Mitogen-activated protein kinase kinase kinase kinases (MAP4Ks) constitute a mammalian STE20-like serine/threonine kinase subfamily. Recent studies provide substantial evidence for MAP4K family kinases in the Hippo pathway regulation, suggesting a broad role of MAP4Ks in human physiology and diseases. However, a comprehensive analysis of the regulators and effectors for this key kinase family has not been fully achieved. Using a proteomic approach, we define the protein-protein interaction network for human MAP4K family kinases and reveal diverse cellular signaling events involving this important kinase family. Through it, we identify a STRIPAK complex component, STRN4, as a generic binding partner for MAP4Ks and a key regulator of the Hippo pathway in endometrial cancer development. Taken together, the results of our study not only generate a rich resource for further characterizing human MAP4K family kinases in numerous biological processes but also dissect the STRIPAK-mediated regulation of MAP4Ks in the Hippo pathway.

Beta-glucans, which existed in the cell walls of cereals, bacteria, and fungi, comprise a group of β-d-glucose polysaccharides. We investigated the effects of four kinds of beta-glucan, that are derived from barley, yeast, mushroom, and euglena on wound healing. The migration and viability of keratinocyte or fibroblast were analyzed using the in vitro scratch wound healing assay, invasion assay, MTT assay, and in vivo assay. All the beta-glucans had a significant effect on keratinocyte migration at 20 μM and showed no toxicity on dermal fibroblast. Moreover, treatment of keratinocytes with the beta-glucan derived from the mushroom (Schizophyllum commune) promoted in vivo wound closure. The Integrin/FAK/Src pathway is known to affect cell migration by forming lamellipodia. Beta-glucan from S. commune activates the Integrin/FAK/Src signaling pathway in a time-dependent. Reactive oxygen species are associated with fibroblast differentiation to contract dermal layer and synthesize collagens. We found that fibroblast was activated by increasing NOX4 expression. We propose that beta-glucan derived from mushroom is capable of promoting keratinocyte migration via the induction of FAK/Src phosphorylation there by accelerating wound closure and activating dermal fibroblast differentiation through NADPH oxidase for matrix remodeling.

Keratinocyte-fibroblast interactions are critical for skin repair after injury. During the proliferative phase of wound healing, proliferation, migration and differentiation of these cells are the major mechanisms leading to tissue remodeling. We have previously reported that glycitin, a major soy isoflavone, stimulates dermal fibroblast proliferation; and the phytochemical, 4′,6,7-trimethoxyisoflavone (TMF), induces migration of HaCaT keratinocyte cells. We therefore investigated whether these compounds display synergistic effects on skin cells during wound healing in vitro and in vivo. Co-treatment with TMF and glycitin synergistically promotes the proliferation and migration of both keratinocytes and dermal fibroblasts, with a 1:1 ratio of these compounds showing the greatest efficacy in our co-culture system. This keratinocyte-fibroblast interaction occurred via the secretion of TGF-β, and the induction of differentiation and proliferation was confirmed in both indirect and direct co-culture assays. In an excisional and burn wound animal model, mice treated with a 1:1 ratio of TMF and glycitin showed faster wound closure, regeneration and scar reduction than even the positive control drug. These data indicate that two isoflavones, TMF and glycitin, act synergistically to promote wound healing and anti-scarring and could potentially be developed together as a bioactive therapeutic for wound treatment.

The Hippo pathway is a central regulator of organ size and a key tumor suppressor via coordinating cell proliferation and death. Initially discovered in Drosophila, the Hippo pathway has been implicated as an evolutionarily conserved pathway in mammals; however, how this pathway was evolved to be functional from its origin is still largely unknown. In this study, we traced the Hippo pathway in premetazoan species, characterized the intrinsic functions of its ancestor components, and unveiled the evolutionary history of this key signaling pathway from its unicellular origin. In addition, we elucidated the paralogous gene history for the mammalian Hippo pathway components and characterized their cancer-derived somatic mutations from an evolutionary perspective. Taken together, our findings not only traced the conserved function of the Hippo pathway to its unicellular ancestor components, but also provided novel evolutionary insights into the Hippo pathway organization and oncogenic alteration.