors suggested that HBD penetrates the cell membrane via a direct translocation, which is different from that of TAT, a classical clathrin-mediated endocytosis. HBD could deliver up to 90 kD protein cargoes into cells. Different conjugated modes with cargo molecules greatly affect their translocation efficiency. HBD also showed significant nuclear transport capacity when it was incubated with HeLa cells. Furthermore, the core region for HBD possessing membrane-penetrating ability was identified by deletion analyses. These results would be helpful for developing HBD as a new nuclear delivery tool for therapeutic biomolecules.