RIPK1 dephosphorylation and kinase activation by PPP1R3G/PP1γ promote apoptosis and necroptosis

Comprehensive pan-cancer analysis of PPP1R3G reveals its diagnostic, prognostic, and immunotherapeutic implications

BACKGROUND

PPP1R3G, a regulatory subunit of protein phosphatase 1, plays a critical role in glycogen metabolism and has been implicated in various cancers. This study provides a comprehensive pan-cancer analysis of PPP1R3G, evaluating its expression, diagnostic and prognostic significance, and potential as a therapeutic target.

METHODS

We performed an extensive pan-cancer analysis of PPP1R3G using several databases to assess its expression and investigate its correlations with clinical outcomes. Our investigation included assessing PPP1R3G's impact on survival, its correlation with immune checkpoints and tumor stemness scores, and its prognostic significance. We also explored its relationship with immunomodulators, genomic profiles, and immunological characteristics, as well as its response to immunotherapy and involvement in various biological pathways.

RESULTS

PPP1R3G expression varied significantly across different cancers and correlated with both diagnostic and prognostic outcomes. Moreover, PPP1R3G was significantly linked to immune checkpoints, immunomodulators, prognosis, immunoregulatory genes, tumor stemness, cellular function, and immune infiltration across numerous cancer types. Further analysis of PPP1R3G-related gene enrichment, mutation profiles, RNA modifications, and genomic heterogeneity revealed that missense mutations were the predominant alteration affecting PPP1R3G.

CONCLUSIONS

Overall, the expression of PPP1R3G is closely associated with various cancers and may serve as a potential biomarker for cancer detection.

The Role of Post-Translational Modifications in Necroptosis

Necroptosis, a distinct form of regulated necrosis implicated in various human pathologies, is orchestrated through sophisticated signaling pathways. During this process, cells undergoing necroptosis exhibit characteristic necrotic morphology and provoke substantial inflammatory responses. Post-translational modifications (PTMs)-chemical alterations occurring after protein synthesis that critically regulate protein functionality-constitute essential regulatory components within these complex signaling cascades. This intricate crosstalk between necroptotic pathways and PTM networks presents promising therapeutic opportunities. Our comprehensive review systematically analyzes the molecular mechanisms underlying necroptosis, with particular emphasis on the regulatory roles of PTMs in signal transduction. Through systematic evaluation of key modifications including ubiquitination, phosphorylation, glycosylation, methylation, acetylation, disulfide bond formation, caspase cleavage, nitrosylation, and SUMOylation, we examine potential therapeutic applications targeting necroptosis in disease pathogenesis. Furthermore, we synthesize current pharmacological strategies for manipulating PTM-regulated necroptosis, offering novel perspectives on clinical target development and therapeutic intervention.

Cathepsin B induces kidney diseases through different types of programmed cell death

Cathepsin B (CTSB), a key cysteine protease, plays essential roles in physiological and pathological processes. As research progresses, interest in how CTSB triggers different types of programmed cell death (PCD) to induce the onset and development of diseases is increasing. Several recent studies suggest that different types of PCD mediated by CTSB play key roles in kidney diseases. In this review, we outline the fundamental mechanisms by which CTSB triggers different types of PCD in several kidney diseases and discuss the function of CTSB in various segments of the kidney. Moreover, we explore the possibilities and prospects of using CTSB as a therapeutic target for kidney diseases.

New insights into pulmonary arterial hypertension: interaction between PANoptosis and perivascular inflammatory responses

Pulmonary arterial hypertension (PAH) is a heterogeneous disease characterized by various etiologies, with pulmonary vascular remodeling recognized as a main pathological change. Currently, it is widely accepted that vascular remodeling is closely associated with abnormal pulmonary vascular cell death and perivascular inflammation. The simultaneous activation of various pulmonary vascular cell death leads to immune cell adhesion and inflammatory mediator releases; And in turn, the inflammatory response may also trigger cell death and jointly promote the progression of vascular remodeling. Recently, PANoptosis has been identified as a phenomenon that describes the simultaneous activation and interaction of multiple forms of programmed cell death (PCD). Therefore, the relationship between PANoptosis and inflammation in PAH warrants further investigation. This review examines the mechanisms underlying apoptosis, necroptosis, pyroptosis, and inflammatory responses in PAH, with a focus on PANoptosis and its interactions with inflammation. And it aims to elucidate the significance of this emerging form of cell death and inflammation in the pathophysiology of PAH and to explore its potential as a therapeutic target.

RIPK1 in necroptosis and recent progress in related pharmaceutics

Necroptosis is a programmed form of cell death. Receptor-interacting serine/threonine protein kinase l (RIPK1) is a crucial protein kinase that regulates the necroptosis pathway. Increased expression of death receptor family ligands such as tumor necrosis factor (TNF) increases the susceptibility of cells to apoptosis and necroptosis. RIPK1, RIPK3, and mixed-lineage kinase-like domain (MLKL) proteins mediate necrosis. RIPK1-mediated necroptosis further promotes cell death and inflammation in the pathogenesis of liver injury, skin diseases, and neurodegenerative diseases. The N-terminal kinase domain of RIPK1 is significant in the induction of cell death and can be used as a vital drug target for inhibitors. In this paper, we outline the pathways of necroptosis and the role RIPK1 plays in them and suggest that targeting RIPK1 in therapy may help to inhibit multiple cell death pathways.

Prognostic significance of elevated expression levels of protein phosphatase 1 regulatory subunit 3G in thyroid carcinoma

The prognosis of the poorly differentiated subtype of thyroid carcinoma (THCA) is less favorable due to its aggressive nature, which also increases the likelihood of metastasis to distant organs. The present study aimed to assess the potential application of protein phosphatase 1 regulatory subunit 3G (PPP1R3G) as a molecular biomarker for early identification and prognosis prediction in THCA. The Cancer Genome Atlas (TCGA) database was used to identify genes associated with prognosis and differentially expressed genes in THCA. Additionally, TCGA data were used to analyze the differential expression of the PPP1R3G gene in THCA tissues compared with that in normal tissues. Immunohistochemistry was used for further confirmation of these findings. A prognostic significance analysis of the PPP1R3G gene was performed in patients diagnosed with THCA using Cox regression models. Both univariate and multivariate approaches were used, incorporating clinical information obtained from the patients. Moreover, to gain insights into the molecular mechanisms underlying the regulatory role of the PPP1R3G gene in THCA, a functional enrichment analysis performed. An assessment of the levels of immune cell infiltration in patients with THCA was also performed and their correlation with the expression level of PPP1R3G gene was assessed. The mRNA and protein levels of PPP1R3G were revealed to be higher in THCA tissues compared with that of noncancerous thyroid tissues. Moreover, there were significant associations between the expression of PPP1R3G in THCA and factors such as sex, histological type, pathological node stage, pathological stage, extrathyroidal extension and overall survival (OS). Univariate and multivariate Cox regression analyses revealed that the independent prognostic value of PPP1R3G could be used to predict the OS of patients with THCA. The outcomes obtained from functional enrichment analysis indicated a potential involvement of PPP1R3G in regulation of biological processes such as keratinization, and differentiation of keratinocytes and epidermal cells. Additionally, an association was demonstrated between the expression levels of PPP1R3G gene and several immune cells present within the tumor microenvironment of the thyroid. In conclusion, PPP1R3G has the potential to serve as a prognostic indicator for patients diagnosed with THCA, and may also be considered a promising target for therapeutic interventions in THCA.

SHP2-Triggered Endothelial Cell Activation Fuels Estradiol-Independent Endometrial Sterile Inflammation

Sterile inflammation occurs in various chronic diseases due to many nonmicrobe factors. Examples include endometrial hyperplasia (EH), endometriosis, endometrial cancer, and breast cancer, which are all sterile inflammation diseases induced by estrogen imbalances. However, how estrogen-induced sterile inflammation regulates EH remains unclear. Here, a single-cell RNA-Seq is used to show that SHP2 upregulation in endometrial endothelial cells promotes their inflammatory activation and subsequent transendothelial macrophage migration. Independent of the initial estrogen stimulation, IL1β and TNFα from macrophages then create a feedforward loop that enhances endothelial cell activation and IGF1 secretion. This endothelial cell-macrophage interaction sustains sterile endometrial inflammation and facilitates epithelial cell proliferation, even after estradiol withdrawal. The bulk RNA-Seq results and phosphoproteomic analysis show that endothelial SHP2 mechanistically enhances RIPK1 activity by dephosphorylating RIPK1Tyr380. This event activates downstream activator protein 1 (AP-1) and instigates the inflammation response. Furthermore, targeting SHP2 using SHP099 (an allosteric inhibitor) or endothelial-specific SHP2 deletion alleviates endothelial cell activation, macrophage infiltration, and EH progression in mice. Collectively, the findings demonstrate that SHP2 mediates the transition of endothelial activation from estradiol-driven acute inflammation to macrophage-amplified chronic inflammation. Targeting sterile inflammation mediated by endothelial cell activation is a promising strategy for nonhormonal intervention in estrogen-related diseases.

Receptor-interacting protein kinase 1 confers autophagic promotion of gasdermin E-mediated pyroptosis in aristolochic acid-induced acute kidney injury

Aristolochic acid (AA) exposure is a severe public health concern worldwide. AAs damage the kidney with an inevitable acute phase that is similar to acute kidney injury (AKI). Gasdermin E (GSDME) is abundant in the kidney; thus; it-mediated pyroptosis might be essential in connecting cell death and inflammation and promoting AAs-AKI. However, the role and exact mechanism of pyroptosis in AAs-AKI have not been investigated. In this study, aristolochic acid I (AAI) was used to establish AKI models. The expression and translocation results showed GSDME-mediated pyroptosis in AAI-AKI. Knocking down GSDME attenuated AAI-induced cell death and transcription of proinflammatory cytokines. Mechanistic research inhibiting caspase (casp) 3, casp 8, and casp 9 with specific chemical antagonists demonstrated that GSDME was activated by cleaved casp 3. Furthermore, the kinase activity of upstream receptor-interacting protein kinase 1 (RIPK1) was significantly elevated, and inhibiting RIPK1 with specific inhibitors markedly improved AAI-induced cell damage. In addition, the level of autophagy was obviously increased. Pretreatment with a specific autophagic inhibitor (3-methyladenine) or knockdown of autophagic genes (Atg5 or Atg7) evidently reduced the activity of RIPK1 and downstream apoptosis and pyroptosis, thus attenuating AA-induced cell injury, which suggested that RIPK1 was a novel link conferring autophagic promotion of pyroptosis. These findings reveal GSDME-mediated pyroptosis for the first time in AAI-induced AKI, propose its novel role in the transcription of cytokines, and demonstrate that autophagy promotes pyroptosis via the RIPK1-dependent apoptotic pathway. This study promotes the understanding of the toxic effects and exact mechanisms of AAs. This will contribute to evaluating the environmental risk of AA exposure and might provide potential therapeutic targets for AA-AKI.

Let's make it personal: CRISPR tools in manipulating cell death pathways for cancer treatment

Advancements in the CRISPR technology, a game-changer in experimental research, have revolutionized various fields of life sciences and more profoundly, cancer research. Cell death pathways are among the most deregulated in cancer cells and are considered as critical aspects in cancer development. Through decades, our knowledge of the mechanisms orchestrating programmed cellular death has increased substantially, attributed to the revolution of cutting-edge technologies. The heroic appearance of CRISPR systems have expanded the available screening platform and genome engineering toolbox to detect mutations and create precise genome edits. In that context, the precise ability of this system for identification and targeting of mutations in cell death signaling pathways that result in cancer development and therapy resistance is an auspicious choice to transform and accelerate the individualized cancer therapy. The concept of personalized cancer therapy stands on the identification of molecular characterization of the individual tumor and its microenvironment in order to provide a precise treatment with the highest possible outcome and minimum toxicity. This study explored the potential of CRISPR technology in precision cancer treatment by identifying and targeting specific cell death pathways. It showed the promise of CRISPR in finding key components and mutations involved in programmed cell death, making it a potential tool for targeted cancer therapy. However, this study also highlighted the challenges and limitations that need to be addressed in future research to fully realize the potential of CRISPR in cancer treatment.

Regulation of RIPK1 Phosphorylation: Implications for Inflammation, Cell Death, and Therapeutic Interventions

Receptor-interacting protein kinase 1 (RIPK1) plays a crucial role in controlling inflammation and cell death. Its function is tightly controlled through post-translational modifications, enabling its dynamic switch between promoting cell survival and triggering cell death. Phosphorylation of RIPK1 at various sites serves as a critical mechanism for regulating its activity, exerting either activating or inhibitory effects. Perturbations in RIPK1 phosphorylation status have profound implications for the development of severe inflammatory diseases in humans. This review explores the intricate regulation of RIPK1 phosphorylation and dephosphorylation and highlights the potential of targeting RIPK1 phosphorylation as a promising therapeutic strategy for mitigating human diseases.

The protein phosphatase PP6 promotes RIPK1-dependent PANoptosis

BACKGROUND

The innate immune system serves as the first line of host defense. Transforming growth factor-β-activated kinase 1 (TAK1) is a key regulator of innate immunity, cell survival, and cellular homeostasis. Because of its importance in immunity, several pathogens have evolved to carry TAK1 inhibitors. In response, hosts have evolved to sense TAK1 inhibition and induce robust lytic cell death, PANoptosis, mediated by the RIPK1-PANoptosome. PANoptosis is a unique innate immune inflammatory lytic cell death pathway initiated by an innate immune sensor and driven by caspases and RIPKs. While PANoptosis can be beneficial to clear pathogens, excess activation is linked to pathology. Therefore, understanding the molecular mechanisms regulating TAK1 inhibitor (TAK1i)-induced PANoptosis is central to our understanding of RIPK1 in health and disease.

RESULTS

In this study, by analyzing results from a cell death-based CRISPR screen, we identified protein phosphatase 6 (PP6) holoenzyme components as regulators of TAK1i-induced PANoptosis. Loss of the PP6 enzymatic component, PPP6C, significantly reduced TAK1i-induced PANoptosis. Additionally, the PP6 regulatory subunits PPP6R1, PPP6R2, and PPP6R3 had redundant roles in regulating TAK1i-induced PANoptosis, and their combined depletion was required to block TAK1i-induced cell death. Mechanistically, PPP6C and its regulatory subunits promoted the pro-death S166 auto-phosphorylation of RIPK1 and led to a reduction in the pro-survival S321 phosphorylation.

CONCLUSIONS

Overall, our findings demonstrate a key requirement for the phosphatase PP6 complex in the activation of TAK1i-induced, RIPK1-dependent PANoptosis, suggesting this complex could be therapeutically targeted in inflammatory conditions.

Protein phosphorylation and kinases: Potential therapeutic targets in necroptosis

Necroptosis is a pivotal contributor to the pathogenesis of various human diseases, including those affecting the nervous system, cardiovascular system, pulmonary system, and kidneys. Extensive investigations have elucidated the mechanisms and physiological ramifications of necroptosis. Among these, protein phosphorylation emerges as a paramount regulatory process, facilitating the activation or inhibition of specific proteins through the addition of phosphate groups to their corresponding amino acid residues. Currently, the targeting of kinases has gained recognition as a firmly established and efficacious therapeutic approach for diverse diseases, notably cancer. In this comprehensive review, we elucidate the intricate role of phosphorylation in governing key molecular players in the necroptotic pathway. Moreover, we provide an in-depth analysis of recent advancements in the development of kinase inhibitors aimed at modulating necroptosis. Lastly, we deliberate on the prospects and challenges associated with the utilization of kinase inhibitors to modulate necroptotic processes.

5-HT-treated mouse B cells alleviate ulcerative colitis via RIPK1: Insights from proteomic and phosphoproteomic analyses

5-hydroxytryptamine (5-HT) exerts various physiological effects on the intestine through different signaling pathways and molecular transmission mechanisms, including pro- and anti-inflammatory effects. Adoptive transfer of regulatory B cells (Bregs) into colitis mice has exhibited significant therapeutic benefits. We aimed to elucidate the mechanism through which 5-HT-treated B cells alleviate ulcerative colitis. To this end, we analyzed the proteomic and phosphoproteomic profiles of 5-HT-stimulated B cells from naïve mice. We identified 3124 phosphorylation sites in proteins via tandem mass tagging and found 110 differential peptides after protein phosphorylation. Furthermore, we obtained three differential proteins, RIPK1, ATXN2l, and Q8C5K5 through integration of both proteomic datasets. We discovered and validated that 5-HT binds to 5-HT7R and increases the expression of RIPK1 in B cells. We propose a theoretical and experimental basis for further research on the RIPK1 signaling pathway, kinase prediction, and phosphorylation sites in ulcerative colitis. SIGNIFICANCE: Some researchers demonstrated that 5-HT can effectively suppress colitis through a variety of molecular mechanisms. Our study discovered and consistently validated the 5-HT/5-HT7R/RIPK1 pathway, further clarifying the molecular mechanism through which 5-HT stimulates B cells to alleviate intestinal inflammation.

A strategy to disentangle direct and indirect effects on (de)phosphorylation by chemical modulators of the phosphatase PP1 in complex cellular contexts

Chemical activators and inhibitors are useful probes to identify substrates and downstream effects of enzymes; however, due to the complex signaling environment within cells, it is challenging to distinguish between direct and indirect effects. This is particularly the case for phosphorylation, where a single (de)phosphorylation event can trigger rapid changes in many other phosphorylation sites. An additional complication arises when a single catalytic entity, which acts in the form of many different holoenzymes with different substrates, is activated or inhibited, as it is unclear which holoenzymes are affected, and in turn which of their substrates are (de)phosphorylated. Direct target engaging MS-based technologies to study targets of drugs do not address these challenges. Here, we tackle this by studying the modulation of protein phosphatase-1 (PP1) activity by PP1-disrupting peptides (PDPs), as well as their selectivity toward PP1, by using a combination of mass spectrometry-based experiments. By combining cellular treatment with the PDP with in vitro dephosphorylation by the enzyme, we identify high confidence substrate candidates and begin to separate direct and indirect effects. Together with experiments analyzing which holoenzymes are particularly susceptible to this treatment, we obtain insights into the effect of the modulator on the complex network of protein (de)phosphorylation. This strategy holds promise for enhancing our understanding of PP1 in particular and, due to the broad applicability of the workflow and the MS-based read-out, of chemical modulators with complex mode of action in general.

MLKL polymerization-induced lysosomal membrane permeabilization promotes necroptosis

Mixed lineage kinase-like protein (MLKL) forms amyloid-like polymers to promote necroptosis; however, the mechanism through which these polymers trigger cell death is not clear. We have determined that activated MLKL translocates to the lysosomal membrane during necroptosis induction. The subsequent polymerization of MLKL induces lysosome clustering and fusion and eventual lysosomal membrane permeabilization (LMP). This LMP leads to the rapid release of lysosomal contents into the cytosol, resulting in a massive surge in cathepsin levels, with Cathepsin B (CTSB) as a significant contributor to the ensuing cell death as it cleaves many proteins essential for cell survival. Importantly, chemical inhibition or knockdown of CTSB protects cells from necroptosis. Furthermore, induced polymerization of the MLKL N-terminal domain (NTD) also triggers LMP, leading to CTSB release and subsequent cell death. These findings clearly establish the critical role of MLKL polymerization induced lysosomal membrane permeabilization (MPI-LMP) in the process of necroptosis.

Decreased PPP1R3G in pre-eclampsia impairs human trophoblast invasion and migration via Akt/MMP-9 signaling pathway

Pre-eclampsia (PE) is a severe pregnancy complication characterized by impaired trophoblast invasion and spiral artery remodeling and can have serious consequences for both mother and child. Protein phosphatase 1 regulatory subunit 3G (PPP1R3G) is involved in numerous tumor-related biological processes. However, the biological action and underlying mechanisms of PPP1R3G in PE progression remain unclear. We used western blotting and immunohistochemistry to investigate PPP1R3G expression in gestational age-matched pre-eclamptic and normal placental tissues. After lentivirus transfection, wound-healing, Transwell, cell-counting kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), and TdT mediateddUTP Nick End Labeling (TUNEL) assays were used to assess trophoblast migration, invasion, proliferation, and apoptosis, respectively. The relative expression levels of PPP1R3G and the proteins involved in the Akt signaling pathway were determined using western blotting. The results showed that PPP1R3G levels were significantly lower in the placental tissues and GSE74341 microarray of the PE group than those of the healthy control group. We also found that neonatal weight and Apgar score were lower at birth, and peak systolic blood pressure and diastolic blood pressure were higher in the PE group than in the non-PE group. In addition, PPP1R3G knockdown decreased p-Akt/Akt expression and inhibited migration, invasion, and proliferation in HTR-8/SVneo trophoblasts but had no discernible effect on cell apoptosis. Furthermore, PPP1R3G positively regulated matrix metallopeptidase 9 (MMP-9), which was downregulated in placental tissues of pregnant women with PE. These results provided the first evidence that the reduced levels of PPP1R3G might contribute to PE by suppressing the invasion and migration of trophoblasts and targeting the Akt/MMP-9 signaling pathway.

5-Iodotubercidin sensitizes cells to RIPK1-dependent necroptosis by interfering with NFκB signaling

Receptor-interacting protein kinases (RIPK)-1 and -3 play crucial roles in cell fate decisions and are regulated by multiple checkpoint controls. Previous studies have identified IKK1/2- and p38/MK2-dependent checkpoints that phosphorylate RIPK1 at different residues to inhibit its activation. In this study, we investigated TNF-induced death in MAPK-activated protein kinase 2 (MK2)-deficient cells and found that MK2 deficiency or inactivation predominantly leads to necroptotic cell death, even without caspase inhibition. While RIPK1 inhibitors can rescue MK2-deficient cells from necroptosis, inhibiting RIPK3 seems to switch the process to apoptosis. To understand the underlying mechanism of this switch, we screened a library of 149 kinase inhibitors and identified the adenosine analog 5-Iodotubercidin (5-ITu) as the most potent compound that sensitizes MK2-deficient MEFs to TNF-induced cell death. 5-ITu also enhances LPS-induced necroptosis when combined with MK2 inhibition in RAW264.7 macrophages. Further mechanistic studies revealed that 5-ITu induces RIPK1-dependent necroptosis by suppressing IKK signaling in the absence of MK2 activity. These findings highlight the role for the multitarget kinase inhibitor 5-ITu in TNF-, LPS- and chemotherapeutics-induced necroptosis and its potential implications in RIPK1-targeted therapies.

Cell death checkpoints in the TNF pathway

Tumor necrosis factor (TNF) plays a central role in orchestrating mammalian inflammatory responses. It promotes inflammation either directly by inducing inflammatory gene expression or indirectly by triggering cell death. TNF-mediated cell death-driven inflammation can be beneficial during infection by providing cell-extrinsic signals that help to mount proper immune responses. Uncontrolled cell death caused by TNF is instead highly detrimental and is believed to cause several human autoimmune diseases. Death is not the default response to TNF sensing. Molecular brakes, or cell death checkpoints, actively repress TNF cytotoxicity to protect the organism from its detrimental consequences. These checkpoints therefore constitute essential safeguards against inflammatory diseases. Recent advances in the field have revealed the existence of several new and unexpected brakes against TNF cytotoxicity and pathogenicity.

RIPK1 in the inflammatory response and sepsis: Recent advances, drug discovery and beyond

Cytokine storms are an important mechanism of sepsis. TNF-α is an important cytokine. As a regulator of TNF superfamily receptors, RIPK1 not only serves as the basis of the scaffold structure in complex I to promote the activation of the NF-κB and MAPK pathways but also represents an important protein in complex II to promote programmed cell death. Ubiquitination of RIPK1 is an important regulatory function that determines the activation of cellular inflammatory pathways or the activation of death pathways. In this paper, we introduce the regulation of RIPK1, RIPK1 PANoptosome's role in Inflammatory and sepsis, and perspectives.

Targeting Cell Membranes, Depleting ROS by Dithiane and Thioketal-Containing Polymers with Pendant Cholesterols Delivering Necrostatin-1 for Glaucoma Treatment

Glaucoma is the leading cause of irreversible blindness worldwide, characterized by progressive vision loss due to the selective damage to retinal ganglion cells (RGCs) and their axons. Oxidative stress is generally believed as one key factor of RGCs death. Recently, necroptosis was identified to play a key role in glaucomatous injury. Therefore, depletion of reactive oxygen species (ROS) and inhibition of necroptosis in RGCs has become one of treatment strategies for glaucoma. However, existing drugs without efficient drug enter into the retina and have controlled release due to a short drug retention. Herein, we designed a glaucomatous microenvironment-responsive drug carrier polymer, which is characterized by the presence of thioketal bonds and 1,4-dithiane unit in the main chain for depleting ROS as well as the pendant cholesterols for targeting cell membranes. This polymer was adopted to encapsulate an inhibitor of necroptosis, necrostatin-1, into nanoparticles (designated as NP1). NP1 with superior biosafety could scavenge ROS in RGCs both in vitro and in vivo of an acute pathological glaucomatous injury model. Further, NP1 was found to effectively inhibit the upregulation of the necroptosis pathway, reducing the death of RGCs. The findings in this study exemplified the use of nanomaterials as potential strategies to treat glaucoma.

RIP1 post-translational modifications

Receptor interacting protein 1 (RIP1) kinase is a critical regulator of inflammation and cell death signaling, and plays a crucial role in maintaining immune responses and proper tissue homeostasis. Mounting evidence argues for the importance of RIP1 post-translational modifications in control of its function. Ubiquitination by E3 ligases, such as inhibitors of apoptosis (IAP) proteins and LUBAC, as well as the reversal of these modifications by deubiquitinating enzymes, such as A20 and CYLD, can greatly influence RIP1 mediated signaling. In addition, cleavage by caspase-8, RIP1 autophosphorylation, and phosphorylation by a number of signaling kinases can greatly impact cellular fate. Disruption of the tightly regulated RIP1 modifications can lead to signaling disbalance in TNF and/or TLR controlled and other inflammatory pathways, and result in severe human pathologies. This review will focus on RIP1 and its many modifications with an emphasis on ubiquitination, phosphorylation, and cleavage, and their functional impact on the RIP1's role in signaling pathways.