SKAP2-A Molecule at the Crossroads for Integrin Signalling and Immune Cell Migration and Function

Nicotine exposure is associated with targeted impairments in primordial follicle phenotype in cultured neonatal mouse ovaries

The ovarian reserve consists of a limited supply of primordial follicles (PFs), each containing an oocyte surrounded by a layer of granulosa cells (GCs). PFs are relatively quiescent and must remain viable for a long period, thereby making them susceptible to environmental and lifestyle influences. Given the widespread prevalence of e-cigarette use, this study aimed to investigate the effects of nicotine and its metabolite cotinine in a mouse model and to elucidate the mechanisms by which nicotine influences the ovarian reserve. Neonatal ovaries were cultured for 7-days in nicotine or cotinine reflective of concentrations in plasma of e-cigarette users. From histological evaluation, nicotine or cotinine had no impact on the number of PFs or early growing follicles; however, the medium (15 ng/ml) and high (45 ng/ml) concentrations of nicotine (but not cotinine) caused a small reduction in oocyte and GC size within PFs relative to controls (0 ng/ml; both P<0.01). These morphological effects were not associated with changes in immunofluorescent markers of apoptosis (active caspase-3) or proliferation (Pcna), but were associated with increased gH2AX in PF oocytes, indicative of DNA damage and repair. RNA-sequencing of cultured ovaries exposed to nicotine (45 ng/ml) relative to control (0 ng/ml), revealed a suite of differentially expressed candidates, as well as numerous gene ontology biological processes associated with increased DNA damage, metabolism, respiration and immune function, alongside suppression of meiosis, cell adhesion, differentiation and morphogenesis. Findings from this study indicate that direct nicotine exposure has a limited effect on the quantity of PFs, but importantly highlights a range of processes that could impinge on the quality of the ovarian reserve.

Role of DDR1 in Regulating MMPs in External Root Resorption

Human periodontal ligament cells (hPDLCs) express matrix metalloproteinases (MMPs), a group of enzymes responsible for the destruction of most extracellular matrix proteins in dental tissues, especially MMP-1, MMP-2, and MMP-13. Exploring the regulatory mechanism of MMPs is crucial for understanding external root resorption (ERR), one of the most severe complications, along with substantial loss of dental tissue, induced by trauma, pulpal infection, tooth bleaching, and orthodontic treatment, etc. Discoidin domain receptor 1 (DDR1), a cell surface receptor binding to collagen, has the potential to regulate the expression of MMP-1, MMP-2, and MMP-13, but the mechanism remains unclear. Thus, the present study aimed to investigate the connection and underlying mechanism between MMP-1, MMP-2, MMP-13, and DDR1 in hPDLCs. Our post-replantation ERR model revealed that Mmp-1, Mmp-2, Mmp-13, and Ddr1 all increased in the sites of ERR. hPDLCs with DDR1 knockdown exhibited a substantial reduction in MMP-1, MMP-2, and MMP-13 expression. To further confirm the underlying mechanism, we conducted further in vitro experiments, including RNA sequencing, RNA interference, RT-qPCR, Western blotting, and ELISA. Based on our results, MMP-1 was positively regulated by the Smad2/3 and MEK-ERK1/2 pathways and negatively regulated by the PI3K-Akt pathway through CCN2. MMP-2 and MMP-13 were positively regulated by the Smad2/3 pathway. MMP-13 was positively regulated by the MEK-ERK1/2 and PI3K/Akt signaling pathways. Collectively, DDR1 is a potent regulator of MMP-1, MMP-2, and MMP-13 expression through the Smad2/3, MEK-ERK1/2, and PI3K/Akt signaling pathways. Clarifying the significance and underlying mechanism by which DDR1 is involved in ERR might bring the chances to hinder the pathogenic process of ERR, hence reducing its incidence rate.

Drug repositioning for rosacea disease: Biological TARGET identification, molecular docking, pharmacophore mapping, and molecular dynamics analysis

Rosacea is a chronic dermatological condition that currently lacks a clear treatment approach due to an uncomprehensive knowledge of its pathogenesis. The main obstacle lies in understanding its etiology and the mode of action of the different drugs used. This study aims to clarify these aspects by employing drug repositioning. Using an in silico approach, we performed a transcriptomic analysis comparing samples from individuals with diverse types of rosacea to those from healthy controls to identify genes deregulated in this disease. Subsequently, we realized molecular docking and molecular dynamics studies to assess the binding affinity of drugs currently used to treat rosacea and drugs that target proteins interacting with, and thus affecting, proteins deregulated in rosacea. Our findings revealed that the downregulation of SKAP2 and upregulation of S100A7A in rosacea, could be involved in the pathogenesis of the disease. Furthermore, considering the drugs currently used for rosacea management, we demonstrated stable interactions between isotretinoin and BFH772 with SKAP2, and permethrin and PAC-14028 with S100A7A. Similarly, considering drugs targeting SKAP2 and S100A7A interactome proteins, we found that pitavastatin and dasatinib exert stable interactions with SKAP2, and lovastatin and tirbanibulin with S100A7A. In addition, we determine that the types of bonds involved in the interactions were different in SKAP2 from S100A7A. The drug-SKAP2 interactions are hydrogen bonds, whereas the drug-S100A7A interactions are of the hydrophobic type. In conclusion, our study provides evidence for the possible contribution of SKAP2 and S100A7A to rosacea pathology. Furthermore, it provides significant information on the molecular interactions between drugs and these proteins, highlighting the importance of considering structural features and binding interactions in the design of targeted therapies for skin disorders such as rosacea.

Plasma proteomics in children with new-onset type 1 diabetes identifies new potential biomarkers of partial remission

Partial remission (PR) occurs in only half of people with new-onset type 1 diabetes (T1D) and corresponds to a transient period characterized by low daily insulin needs, low glycemic fluctuations and increased endogenous insulin secretion. While identification of people with newly-onset T1D and significant residual beta-cell function may foster patient-specific interventions, reliable predictive biomarkers of PR occurrence currently lack. We analyzed the plasma of children with new-onset T1D to identify biomarkers present at diagnosis that predicted PR at 3 months post-diagnosis. We first performed an extensive shotgun proteomic analysis using Liquid Chromatography-Tandem-Mass-Spectrometry (LCMS/MS) on the plasma of 16 children with new-onset T1D and quantified 98 proteins significantly correlating with Insulin-Dose Adjusted glycated hemoglobin A1c score (IDAA1C). We next applied a series of both qualitative and statistical filters and selected protein candidates that were associated to pathophysiological mechanisms related to T1D. Finally, we translationally verified several of the candidates using single-shot targeted proteomic (PRM method) on raw plasma. Taken together, we identified plasma biomarkers present at diagnosis that may predict the occurrence of PR in a single mass-spectrometry run. We believe that the identification of new predictive biomarkers of PR and β-cell function is key to stratify people with new-onset T1D for β-cell preservation therapies.

Novel Factors Regulating Proliferation, Migration, and Differentiation of Fibroblasts, Keratinocytes, and Vascular Smooth Muscle Cells during Wound Healing

Chronic diabetic foot ulcers (DFUs) are a significant complication of diabetes mellitus, often leading to amputation, increased morbidity, and a substantial financial burden. Even with the advancements in the treatment of DFU, the risk of amputation still exists, and this occurs due to the presence of gangrene and osteomyelitis. Nonhealing in a chronic DFU is due to decreased angiogenesis, granulation tissue formation, and extracellular matrix remodeling in the presence of persistent inflammation. During wound healing, the proliferation and migration of fibroblasts, smooth muscle cells, and keratinocytes play a critical role in extracellular matrix (ECM) remodeling, angiogenesis, and epithelialization. The molecular factors regulating the migration, proliferation, and differentiation of these cells are scarcely discussed in the literature. The literature review identifies the key factors influencing the proliferation, migration, and differentiation of fibroblasts, keratinocytes, and vascular smooth muscle cells (VSMCs), which are critical in wound healing. This is followed by a discussion on the various novel factors regulating the migration, proliferation, and differentiation of these cells but not in the context of wound healing; however, they may play a role. Using a network analysis, we examined the interactions between various factors, and the findings suggest that the novel factors identified may play a significant role in promoting angiogenesis, granulation tissue formation, and extracellular matrix remodeling during wound healing or DFU healing. However, these interactions warrant further investigation to establish their role alone or synergistically.

SKAP2 acts downstream of CD11b/CD18 and regulates neutrophil effector function

Background

The importance of CD11b/CD18 expression in neutrophil effector functions is well known. Beyond KINDLIN3 and TALIN1, which are involved in the induction of the high-affinity binding CD11b/CD18 conformation, the signaling pathways that orchestrate this response remain incompletely understood.

Method

We performed an unbiased screening method for protein selection by biotin identification (BioID) and investigated the KINDLIN3 interactome. We used liquid chromatography with tandem mass spectrometry as a powerful analytical tool. Generation of NB4 CD18, KINDLIN3, or SKAP2 knockout neutrophils was achieved using CRISPR-Cas9 technology, and the cells were examined for their effector function using flow cytometry, live cell imaging, microscopy, adhesion, or antibody-dependent cellular cytotoxicity (ADCC).

Results

Among the 325 proteins significantly enriched, we identified Src kinase-associated phosphoprotein 2 (SKAP2), a protein involved in actin polymerization and integrin-mediated outside-in signaling. CD18 immunoprecipitation in primary or NB4 neutrophils demonstrated the presence of SKAP2 in the CD11b/CD18 complex at a steady state. Under this condition, adhesion to plastic, ICAM-1, or fibronectin was observed in the absence of SKAP2, which could be abrogated by blocking the actin rearrangements with latrunculin B. Upon stimulation of NB4 SKAP2-deficient neutrophils, adhesion to fibronectin was enhanced whereas CD18 clustering was strongly reduced. This response corresponded with significantly impaired CD11b/CD18-dependent NADPH oxidase activity, phagocytosis, and cytotoxicity against tumor cells.

Conclusion

Our results suggest that SKAP2 has a dual role. It may restrict CD11b/CD18-mediated adhesion only under resting conditions, but its major contribution lies in the regulation of dynamic CD11b/CD18-mediated actin rearrangements and clustering as required for cellular effector functions of human neutrophils.

Adaptor molecules mediate negative regulation of macrophage inflammatory pathways: a closer look

Macrophages play a central role in initiating, maintaining, and terminating inflammation. For that, macrophages respond to various external stimuli in changing environments through signaling pathways that are tightly regulated and interconnected. This process involves, among others, autoregulatory loops that activate and deactivate macrophages through various cytokines, stimulants, and other chemical mediators. Adaptor proteins play an indispensable role in facilitating various inflammatory signals. These proteins are dynamic and flexible modulators of immune cell signaling and act as molecular bridges between cell surface receptors and intracellular effector molecules. They are involved in regulating physiological inflammation and also contribute significantly to the development of chronic inflammatory processes. This is at least partly due to their involvement in the activation and deactivation of macrophages, leading to changes in the macrophages' activation/phenotype. This review provides a comprehensive overview of the 20 adaptor molecules and proteins that act as negative regulators of inflammation in macrophages and effectively suppress inflammatory signaling pathways. We emphasize the functional role of adaptors in signal transduction in macrophages and their influence on the phenotypic transition of macrophages from pro-inflammatory M1-like states to anti-inflammatory M2-like phenotypes. This endeavor mainly aims at highlighting and orchestrating the intricate dynamics of adaptor molecules by elucidating the associated key roles along with respective domains and opening avenues for therapeutic and investigative purposes in clinical practice.