Tyrosine phosphatase SHP2 negatively regulates NLRP3 inflammasome activation via ANT1-dependent mitochondrial homeostasis

Integrated in silico MS-based phosphoproteomics and network enrichment analysis of RASopathy proteins

Background

RASopathies are a group of syndromes showing clinical overlap caused by mutations in genes affecting the RAS-MAPK pathway. Consequent disruption on cellular signaling leads and is driven by phosphoproteome remodeling. However, we still lack a comprehensive picture of the different key players and altered downstream effectors.

Methods

An in silico interactome of RASopathy proteins was generated using pathway enrichment analysis/STRING tool, including identification of main hub proteins. We also integrated phosphoproteomic and immunoblotting studies using previous published information on RASopathy proteins and their neighbors in the context of RASopathy syndromes. Data from Phosphosite database (www.phosphosite.org) was collected in order to obtain the potential phosphosites subjected to regulation in the 27 causative RASopathy proteins. We compiled a dataset of dysregulated phosphosites in RASopathies, searched for commonalities between syndromes in harmonized data, and analyzed the role of phosphorylation in the syndromes by the identification of key players between the causative RASopathy proteins and the associated interactome.

Results

In this study, we provide a curated data set of 27 causative RASopathy genes, identify up to 511 protein–protein associations using pathway enrichment analysis/STRING tool, and identify 12 nodes as main hub proteins. We found that a large group of proteins contain tyrosine residues and their biological processes include but are not limited to the nervous system. Harmonizing published RASopathy phosphoproteomic and immunoblotting studies we identified a total of 147 phosphosites with increased phosphorylation, whereas 47 have reduced phosphorylation. The PKB signaling pathway is the most represented among the dysregulated phosphoproteins within the RASopathy proteins and their neighbors, followed by phosphoproteins implicated in the regulation of cell proliferation and the MAPK pathway.

Conclusions

This work illustrates the complex network underlying the RASopathies and the potential of phosphoproteomics for dissecting the molecular mechanisms in these syndromes. A combined study of associated genes, their interactome and phosphorylation events in RASopathies, elucidates key players and mechanisms to direct future research, diagnosis and therapeutic windows.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01934-x.

Preservation of mitochondrial homeostasis is responsible for the ameliorative effects of Suhuang antitussive capsule on non-resolving inflammation via inhibition of NF-κB signaling and NLRP3 inflammasome activation

ETHNOPHARMACOLOGICAL RELEVANCE

Suhuang antitussive capsule (Suhuang), one of traditional antitussive Chinese patent medicines, has been used for the treatment of post-infectious cough and cough variant asthma in clinical practice. It has been demonstrated to show numerous biological actions including antitussive and anti-inflammatory effects.

AIM OF THE STUDY

This study aims to investigate the effects of Suhuang on non-resolving inflammation and its underlying molecular mechanism.

MATERIAL AND METHODS

In vitro, mitochondrial membrane potential and ROS were detected by flow cytometry analysis. mtDNA release and mPTP fluorescence were determined by Q-PCR and fluorescence microplate reader analysis. Cytochrome C release and 8-OHdG levels were evaluated by ELISA. Additionally, the effects of Suhuang on Drp1, MMP9, IκBα/NF-κB and NLRP3/ASC/Caspase-1 expression were determined by Q-PCR, gelatin zymography or immunoblot analysis. In vivo, C57/BL6 mice were orally administrated for 2 weeks with Suhuang, then lung injury was induced by LPS. Inflammatory mediators mRNA, histological assessment and NF-κB/Caspase-1/IL-1β levels were evaluated by Q-PCR, H&E staining and immunoblot analysis. Two sepsis models of mice were further used to evaluate its anti-inflammatory effects.

RESULTS

Suhuang restored mitochondrial homeostasis by inhibiting Drp1 activation and mitochondrial fission. Besides, Suhuang reduced mPTP opening, mitochondrial membrane potential collapse, ROS overproduction and mtDNA release. Moreover, Suhuang down-regulated MMP9 expression. As a consequence of preserved mitochondrial homeostasis, Suhuang inhibited NF-κB pathway activation by prevention of NF-κB-p65 phosphorylation and IκBα degradation. Suhuang also limited NLRP3 inflammasome activation by blocking NLRP3-ASC interaction and promoting NLRP3 ubiquitination degradation. Drp1 knockdown in vitro diminished the inhibitory effects of Suhuang on inflammatory responses, indicating the essential role of Drp1 in the Suhuang's activity. Consistently, the therapeutic effects of Suhuang were confirmed in LPS-inhaled mice, which recapitulated the protective actions of Suhuang in mitochondrial homeostasis in vitro. Additionally, two sepsis models of mice confirmed the inhibitory effects of Suhuang on uncontrolled inflammation.

CONCLUSIONS

Altogether, our work reveals that Suhuang inhibits non-resolving inflammation through inhibition of NF-κB signaling and NLRP3 inflammasome activation by preserving mitochondrial homeostasis, providing new pharmacological data for the clinical use of Suhuang. Our study also suggests mitochondrial homeostasis as a potential intrinsic regulatory strategy for treating inflammatory diseases.

SHP2 drives inflammation-triggered insulin resistance by reshaping tissue macrophage populations

Insulin resistance is a key event in type 2 diabetes onset and a major comorbidity of obesity. It results from a combination of fat excess-triggered defects, including lipotoxicity and metaflammation, but the causal mechanisms remain difficult to identify. Here, we report that hyperactivation of the tyrosine phosphatase SHP2 found in Noonan syndrome (NS) led to an unsuspected insulin resistance profile uncoupled from altered lipid management (for example, obesity or ectopic lipid deposits) in both patients and mice. Functional exploration of an NS mouse model revealed this insulin resistance phenotype correlated with constitutive inflammation of tissues involved in the regulation of glucose metabolism. Bone marrow transplantation and macrophage depletion improved glucose homeostasis and decreased metaflammation in the mice, highlighting a key role of macrophages. In-depth analysis of bone marrow-derived macrophages in vitro and liver macrophages showed that hyperactive SHP2 promoted a proinflammatory phenotype, modified resident macrophage homeostasis, and triggered monocyte infiltration. Consistent with a role of SHP2 in promoting inflammation-driven insulin resistance, pharmaceutical SHP2 inhibition in obese diabetic mice improved insulin sensitivity even better than conventional antidiabetic molecules by specifically reducing metaflammation and alleviating macrophage activation. Together, these results reveal that SHP2 hyperactivation leads to inflammation-triggered metabolic impairments and highlight the therapeutical potential of SHP2 inhibition to ameliorate insulin resistance.

SHP2-Mediated Inhibition of DNA Repair Contributes to cGAS-STING Activation and Chemotherapeutic Sensitivity in Colon Cancer

As a cytoplasmic sensor of double-stranded DNA (dsDNA), the cyclic GMP-AMP synthase-stimulator of IFN genes (STING) pathway plays an important role in antitumor immunity. In this study, we investigated the effect of Src homology-2 domain-containing protein tyrosine phosphatase-2 (SHP2) on tumor cell-intrinsic STING pathway activity and DNA repair in colon cancer. SHP2 interacted with and dephosphorylated PARP1 after DNA damage. PARP1 inhibition by SHP2 resulted in reduced DNA repair and accumulation of dsDNA in cells, thus promoting hyperactivation of the STING pathway. The SHP2 agonist lovastatin was able to enhance SHP2 activity and promote STING pathway activation. Moreover, lovastatin significantly enhanced the efficacy of chemotherapy in colon cancer models, in part via STING pathway-mediated antitumor immunity. These findings suggest that SHP2 exacerbates STING pathway activation by restricting PARP1-mediated DNA repair in tumor cells, providing a basis for the combined use of lovastatin and chemotherapy in the treatment of colon cancer. SIGNIFICANCE: Dephosphorylation of PARP1 by SHP2 simultaneously suppresses DNA repair and enhances STING pathway-mediated antitumor immunity, highlighting SHP2 activation as a potential therapeutic approach in colon cancer.

Curcumin analogue AI-44 alleviates MSU-induced gouty arthritis in mice via inhibiting cathepsin B-mediated NLRP3 inflammasome activation

NOD-like receptors (NLRs), as a part of intracellular pattern recognition receptors (PRR), are important regulators in innate immune system. The NLRP3 inflammasome which is a member of NLRs has been linked to several human inflammatory diseases. Gouty arthritis is triggered when the deposition of monosodium urate (MSU) crystals in joints induces acute inflammation characterized by the recruitment of macrophages and neutrophils. In this study, we explored the curcumin analogue AI-44 alleviated the gouty arthritis in mice via suppressing MSU engaging NLRP3 inflammasome activation. Furthermore, we demonstrated that AI-44 inhibited the interaction of cathepsin B and NLRP3 to prevent the activation of NLRP3 inflammasome. Moreover, we found AI-44 inhibited the enzyme activity of cathepsin B and bound to the key residue E122 in cytoplasm but not in lysosome. Collectively, these data suggest that AI-44 is a novel drug candidate for the treatment of gouty arthritis through targeting cathepsin B and inhibiting NLRP3 inflammasome activation.

Metabolic ROS Signaling: To Immunity and Beyond

Metabolism is a critical determinant of immune cell functionality. Immunometabolism, by definition, is a multidisciplinary area of immunology research that integrates the knowledge of energy transduction mechanisms and biochemical pathways. An important concept in the field is metabolic switch, a transition of immune cells upon activation to preferential utilization of select catabolic pathways for their energy needs. Mitochondria are not inert in this process and contribute to the metabolic adaptation by different mechanisms which include increasing ATP production to match dynamic bioenergetic demands and serving as a signaling platform. The latter involves generation of reactive oxygen species (ROS), one of the most intensively studied mitochondrial processes. While the role of mitochondrial ROS in the context of oxidative stress is well established, ROS signaling in immunity is an emerging and quickly changing field. In this review, we discuss ROS signaling and immunometabolism concepts from the standpoint of bioenergetics. We also provide a critical insight into the methodology for ROS assessment, outlining current challenges in the field. Finally, based on our analysis of the literature data, we hypothesize that regulatory ROS production, as opposed to oxidative stress, is controlled by mitochondrial biogenesis rather than metabolic switches.

Activating Mutation of SHP2 Establishes a Tumorigenic Phonotype Through Cell-Autonomous and Non-Cell-Autonomous Mechanisms

Gain-of-function mutation of SHP2 is a central regulator in tumorigenesis and cancer progression through cell-autonomous mechanisms. Activating mutation of SHP2 in microenvironment was identified to promote cancerous transformation of hematopoietic stem cell in non-autonomous mechanisms. It is interesting to see whether therapies directed against SHP2 in tumor or microenvironmental cells augment antitumor efficacy. In this review, we summarized different types of gain-of-function SHP2 mutations from a human disease. In general, gain-of-function mutations destroy the auto-inhibition state from wild-type SHP2, leading to consistency activation of SHP2. We illustrated how somatic or germline mutation of SHP2 plays an oncogenic role in tumorigenesis, stemness maintenance, invasion, etc. Moreover, the small-molecule SHP2 inhibitors are considered as a potential strategy for enhancing the efficacy of antitumor immunotherapy and chemotherapy. We also discussed the interconnection between phase separation and activating mutation of SHP2 in drug resistance of antitumor therapy.

Targeting SHP2 as a therapeutic strategy for inflammatory diseases

With the change of lifestyle and the acceleration of aging process, inflammatory diseases have increasingly become one of the most vital threats to global human health. SHP2 protein is a non-receptor tyrosine phosphatase encoded by PTPN11 gene, and it is widely expressed in various tissues and cells. Numerous studies have shown that SHP2 plays important roles in the regulation of inflammatory diseases, including cancer-related inflammation, neurodegenerative diseases and metabolic diseases. In this paper, the roles of SHP2 in inflammatory diseases of various physiological systems were reviewed. At the same time, the latest SHP2 inhibitors were summarized, which will hold a promise for the therapeutic potential in future.

Polyphyllin D Shows Anticancer Effect through a Selective Inhibition of Src Homology Region 2-Containing Protein Tyrosine Phosphatase-2 (SHP2)

Natural products have continued to offer tremendous opportunities for drug development, as they have long been used in traditional medicinal systems. SHP2 has served as an anticancer target. To identify novel SHP2 inhibitors with potential anticancer activity, we screened a library containing 658 natural products. Polyphyllin D was found to selectively inhibit SHP2 over SHP1, whereas two other identified compounds (echinocystic acid and oleanolic acid) demonstrated dual SHP1 and SHP2 inhibition. In a cell-based assay, polyphyllin D exhibited cytotoxicity in Jurkat cells, an acute lymphoma leukemia cell line, whereas the other two compounds were ineffective. Polyphyllin D also decreased the level of phosphorylated extracellular signal-regulated kinase (p-ERK), a proliferation marker in Jurkat cells. Furthermore, knockdown of protein tyrosine phosphatase (PTP)N6 (SHP1) or PTPN11 (SHP2) decreased p-ERK levels. However, concurrent knockdown of PTPN6 and PTPN11 in Jurkat cells recovered p-ERK levels. These results demonstrated that polyphyllin D has potential anticancer activity, which can be attributed to its selective inhibition of SHP2 over SHP1.

Regulation of the NLRP3 Inflammasome by Post-Translational Modifications and Small Molecules

Inflammation is a host protection mechanism that eliminates invasive pathogens from the body. However, chronic inflammation, which occurs repeatedly and continuously over a long period, can directly damage tissues and cause various inflammatory and autoimmune diseases. Pattern recognition receptors (PRRs) respond to exogenous infectious agents called pathogen-associated molecular patterns and endogenous danger signals called danger-associated molecular patterns. Among PRRs, recent advancements in studies of the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome have established its significant contribution to the pathology of various inflammatory diseases, including metabolic disorders, immune diseases, cardiovascular diseases, and cancer. The regulation of NLRP3 activation is now considered to be important for the development of potential therapeutic strategies. To this end, there is a need to elucidate the regulatory mechanism of NLRP3 inflammasome activation by multiple signaling pathways, post-translational modifications, and cellular organelles. In this review, we discuss the intracellular signaling events, post-translational modifications, small molecules, and phytochemicals participating in the regulation of NLRP3 inflammasome activation. Understanding how intracellular events and small molecule inhibitors regulate NLRP3 inflammasome activation will provide crucial information for elucidating the associated host defense mechanism and the development of efficient therapeutic strategies for chronic diseases.

Tyrosine phosphatase SHP2 inhibitors in tumor-targeted therapies

Src homology containing protein tyrosine phosphatase 2 (SHP2) represents a noteworthy target for various diseases, serving as a well-known oncogenic phosphatase in cancers. As a result of the low cell permeability and poor bioavailability, the traditional inhibitors targeting the protein tyrosine phosphate catalytic sites are generally suffered from unsatisfactory applied efficacy. Recently, a particularly large number of allosteric inhibitors with striking inhibitory potency on SHP2 have been identified. In particular, few clinical trials conducted have made significant progress on solid tumors by using SHP2 allosteric inhibitors. This review summarizes the development and structure–activity relationship studies of the small-molecule SHP2 inhibitors for tumor therapies, with the purpose of assisting the future development of SHP2 inhibitors with improved selectivity, higher oral bioavailability and better physicochemical properties.

P2X7 receptor and the NLRP3 inflammasome: Partners in crime

Adenosine triphosphate (ATP) is a molecule that on one hand plays a central role in cellular energetics and which on the other is a ubiquitous signaling molecule when released into the extracellular media. Extracellular ATP accumulates in inflammatory environments where it acts as a damage-associated molecular pattern and activates the purinergic P2X receptor 7 (P2X7) in immune cells. P2X7 receptor activation induces the formation of the nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing 3 (NLRP3) inflammasome and the activation of the inflammatory caspase-1. Caspase-1 causes an inflammatory type of cell death called pyroptosis through the release of pro-inflammatory cytokines and intracellular content. Consequently, intense research efforts have been devoted to the design of novel anti-inflammatory therapies, focusing in particular on the P2X7 receptor and the NLRP3 pathway and the introduction of new blocking molecules in early phase clinical trials.

ANTs and cancer: Emerging pathogenesis, mechanisms, and perspectives

Adenine nucleotide translocases (ANTs) are a class of transporters located in the inner mitochondrial membrane that not only couple processes of cellular productivity and energy expenditure, but are also involved in the composition of the mitochondrial membrane permeability transition pore (mPTP). The function of ANTs has been found to be most closely related to their own conformational changes. Notably, as multifunctional proteins, ANTs play a key role in oncogenesis, which provides building blocks for tumor anabolism, control oxidative phosphorylation and glycolysis homeostasis, and govern cell death. Thus, ANTs constitute promising targets for the development of novel anticancer agents. Here, we review the recent findings regarding ANTs and their important mechanisms in cancer, with a focus on the therapeutic potential of targeting ANTs for cancer therapy.

Specific inhibition of SHP2 suppressed abdominal aortic aneurysm formation in mice by augmenting the immunosuppressive function of MDSCs

AIMS

To address the roles of SHP2 in regulating angiotensin II (Ang II) induced abdominal aortic aneurysm (AAA) and the potential molecular mechanisms.

MAIN METHODS

AAA model was established in apolipoprotein E-deficient (apoE^-/-) mice infused with Ang II. Suprarenal aortic luminal diameters were ultrasonically measured to determine the presentation of AAA in mice. The inflammatory and immunosuppressive factors in serum were detected by ELISA. AAA lesion size, positive macrophages and elastic laminae degradation were examined by histological analysis. Myeloid-derived suppressor cells (MDSCs) were measured by flow cytometry after magnetic bead sorting. Bioinformatics analysis was applied to screen the crucial genes related the progression of AAA.

KEY FINDINGS

Treatment with PHPS1 (SHP2 inhibitor) significantly decreased the vascular diameter of AAA. Histological analysis showed that PHPS1 obviously reduced the Masson positive area, macrophages positive area, as well as the damage rate of elastic laminae. Moreover, PHPS1 suppressed the expression of INF-γ, TNF-α and MMPs, as well as elevated IL-10 and arginase-1 expression. Additionally, PHPS1 enhanced the expression of granulocytic MDSCs (G-MDSCs). By consulting with bioinformatics, STAT3 was selected. In G-MDSCs, PHPS1 stimulation obviously increased the phosphorylation level of STAT3, as well as elevated the protein expression of C/EBPβ and arginase-1. However, the above phenomena can be blocked after Stattic (STAT3 inhibitor) treatment.

SIGNIFICANCE

SHP2 may affect the AAA progression by interfering with expansion and function of MDSCs to regulate the body immunity, which might afford a novel direction for the treatment of patients with AAA.

Therapeutic Potential of Apatinib Against Colorectal Cancer by Inhibiting VEGFR2-Mediated Angiogenesis and β-Catenin Signaling

Purpose

Apatinib is an inhibitor of VEGFR2 (vascular endothelial growth factor receptor 2) that has attracted a great deal of attention due to its promotion of anticancer activity. In the present study, we investigated the therapeutic effects of apatinib against colorectal cancer (CRC) and examined the underlying mechanism.

Materials and Methods

Both in vivo and in vitro assays were conducted to study the effect of apatinib on CRC. To elucidate the associated mechanism, RNA-seq (transcriptome) analysis was conducted on apatinib-treated HCT116 cells.

Results

Apatinib showed antiproliferative and proapoptotic effects, induced G0/G1 arrest and blocked cell migration and invasion in CRC. An analysis of the mechanism associated with apatinib activity demonstrated that by interacting with VEGFR2, apatinib decreased p-Src, p-Akt, and p-GSK3β levels, which further increased β-catenin ubiquitination and reduced the nuclear translocation of β-catenin. Furthermore, apatinib strongly suppressed CT26 cell growth in mouse xenograft models by inhibiting β-catenin signaling and angiogenesis.

Conclusion

Overall, the results of the present study here indicated that by inhibiting the VEGFR2-β-catenin-mediated malignant phenotype, apatinib significantly suppresses the growth of CRC, suggesting that the use of apatinib is a promising therapeutic strategy for CRC.

Mitochondria and T2D: Role of Autophagy, ER Stress, and Inflammasome

Type 2 diabetes (T2D) is one of the main current threats to human health. Both T2D and its numerous clinical complications are related to mitochondrial dysfunction and oxidative stress. Over the past decade, great progress has been made in extending our knowledge about the signaling events regulated by mitochondria. However, the links among mitochondrial impairment, oxidative stress, autophagy, endoplasmic reticulum (ER) stress, and activation of the inflammasome still need to be clarified. In light of this deficit, we aim to provide a review of the existing literature concerning the complicated crosstalk between mitochondrial impairment, autophagy, ER stress, and the inflammasome in the molecular pathogenesis of T2D.

RalA exerts an inhibitory effect on IL-1β/IL-18 secretion by blocking NLRP3 inflammasome activation in levornidazole-treated human THP-1 macrophages

The NLRP3 inflammasome is an important mediator of inflammatory responses and its regulation is an active area of research. RalA is a Ras-like GTPase, which play pivotal roles in the biology of cells. So far, there have been very few studies on RalA regulating inflammatory responses. Bioinformatics analysis predicted that RalA might participate in the regulatory network of NLRP3 inflammasome, which has been confirmed in THP-1 macrophages. After virtual screening of compounds, it was found that levonidazole selected from our virtual small molecule compound library has the potential to bind to RalA. Of note, the interaction of RalA/levornidazole was verified by Surface Plasmon Resonance-Biacore T200, LC/MS analysis and Western blotting analysis. Molecular dynamics simulations revealed that the conformational changes of RalA might be regulated by levornidazole. Additionally, IL-1β/IL-18 secretion from ATP + LPS stimulated THP-1-derived macrophages was RalA-dependently suppressed by levornidazole, suggesting that RalA might have an inhibitory effect on NLRP3 inflammasome activation. The results of co-immunoprecipitation and RalA depletion experiments showed that levornidazole could induce RalA to block the assembly of NLRP3/ASC/pro-caspase-1 complex, thereby reducing the levels of cleaved-caspase-1 and IL-1β/IL-18 secretion. Our study has suggested an anti-inflammatory function of RalA and identified its targeting chemical compound. Overall, this study clarifies a novel pharmacological mechanism by which RalA/levornidazole inhibits NLRP3 inflammasome activation and IL-1β/IL-18 secretion.

Phosphatase-independent functions of SHP2 and its regulation by small molecule compounds

SHP2 is a non-receptor protein tyrosine phosphatase encoded by the PTPN11 gene in human. Clinically, SHP2 has been identified as a causal factor of several diseases, such as Noonan syndrome, LEOPARD syndrome as well as myeloid malignancies. Interestingly, both loss-of-function and gain-of-function mutations occur in the PTPN11 gene. Analyses by biochemical and cell biological means as well as probing with small molecule compounds have demonstrated that SHP2 has both phosphatase-dependent and independent functions. In comparison with its phosphatase activity, the non-phosphatase-like function of SHP2 has not been well introduced or summarized. This review mainly focuses on the phosphatase-independent functions and its regulation by small molecule compounds as well as their use for disease therapy.

The Role of Protein Tyrosine Phosphatases in Inflammasome Activation

Inflammasomes are multi-protein complexes that mediate the activation and secretion of the inflammatory cytokines IL-1β and IL-18. More than half a decade ago, it has been shown that the inflammasome adaptor molecule, ASC requires tyrosine phosphorylation to allow effective inflammasome assembly and sustained IL-1β/IL-18 release. This finding provided evidence that the tyrosine phosphorylation status of inflammasome components affects inflammasome assembly and that inflammasomes are subjected to regulation via kinases and phosphatases. In the subsequent years, it was reported that activation of the inflammasome receptor molecule, NLRP3, is modulated via tyrosine phosphorylation as well, and that NLRP3 de-phosphorylation at specific tyrosine residues was required for inflammasome assembly and sustained IL-1β/IL-18 release. These findings demonstrated the importance of tyrosine phosphorylation as a key modulator of inflammasome activity. Following these initial reports, additional work elucidated that the activity of several inflammasome components is dictated via their phosphorylation status. Particularly, the action of specific tyrosine kinases and phosphatases are of critical importance for the regulation of inflammasome assembly and activity. By summarizing the currently available literature on the interaction of tyrosine phosphatases with inflammasome components we here provide an overview how tyrosine phosphatases affect the activation status of inflammasomes.

Growth Factors, and Cytokines; Understanding the Role of Tyrosine Phosphatase SHP2 in Gametogenesis and Early Embryo Development

Growth factors and cytokines have vital roles in germ cell development, gamete maturation, and early embryo development. Cell surface receptors are present for growth factors and cytokines to integrate with and trigger protein signaling in the germ and embryo intracellular milieu. Src-homology-2-containing phosphotyrosine phosphatase (SHP2) is a ubiquitously expressed, multifunctional protein that plays a central role in the signaling pathways involved in growth factor receptors, cytokine receptors, integrins, and G protein-coupled receptors. Over recent decades, researchers have recapitulated the protein signaling networks that influence gamete progenitor specification as well as gamete differentiation and maturation. SHP2 plays an indispensable role in cellular growth, survival, proliferation, differentiation, and migration, as well as the basic events in gametogenesis and early embryo development. SHP2, a classic cytosolic protein and a key regulator of signal transduction, displays unconventional nuclear expression in the genital organs. Several observations provided shreds of evidence that this behavior is essential for fertility. The growth factor and cytokine-dependent roles of SHP2 and its nuclear/cytoplasmic presence during gamete maturation, early embryonic development and embryo implantation are fascinating and complex subjects. This review is intended to summarize the previous and recent knowledge about the SHP2 functions in gametogenesis and early embryo development.

Disrupting phosphatase SHP2 in macrophages protects mice from high-fat diet-induced hepatic steatosis and insulin resistance by elevating IL-18 levels

Chronic low-grade inflammation plays an important role in the pathogenesis of type 2 diabetes. Src homology 2 domain-containing tyrosine phosphatase-2 (SHP2) has been reported to play diverse roles in different tissues during the development of metabolic disorders. We previously reported that SHP2 inhibition in macrophages results in increased cytokine production. Here, we investigated the association between SHP2 inhibition in macrophages and the development of metabolic diseases. Unexpectedly, we found that mice with a conditional SHP2 knockout in macrophages (cSHP2-KO) have ameliorated metabolic disorders. cSHP2-KO mice fed a high-fat diet (HFD) gained less body weight and exhibited decreased hepatic steatosis, as well as improved glucose intolerance and insulin sensitivity, compared with HFD-fed WT littermates. Further experiments revealed that SHP2 deficiency leads to hyperactivation of caspase-1 and subsequent elevation of interleukin 18 (IL-18) levels, both in vivo and in vitro Of note, IL-18 neutralization and caspase-1 knockout reversed the amelioration of hepatic steatosis and insulin resistance observed in the cSHP2-KO mice. Administration of two specific SHP2 inhibitors, SHP099 and Phps1, improved HFD-induced hepatic steatosis and insulin resistance. Our findings provide detailed insights into the role of macrophagic SHP2 in metabolic disorders. We conclude that pharmacological inhibition of SHP2 may represent a therapeutic strategy for the management of type 2 diabetes.

Cigarette smoke extract increases mitochondrial membrane permeability through activation of adenine nucleotide translocator (ANT) in lung epithelial cells

Cigarette smoke is one of major risk factors in the pathogenesis of chronic obstructive pulmonary disease (COPD). It is generally believed that cigarette smoke induces mitochondrial damage in the alveolar epithelial cells to contribute to COPD. However, the exact molecular mechanism remains unknown for the mitochondrial damage. In this study, cigarette smoke extract (CSE) was found to induce the mitochondrial membrane permeability (MMP), which promoted proton leakage leading to the reduction in mitochondrial potential and ATP production. ANT in the mitochondrial inner membrane was activated by CSE for the alteration of MMP. The activation was observed without an alteration in the protein level of ANT. Inhibition of the ANT activity with ADP or bongkrekic acid prevented the MMP alteration and potential drop upon CSE exposure. The ANT activation was observed with a rise in ROS production, inhibition of the mitochondrial respiration, decrease in the complex III protein and rise in mitophagy activity. The results suggest that ANT may mediate the toxic effect of cigarette smoke on mitochondria and control of ANT activity is a potential strategy in intervention of the toxicity.

Inhibition of AIM2 inflammasome-mediated pyroptosis by Andrographolide contributes to amelioration of radiation-induced lung inflammation and fibrosis

Radiation-induced lung injury (RILI) is one of the most common and fatal complications of thoracic radiotherapy, whereas no effective interventions are available. Andrographolide, an active component extracted from Andrographis paniculate, is prescribed as a treatment for upper respiratory tract infection. Here we report the potential radioprotective effect and mechanism of Andrographolide on RILI. C57BL/6 mice were exposed to 18 Gy of whole thorax irradiation, followed by intraperitoneal injection of Andrographolide every other day for 4 weeks. Andrographolide significantly ameliorated radiation-induced lung tissue damage, inflammatory cell infiltration, and pro-inflammatory cytokine release in the early phase and progressive fibrosis in the late phase. Moreover, Andrographolide markedly hampered radiation-induced activation of the AIM2 inflammasome and pyroptosis in vivo. Furthermore, bone marrow-derived macrophages (BMDMs) were exposed to 8 Gy of X-ray radiation in vitro and Andrographolide significantly inhibited AIM2 inflammasome mediated-pyroptosis in BMDMs. Mechanistically, Andrographolide effectively prevented AIM2 from translocating into the nucleus to sense DNA damage induced by radiation or chemotherapeutic agents in BMDMs. Taken together, Andrographolide ameliorates RILI by suppressing AIM2 inflammasome mediated-pyroptosis in macrophage, identifying Andrographolide as a novel potential protective agent for RILI.

Targeting SHP2 as a promising strategy for cancer immunotherapy

Src homology-2-containing protein tyrosine phosphatase 2 (SHP2) is a major phosphatase involved in several cellular processes. In recent years, SHP2 has been the focus of significant attention in human diseases, particular in cancer. Several studies have shown that SHP2 plays an important role in regulating immune cell functions in tumor microenvironment. A few clinical trials conducted using SHP2 allosteric inhibitors have shown remarkable anti-tumor benefits and good safety profiles. This review focuses on the current understanding of the regulation of SHP2 and highlights the vital roles of SHP2 in T lymphocytes, macrophages and cancer cells. It also summarizes the current development of SHP2 inhibitors as a promising strategy for cancer immunotherapy.

A new research hot spot: The role of NLRP3 inflammasome activation, a key step in pyroptosis, in diabetes and diabetic complications

Pyroptosis is a form of cell death mediated by gasdermin D (GSDMD); it is characterised by NLRP3 inflammasome activation, caspase activation, cell membrane pore formation, and the release of interleukin-1β and interleukin-18. NLRP3 inflammasome activation plays a central role in pyroptosis. Recent research has suggested that NLRP3 inflammasome activation may be involved in the occurrence and development of diabetes mellitus and its associated complications. This finding provided the impetus for us to clarify the significance of pyroptosis in diabetes. In this review, we summarise the current understanding of the molecular mechanisms involved in pyroptosis, as well as recent advances in the role of NLRP3 inflammasome activation and pyroptosis in the development of diabetes and diabetic complications.

SHP2 deficiency promotes Staphylococcus aureus pneumonia following influenza infection

Objectives

Secondary bacterial pneumonia is common following influenza infection. However, it remains unclear about the underlying molecular mechanisms.

Materials and methods

We established a mouse model of post‐influenza S aureus pneumonia using conditional Shp2 knockout mice (LysM^Cre/+:Shp2^flox/flox). The survival, bacterial clearance, pulmonary histology, phenotype of macrophages, and expression of type I interferons and chemokines were assessed between SHP2 deletion and control mice (Shp2^flox/flox). We infused additional KC and MIP‐2 to examine the reconstitution of antibacterial immune response in LysM^Cre/+:Shp2^flox/flox mice. The effect of SHP2 on signal molecules including MAPKs (JNK, p38 and Erk1/2), NF‐κB p65 and IRF3 was further detected.

Results

LysM^Cre/+:Shp2^flox/flox mice displayed impaired antibacterial immunity and high mortality compared with control mice in post‐influenza S aureus pneumonia. The attenuated antibacterial ability was associated with the induction of type I interferon and suppression of chemo‐attractants KC and MIP‐2, which reduced the infiltration of neutrophils into the lung upon secondary bacterial invasion. In additional, Shp2 knockout mice displayed enhanced polarization to alternatively activated macrophages (M2 phenotype). Further in vitro analyses consistently demonstrated that SHP2‐deficient macrophages were skewed towards an M2 phenotype and had a decreased antibacterial capacity. Moreover, SHP2 modulated the inflammatory response to secondary bacterial infection via interfering with NF‐κB and IRF3 signalling in macrophages.

Conclusions

Our findings reveal that the SHP2 expression enhances the host immune response and prompts bacterial clearance in post‐influenza S aureus pneumonia.

Tumor-associated macrophages (TAMs) depend on Shp2 for their anti-tumor roles in colorectal cancer

Tumor associated macrophages (TAMs) in tumor microenvironment can interact with tumor cells and are related to tumor progression. However, the mechanisms that drive the anti-tumor functions of TAMs are not fully understood. The Src homology 2 domain-containing tyrosine phosphatase 2 (Shp2) has been reported to have tumor-suppressing roles in colorectal cancer (CRC). However, a role for Shp2 on TAMs in CRC has not been studied. Here we report that in CRC, Shp2 expression on TAMs is negatively associated with liver metastasis. TAMs require Shp2 for their anti-tumor functions in a cell-cell co-culture system and a mouse model of CRC. Mechanistically, absence of Shp2 on TAMs induces their polarization toward M2 phenotype through the activation of p-STAT3 and inhibition of p-NF-κB p65. The findings of our study imply that Shp2 is a key factor in the tumor microenvironment to facilitate the TAMs' tumor-suppressing functions in colorectal cancer.

The pore-forming subunit Kir6.1 of the K-ATP channel negatively regulates the NLRP3 inflammasome to control insulin resistance by interacting with NLRP3

Excessive activation of the NLRP3 inflammasome is a key component contributing to the pathogenesis of various inflammatory diseases. However, the molecular mechanisms underlying its activation and regulation remain poorly defined. The objective of this study was to explore the possible function of the K⁺ channel pore-forming subunit Kir6.1 in regulating NLRP3 inflammasome activation and insulin resistance. Here, we demonstrate that Kir6.1 depletion markedly activates the NLRP3 inflammasome, whereas enhanced Kir6.1 expression produces opposing effects both in mice in vivo and in primary cells in vitro. We also demonstrate that Kir6.1 controls insulin resistance by inhibiting NLRP3 inflammasome activation in mice. We further show that Kir6.1 physically associates with NLRP3 and thus inhibits the interactions between the NLRP3 inflammasome subunits. Our results reveal a previously unrecognized function of Kir6.1 as a negative regulator of the NLRP3 inflammasome and insulin resistance, which is mediated by virtue of its ability to inhibit NLRP3 inflammasome assembly. These data provide novel insights into the regulatory mechanism of NLRP3 inflammasome activation and suggest that Kir6.1 is a promising therapeutic target for inflammasome-mediated inflammatory diseases.

Suhuang antitussive capsule inhibits NLRP3 inflammasome activation and ameliorates pulmonary dysfunction via suppression of endoplasmic reticulum stress in cough variant asthma

Pulmonary dysfunction is tightly associated with cough variant asthma (CVA), a respiratory damage disease. Suhuang antitussive capsule (Suhuang), one of traditional Chinese patent medicines, plays a crucial role in the treatment and complication of CVA in the long clinical application. In this study, we aimed to investigate the protective effects and underlying antitussive mechanisms of Suhuang on pulmonary function in ovalbumin (OVA)-induced CVA rats. Administration (i.g.) of Suhuang significantly alleviated pulmonary damage and dysfunction. Suhuang improved ER stress and PKCε translocation via regulation of Ca²⁺ trafficking. Suhuang also inhibited NLRP3 inflammasome activation, as evidenced by disrupting the assembly of NLRP3 inflammasome and reducing the expression of cleaved caspase-1, and decreased IL-1β secretion. Besides, it's identified that TXNIP induction and RIP1-RIP3-Drp1 pathway were required for the inhibitory routes of Suhuang from ER stress to NLRP3 inflammasome activation. Consistent with the in vivo findings, Suhuang also attenuated ER stress/NLRP3 inflammasome activation, and thereby restored pulmonary homeostasis in vitro. Meantime, these functions were diminished by blocking ER stress, indicating that ER stress is essential for the effects of Suhuang on pulmonary function. A further in vivo analysis showed that Suhuang-driven pharmacological inactivation of NLRP3 inflammasome and amelioration of pulmonary dysfunction were reversed by an ER stress inducer tunicamycin, well confirming the beneficial effects of Suhuang on pulmonary function by regulation of ER stress. Collectively, these results indicated that Suhuang contributed to impairing NLRP3 inflammasome activation via inhibition of ER stress, which was responsible for the protection of pulmonary homeostasis. These findings may provide a pharmacological groundwork and important new experimental data regarding the clinical treatment of Suhuang in CVA patients.

Inhibition of NLRP3 inflammasome-mediated pyroptosis in macrophage by cycloastragenol contributes to amelioration of imiquimod-induced psoriasis-like skin inflammation in mice

Psoriasis is a common chronic inflammatory skin disease, and the infiltrated macrophages in psoriatic skin lesions play a key role in the progression of this uncontrolled cutaneous inflammation. However, the current therapeutic strategies for patients with psoriasis are not satisfactory. Here, we report that cycloastragenol (CAG), a natural active small compound isolated from Astragalus membranaceus, significantly ameliorated imiquimod (IMQ)-induced psoriasiform dermatitis in mice by targeting proinflammatory macrophages. CAG significantly reduced the clinical scores, decreased the epidermal thickness, and ameliorated the deteriorating histopathology observed in IMQ-induced mice. CAG treatment specifically reduced the dermal infiltration of macrophages, rather than of dendritic cells, neutrophils, or T lymphocytes, into psoriatic skin. CAG dose-dependently decreased the level of proinflammatory cytokines, including IL-1β, TNF-α and IL-6, in murine psoriatic skin and serum, as well as in IMQ-stimulated, bone-marrow-derived macrophages. When compared to the control group, CAG significantly decreased IMQ-triggered NLRP3 inflammasome activation and gasdermin D-mediated cell pyroptosis in these proinflammatory macrophages. CAG also suppressed the assembly of the NLRP3 inflammasome complex. Taken together, the results show that CAG selectively modulates macrophage function by inhibiting NLRP3 inflammasome-mediated pyroptosis to ameliorate IMQ-induced psoriasis-like skin inflammation in mice. Our findings also identify an effective drug candidate for the treatment of psoriasis.

Treatment with 3,4-dihydroxyphenylethyl alcohol glycoside ameliorates sepsis-induced ALI in mice by reducing inflammation and regulating M1 polarization

The bioactive phenylethanoid 3,4-dihydroxyphenylethyl alcohol glycoside (DAG) is a component isolated from Sargentodoxa cuneata. The effects of DAG on acute lung injury (ALI) are largely unknown. Here, the effects of DAG on sepsis-induced ALI were investigated, and the related mechanisms were explored. Male C57BL/6 mice were used to establish a sepsis-induced ALI model. Levels of inflammatory cytokines were determined using real-time quantitative reverse transcription PCRs (qRT-PCR) and enzyme-linked immunosorbent assays (ELISAs). Pathological changes in the lung tissues were evaluated using haematoxylin and eosin (HE) staining. Mouse survival was quantified, and macrophage polarization was analyzed using flow cytometry. Our results showed that, in septic mice, pretreatment with DAG significantly improved survival, reduced histological damage in the lung, and suppressed the inflammatory response by inhibiting the activation of the NF-κB, STAT3, and p38 MAPK signaling pathways. Moreover, DAG treatment reduced the percentage of M1 macrophages in the bronchoalveolar lavage fluid (BALF) and spleen. In addition, DAG treatment decreased the production of pro-inflammatory cytokines and suppressed the activation of the NF-κB, STAT3, and p38 MAPK signaling pathways in LPS-induced MH-S cells. DAG treatment also reduced the relative abundances of M1 macrophages and M1 macrophage markers by suppressing the activation of the Notch1 signaling pathway. Thus, our results provided new insights for the development of drugs to treat ALI.

CARD9 prevents lung cancer development by suppressing the expansion of myeloid-derived suppressor cells and IDO production

Caspase recruitment domain-containing protein 9 (CARD9) is an adaptor protein and highly expressed in myeloid cells. Our previous study demonstrates a critical protective effect of CARD9 in the development of colitis-associated colon cancer. Nevertheless, the effect of CARD9 in lung cancer remains unclear. Here, using a mouse Lewis lung cancer model, we found the tumor burden of CARD9^-/- mice was much heavier than that in wild-type (WT) mice. More myeloid-derived suppressor cells (MDSCs) were accumulated and less cytotoxicity T lymphocyte was found in tumor tissues of CARD9^-/- mice, compared to WT mice. Depleting MDSCs using anti-Gr1 antibody can significantly decrease tumor burden in CARD9^-/- mice. Furthermore, the noncanonical nuclear factor-kappaB (NF-κB) pathway was activated in CARD9^-/- mice-derived MDSCs. Deficiency of CARD9 enhanced expression of indoleamine 2,3-dioxygenase (IDO) in MDSCs via noncanonical NF-κB pathway. Moreover, correlations between CARD9 expressions and MDSCs relative genes (IDO, iNOS-2 and arginase 1 [ARG-1]) were further confirmed in tumor tissues from lung cancer patients. Taken together, we showed a CARD9-NF-κB-IDO pathway in MDSCs which can inhibit the suppressive function of MDSCs and prevent lung cancer development.

Evodiamine Augments NLRP3 Inflammasome Activation and Anti-bacterial Responses Through Inducing α-Tubulin Acetylation

Evodiamine is a major ingredient of the plant Evodia rutaecarpa, which has long been used for treating infection-related diseases including diarrhea, beriberi and oral ulcer, but the underlying mechanism is unclear. Here we aimed to explore whether evodiamine influenced NLRP3 (NLR family, pyrin containing domain 3) inflammasome activation in macrophages, which is a critical mechanism for defending the host against pathogenic infections. We uncovered that evodiamine dose-dependently enhanced NLRP3 inflammasome activation in lipopolysaccharide-primed macrophages, as indicated by increased interleukin (IL)-1β production and caspase-1 cleavage, accompanied by increased ASC speck formation and pyroptosis. Mechanistically, evodiamine induced acetylation of α-tubulin around the microtubule organization center (indicated by γ-tubulin) in lipopolysaccharide-primed macrophages. Such evodiamine-mediated increases in NLRP3 activation and pyroptosis were attenuated by activators of α-tubulin deacetylase, resveratrol and NAD⁺, or dynein-specific inhibitor ciliobrevin A. Small interfering RNA knockdown of αTAT1 (the gene encoding α-tubulin N-acetyltransferase) expression, which reduced α-tubulin acetylation, also diminished evodiamine-mediated augmentation of NLRP3 activation and pyroptosis. Evodiamine also enhanced NLRP3-mediated production of IL-1β and neutrophil recruitment in vivo. Moreover, evodiamine administration evidently improved survival of mice with lethal bacterial infection, accompanied by increased production of IL-1β and interferon-γ, decreased bacterial load, and dampened liver inflammation. Resveratrol treatment reversed evodiamine-induced increases of IL-1β and interferon-γ, and decreased bacterial clearance in mice. Collectively, our results indicated that evodiamine augmented the NLRP3 inflammasome activation through inducing α-tubulin acetylation, thereby conferring intensified innate immunity against bacterial infection.

MALAT1 Up-Regulator Polydatin Protects Brain Microvascular Integrity and Ameliorates Stroke Through C/EBPβ/MALAT1/CREB/PGC-1α/PPARγ Pathway

Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is a long non-coding RNA contributing to protect the blood-brain barrier (BBB) after stroke. We searched for small molecules that may up-regulate MALAT1 and focused on polydatin (PD), a natural product, as a possible candidate. PD enhanced MALAT1 gene expression in rat brain microvascular endothelial cells, reducing cell toxicity and apoptosis after oxygen and glucose deprivation (OGD). These effects correlated with reduction of inflammatory factors and enhancement of expression of BBB markers. We found opposite changes after MALAT1 silencing. We determined that C/EBPβ is a key transcription factor for PD-mediated MALAT1 expression. PPARγ activity is involved in MALAT1 protective effects through its coactivator PGC-1α and the transcription factor CREB. This suggests that PD activates the MALAT1/CREB/PGC-1α/PPARγ signaling pathway to protect endothelial cells against ischemia. PD administration to rats subjected to brain ischemia by transient middle cerebral artery occlusion (tMCAO) reduced cerebral infarct volume and brain inflammation, protected cerebrovascular endothelial cells and BBB integrity. These effects correlated with increased expression of MALAT1, C/EBPβ, and PGC-1α. Our results strongly suggest that the beneficial effects of PD involve the C/EBPβ/MALAT1/CREB/PGC-1α/PPARγ pathway, which may provide a novel therapeutic strategy for brain ischemic stroke.

TAT-Ngn2 Enhances Cognitive Function Recovery and Regulates Caspase-Dependent and Mitochondrial Apoptotic Pathways After Experimental Stroke

Neurogenin-2 (Ngn2) is a basic helix-loop-helix (bHLH) transcription factor that contributes to the identification and specification of neuronal fate during neurogenesis. In our previous study, we found that Ngn2 plays an important role in alleviating neuronal apoptosis, which may be viewed as an attractive candidate target for the treatment of cerebral ischemia. However, novel strategies require an understanding of the function and mechanism of Ngn2 in mature hippocampal neurons after global cerebral ischemic injury. Here, we found that the expression of Ngn2 decreased in the hippocampus after global cerebral ischemic injury in mice and in primary hippocampal neurons after oxygen glucose deprivation (OGD) injury. Then, transactivator of transcription (TAT)-Ngn2, which was constructed by fusing a TAT domain to Ngn2, was effectively transported and incorporated into hippocampal neurons after intraperitoneal (i.p.) injection and enhanced cognitive functional recovery in the acute stage after reperfusion. Furthermore, TAT-Ngn2 alleviated hippocampal neuronal damage and apoptosis, and inhibited the cytochrome C (CytC) leak from the mitochondria to the cytoplasm through regulating the expression levels of brain-derived neurotrophic factor (BDNF), phosphorylation tropomyosin-related kinase B (pTrkB), Bcl-2, Bax and cleaved caspase-3 after reperfusion injury in vivo and in vitro. These findings suggest that the downregulation of Ngn2 expression may have an important role in triggering brain injury after ischemic stroke and that the neuroprotection of TAT-Ngn2 against stroke might involve the modulation of BDNF-TrkB signaling that regulates caspase-dependent and mitochondrial apoptotic pathways, which may be an attractive therapeutic strategy for cerebral ischemic injury.

The inner mitochondrial membrane protein ANT1 modulates IL-6 expression via the JNK pathway in macrophages

Mitochondria are increasingly associated with inflammation. Here, we focus on the relationship between inflammation and adenine nucleotide translocator type 1 (ANT1), which is localized in the mitochondrial inner membrane. ANT1 plays an important role in oxidative phosphorylation, and mutations in the ANT1 gene are responsible for mitochondrial diseases. Ample studies have demonstrated that ANT1 has a critical role in cardiomyocytes and neurons, but little has been reported on its functions in immune cells. We knocked down ANT1 expression in macrophages and examined inflammatory cytokine expression after lipopolysaccharide stimulation. ANT1 knockdown reduces the expression of IL-6. JNK, upstream of IL-6, is downregulated, but other MAP kinases and the NF-κB signaling remain unchanged. These results suggest that ANT1 modulates IL-6 expression through JNK in macrophages.

Smiglaside A ameliorates LPS-induced acute lung injury by modulating macrophage polarization via AMPK-PPARγ pathway

Macrophages, which have various phenotypes and diverse functions, are becoming the target cells in inflammatory diseases. In this study, we evaluated the effects of the natural product smiglaside A, a phenylpropanoid glycoside isolated from the traditional Chinese medicinal herb Smilax riparia, on macrophage polarization and investigated the underlying mechanisms. We found that smiglaside A promoted M2 polarization and reduced M1 polarization in LPS-stimulated RAW264.7 cells and primary mouse peritoneal macrophages. Further mechanistic studies showed that the promoting effect of smiglaside A on M2 polarization was attenuated by pharmacological inhibition or gene silencing of AMP-activated protein kinase (AMPK) or peroxisome proliferator-activated receptor γ (PPARγ). Moreover, smiglaside A-enhanced PPARγ activity was prevented by the AMPK inhibitor compound C and by an siRNA. These findings indicate that the AMPK-PPARγ pathway is involved in promotion of M2 macrophages by smiglaside A. In a mouse model of LPS-induced acute lung injury, smiglaside A significantly increased the survival rate of LPS-injected mice and ameliorated the LPS-induced inflammatory response and lung damage. In addition, smiglaside A enhanced the protein expression levels of phosphorylated AMPK and PPARγ in the lung and promoted alveolar macrophages to the M2 phenotype in this mouse model. Taken together, our results indicate that smiglaside A can promote macrophage polarization to an anti-inflammatory M2 phenotype via stimulating the AMPK-PPARγ signaling pathway. Our study may provide novel approaches and/or targets for drug development to treat inflammatory diseases such as acute lung injury and sepsis.

RAS signalling in energy metabolism and rare human diseases

The RAS pathway is a highly conserved cascade of protein-protein interactions and phosphorylation that is at the heart of signalling networks that govern proliferation, differentiation and cell survival. Recent findings indicate that the RAS pathway plays a role in the regulation of energy metabolism via the control of mitochondrial form and function but little is known on the participation of this effect in RAS-related rare human genetic diseases. Germline mutations that hyperactivate the RAS pathway have been discovered and linked to human developmental disorders that are known as RASopathies. Individuals with RASopathies, which are estimated to affect approximately 1/1000 human birth, share many overlapping characteristics, including cardiac malformations, short stature, neurocognitive impairment, craniofacial dysmorphy, cutaneous, musculoskeletal, and ocular abnormalities, hypotonia and a predisposition to developing cancer. Since the identification of the first RASopathy, type 1 neurofibromatosis (NF1), which is caused by the inactivation of neurofibromin 1, several other syndromes have been associated with mutations in the core components of the RAS-MAPK pathway. These syndromes include Noonan syndrome (NS), Noonan syndrome with multiple lentigines (NSML), which was formerly called LEOPARD syndrome, Costello syndrome (CS), cardio-facio-cutaneous syndrome (CFC), Legius syndrome (LS) and capillary malformation-arteriovenous malformation syndrome (CM-AVM). Here, we review current knowledge about the bioenergetics of the RASopathies and discuss the molecular control of energy homeostasis and mitochondrial physiology by the RAS pathway.