PDK1, the master regulator of AGC kinase signal transduction

Proteomic approaches for protein kinase substrate identification in Apicomplexa

Apicomplexa is a phylum of protist parasites, notable for causing life-threatening diseases including malaria, toxoplasmosis, cryptosporidiosis, and babesiosis. Apicomplexan pathogenesis is generally a function of lytic replication, dissemination, persistence, host cell modification, and immune subversion. Decades of research have revealed essential roles for apicomplexan protein kinases in establishing infections and promoting pathogenesis. Protein kinases modify their substrates by phosphorylating serine, threonine, tyrosine, or other residues, resulting in rapid functional changes in the target protein. Post-translational modification by phosphorylation can activate or inhibit a substrate, alter its localization, or promote interactions with other proteins or ligands. Deciphering direct kinase substrates is crucial to understand mechanisms of kinase signaling, yet can be challenging due to the transient nature of kinase phosphorylation and potential for downstream indirect phosphorylation events. However, with recent advances in proteomic approaches, our understanding of kinase function in Apicomplexa has improved dramatically. Here, we discuss methods that have been used to identify kinase substrates in apicomplexan parasites, classifying them into three main categories: i) kinase interactome, ii) indirect phosphoproteomics and iii) direct labeling. We briefly discuss each approach, including their advantages and limitations, and highlight representative examples from the Apicomplexa literature. Finally, we conclude each main category by introducing prospective approaches from other fields that would benefit kinase substrate identification in Apicomplexa.

Targeting Smurf1 to block PDK1-Akt signaling in KRAS-mutated colorectal cancer

The phosphoinositide 3-kinase (PI3K)-Akt axis is one of the most frequently activated pathways and is demonstrated as a therapeutic target in Kirsten rat sarcoma viral oncogene homolog (KRAS)-mutated colorectal cancer (CRC). Targeting the PI3K-Akt pathway has been a challenging undertaking through the decades. Here we unveiled an essential role of E3 ligase SMAD ubiquitylation regulatory factor 1 (Smurf1)-mediated phosphoinositide-dependent protein kinase 1 (PDK1) neddylation in PI3K-Akt signaling and tumorigenesis. Upon growth factor stimulation, Smurf1 immediately triggers PDK1 neddylation and the poly-neural precursor cell expressed developmentally downregulated protein 8 (poly-Nedd8) chains recruit methyltransferase SET domain bifurcated histone lysine methyltransferase 1 (SETDB1). The cytoplasmic complex of PDK1 assembled with Smurf1 and SETDB1 (cCOMPASS) consisting of PDK1, Smurf1 and SETDB1 directs Akt membrane attachment and T308 phosphorylation. Smurf1 deficiency dramatically reduces CRC tumorigenesis in a genetic mouse model. Furthermore, we developed a highly selective Smurf1 degrader, Smurf1-antagonizing repressor of tumor 1, which exhibits efficient PDK1-Akt blockade and potent tumor suppression alone or combined with PDK1 inhibitor in KRAS-mutated CRC. The findings presented here unveil previously unrecognized roles of PDK1 neddylation and offer a potential strategy for targeting the PI3K-Akt pathway and KRAS mutant cancer therapy.

Partially knocking out NtPDK1a/1b/1c/1d simultaneously in Nicotiana tabacum using CRISPR/CAS9 technology results in auxin-related developmental defects

The eukaryotic AGC protein kinase subfamily (protein kinase A/ protein kinase G/ protein kinase C-family) is involved in regulating numerous biological processes across kingdoms, including growth and development, and apoptosis. PDK1(3-phosphoinositide-dependent protein kinase 1) is a conserved serine/threonine kinase in eukaryotes, which is both a member of AGC kinase and a major regulator of many other downstream AGC protein kinase family members. Although extensively investigated in model plant Arabidopsis, detailed reports for tobacco PDK1s have been limited. To better understand the functions of PDK1s in tobacco, CRISPR/CAS9 transgenic lines were generated in tetraploid N. tabacum, cv. Samsun (NN) with 5-7 of the 8 copies of 4 homologous PDK1 genes in tobacco genome (NtPDK1a/1b/1c/1d homologs) simultaneously knocked out. Numerous developmental defects were observed in these NtPDK1a/1b/1c/1d CRISPR/CAS9 lines, including cotyledon fusion leaf shrinkage, uneven distribution of leaf veins, convex veins, root growth retardation, and reduced fertility, all of which reminiscence of impaired polar auxin transport. The severity of these defects was correlated with the number of knocked out alleles of NtPDK1a/1b/1c/1d. Consistent with the observation in Arabidopsis, it was found that the polar auxin transport, and not auxin biosynthesis, was significantly compromised in these knockout lines compared with the wild type tobacco plants. The fact that no homozygous plant with all 8 NtPDK1a/1b/1c/1d alleles being knocked out suggested that knocking out 8 alleles of NtPDK1a/1b/1c/1d could be lethal. In conclusion, our results indicated that NtPDK1s are versatile AGC kinases that participate in regulation of tobacco growth and development via modulating polar auxin transport. Our results also indicated that CRISPR/CAS9 technology is a powerful tool in resolving gene redundancy in polyploidy plants.

SPARK regulates AGC kinases central to the Toxoplasma gondii asexual cycle

Apicomplexan parasites balance proliferation, persistence, and spread in their metazoan hosts. AGC kinases, such as PKG, PKA, and the PDK1 ortholog SPARK, integrate environmental signals to toggle parasites between replicative and motile life stages. Recent studies have cataloged pathways downstream of apicomplexan PKG and PKA; however, less is known about the global integration of AGC kinase signaling cascades. Here, conditional genetics coupled to unbiased proteomics demonstrates that SPARK complexes with an elongin-like protein to regulate the stability of PKA and PKG in the model apicomplexan Toxoplasma gondii. Defects attributed to SPARK depletion develop after PKG and PKA are down-regulated. Parasites lacking SPARK differentiate into the chronic form of infection, which may arise from reduced activity of a coccidian-specific PKA ortholog. This work delineates the signaling topology of AGC kinases that together control transitions within the asexual cycle of this important family of parasites.

Regulatory role of AGC genes in heat stress adaptation in maize (Zea mays)

Heat stress represents a significant environmental challenge that restricts maize (Zea mays ) growth and yield on a global scale. Within the plant kingdom, the AGC gene family, encoding a group of protein kinases, has emerged as crucial players in various stress responses. Nevertheless, a comprehensive understanding of AGC genes in Z. mays under heat-stress conditions remains elusive. A genome-wide analysis was done using bioinformatics techniques to identify 39 AGC genes in Z. mays , categorising them into three subfamilies based on their conserved domains. We investigated their phylogenetic relationships, gene structures (including intron-exon configurations), and expression patterns. These genes are likely involved in diverse signalling pathways, fulfilling distinct roles when exposed to heat stress conditions. Notably, most ZmAGC1.5, ZmAGC1.9, ZmNDR3, ZmNDR5 and ZmIRE3 exhibited significant changes in expression levels under heat stress, featuring a high G-box ratio. Furthermore, we pinpointed a subset of AGC genes displaying highly coordinated expression, implying their potential involvement in the heat stress response pathway. Our study offers valuable insights into the contribution of AGC genes to Z. mays 's heat stress response, thus facilitating the development of heat-tolerant Z. mays varieties.

A novel bivalent interaction mode underlies a non-catalytic mechanism for Pin1-mediated protein kinase C regulation

Regulated hydrolysis of the phosphoinositide phosphatidylinositol(4,5)-bis-phosphate to diacylglycerol and inositol-1,4,5-P3 defines a major eukaryotic pathway for translation of extracellular cues to intracellular signaling circuits. Members of the lipid-activated protein kinase C isoenzyme family (PKCs) play central roles in this signaling circuit. One of the regulatory mechanisms employed to downregulate stimulated PKC activity is via a proteasome-dependent degradation pathway that is potentiated by peptidyl-prolyl isomerase Pin1. Here, we show that contrary to prevailing models, Pin1 does not regulate conventional PKC isoforms α and βII via a canonical cis-trans isomerization of the peptidyl-prolyl bond. Rather, Pin1 acts as a PKC binding partner that controls PKC activity via sequestration of the C-terminal tail of the kinase. The high-resolution structure of full-length Pin1 complexed to the C-terminal tail of PKCβII reveals that a novel bivalent interaction mode underlies the non-catalytic mode of Pin1 action. Specifically, Pin1 adopts a conformation in which it uses the WW and PPIase domains to engage two conserved phosphorylated PKC motifs, the turn motif and hydrophobic motif, respectively. Hydrophobic motif is a non-canonical Pin1-interacting element. The structural information combined with the results of extensive binding studies and experiments in cultured cells suggest that non-catalytic mechanisms represent unappreciated modes of Pin1-mediated regulation of AGC kinases and other key enzymes/substrates.

Artesunate improves glucose and lipid metabolism in db/db mice by regulating the metabolic profile and the MAPK/PI3K/Akt signalling pathway

BACKGROUND

Diabetes is a metabolic disorder characterized by chronic hyperglycaemia. Chronic metabolic abnormalities and long-term hyperglycaemia may result in a wide range of acute and chronic consequences. Previous studies have demonstrated that artesunate(ART) has antidiabetic, anti-inflammatory, antiatherosclerotic, and other beneficial effects, but the specific regulatory mechanism is not completely clear.

AIM

This study investigated the effects of ART on metabolic disorders in type 2 diabetes mellitus (T2DM) model db/db mice and explored the underlying mechanisms involved.

METHODS

C57BL/KsJ-db/db mice were used to identify the targets and molecular mechanism of ART. Metabolomic methods were used to evaluate the efficacy of ART in improving T2DM-related metabolic disorders. Network pharmacology and transcriptomic sequencing were used to analyse the targets and pathways of ART in T2DM. Finally, molecular biology experiments were performed to verify the key targets and pathways selected by network pharmacology and transcriptomic analyses.

RESULTS

After a 7-week ART intervention (160 mg/kg), the glucose and lipid metabolism levels of the db/db mice improved. Additionally, the oxidative stress indices, namely, the MDA and SOD levels, significantly improved (p<0.01). Linoleic acid and glycerophospholipid metabolism, amino acid metabolism, bile acid synthesis, and purine metabolism disorders in db/db mice were partially corrected after ART treatment. Network pharmacology analysis identified important targets of ART for the treatment of metabolic disorders in T2DM . These targets are involved in key signalling pathways, including the highest scores observed for the PI3K/Akt signalling pathway. Transcriptomic analysis revealed that ART could activate the MAPK signalling pathway and two key gene targets, HGK and GADD45. Immunoblotting revealed that ART increases p-PI3K, p-AKT, Glut2, and IRS1 protein expression and suppresses the phosphorylation of p38, ERK1/2, and JNK, returning HGK and GADD45 to their preartesunate levels.

CONCLUSION

Treatment of db/db mice with 160 mg/kg ART for 7 weeks significantly reduced fasting blood glucose and lipid levels. It also improved metabolic imbalances in amino acids, lipids, purines, and bile acids, thereby improving metabolic disorders. These effects are achieved by activating the PI3K/AKT pathway and inhibiting the MAPK pathway, thus demonstrating the efficacy of the drug.

Quercetin Limits Tumor Immune Escape through PDK1/CD47 Axis in Melanoma

Quercetin (3,3[Formula: see text],4[Formula: see text],5,7-pentahydroxyflavone) is a bioactive plant-derived flavonoid, abundant in fruits and vegetables, that can effectively inhibit the growth of many types of tumors without toxicity. Nevertheless, the effect of quercetin on melanoma immunology has yet to be determined. This study aimed to investigate the role and mechanism of the antitumor immunity action of quercetin in melanoma through both in vivo and in vitro methods. Our research revealed that quercetin has the ability to boost antitumor immunity by modulating the tumor immune microenvironment through increasing the percentages of M1 macrophages, CD8[Formula: see text] T lymphocytes, and CD4[Formula: see text] T lymphocytes and promoting the secretion of IL-2 and IFN-[Formula: see text] from CD8[Formula: see text] T cells, consequently suppressing the growth of melanoma. Furthermore, we revealed that quercetin can inhibit cell proliferation and migration of B16 cells in a dose-dependent manner. In addition, down-regulating PDK1 can inhibit the mRNA and protein expression levels of CD47. In the rescue experiment, we overexpressed PDK1 and found that the protein and mRNA expression levels of CD47 increased correspondingly, while the addition of quercetin reversed this effect. Moreover, quercetin could stimulate the proliferation and enhance the function of CD8[Formula: see text] T cells. Therefore, our results identified a novel mechanism through which CD47 is regulated by quercetin to promote phagocytosis, and elucidated the regulation of quercetin on macrophages and CD8[Formula: see text] T cells in the tumor immune microenvironment. The use of quercetin as a therapeutic drug holds potential benefits for immunotherapy, enhancing the efficacy of existing treatments for melanoma.

Advancements in dual-target inhibitors of PI3K for tumor therapy: Clinical progress, development strategies, prospects

Phosphoinositide 3-kinases (PI3Ks) modify lipids by the phosphorylation of inositol phospholipids at the 3'-OH position, thereby participating in signal transduction and exerting effects on various physiological processes such as cell growth, metabolism, and organism development. PI3K activation also drives cancer cell growth, survival, and metabolism, with genetic dysregulation of this pathway observed in diverse human cancers. Therefore, this target is considered a promising potential therapeutic target for various types of cancer. Currently, several selective PI3K inhibitors and one dual-target PI3K inhibitor have been approved and launched on the market. However, the majority of these inhibitors have faced revocation or voluntary withdrawal of indications due to concerns regarding their adverse effects. This article provides a comprehensive review of the structure and biological functions, and clinical status of PI3K inhibitors, with a specific emphasis on the development strategies and structure-activity relationships of dual-target PI3K inhibitors. The findings offer valuable insights and future directions for the development of highly promising dual-target drugs targeting PI3K.

Comparative proteomic analysis of cerebral cortex revealed neuroprotective mechanism of esculentoside A on Alzheimer's disease

Esculentoside A (EsA), isolated from phytolacca esculenta, is a saponin showing neuroprotective effect in the mouse models of Alzheimer's disease (AD). To investigate its action target and underlying mechanism, this study used the proteomics technique of isobaric tags for relative and absolute quantification (iTRAQ) to analyze the differentially expressed proteins (DEPs) in the cerebral cortex of EsA-treated and untreated triple-transgenic 3 × Tg-AD model mice. Proteomic comparison revealed 250, 436, and 903 DEPs in three group pairs, i.e. AD/Wild-type (WT), AD+5 mg/kg EsA/AD, AD+10 mg/kg EsA/AD, respectively. Among them 28 DEPs were commonly shared by three group pairs, and 25 of them showed reversed expression levels in the diseased group under the treatment of both doses of EsA. Bioinformatics analysis revealed that these DEPs were mainly linked to metabolism, synapses, apoptosis, learning and memory. EsA treatment restored the expression of these proteins, including amyloid precursor protein (APP), cathepsin B (Cstb), 4-aminobutyrate aminotransferase (Abat), 3-phosphoinositide-dependent protein kinase-1 (PDK1), carnitine palmitoyltransferase1 (Cpt1) and synaptotagmin 17 (Syt17), thereby ameliorated the spatial learning and memory of AD mice. Collectively, this study reveals for the first time the profound effect of EsA on the cerebral cortex of AD mice, which might be a potential therapeutic agent for the treatment of AD.

Glycaemic abnormalities induced by small molecule tryosine kinase inhibitors: a review

In light of the expected increase in the prevalence of diabetes mellitus due to an aging population, sedentary lifestyles, an increase in obesity, and unhealthy diets, there is a need to identify potential pharmacological agents that can heighten the risk of developing diabetes. Similarly, it is equally important to also identify those agents that show blood glucose-lowering properties. Amongst these agents are tyrosine kinase inhibitors used to treat certain types of cancers. Over the last two decades, there has been an increase in the use of targeted chemotherapy for cancers such as renal cell carcinoma, chronic leukaemia, and gastrointestinal stromal tumours. Small molecule tyrosine kinase inhibitors have been at the forefront of targeted chemotherapy. Studies have shown that small molecule tyrosine kinase inhibitors can alter glycaemic control and glucose metabolism, with some demonstrating hypoglycaemic activities whilst others showing hyperglycaemic properties. The mechanism by which small molecule tyrosine kinase inhibitors cause glycaemic dysregulation is not well understood, therefore, the clinical significance of these chemotherapeutic agents on glucose handling is also poorly documented. In this review, the effort is directed at mapping mechanistic insights into the effect of various small molecule tyrosine kinase inhibitors on glycaemic dysregulation envisaged to provide a deeper understanding of these chemotherapeutic agents on glucose metabolism. Small molecule tyrosine kinase inhibitors may elicit these observed glycaemic effects through preservation of β-cell function, improving insulin sensitivity and insulin secretion. These compounds bind to a spectrum of receptors and proteins implicated in glucose regulation for example, non-receptor tyrosine kinase SRC and ABL. Then receptor tyrosine kinase EGFR, PDGFR, and FGFR.

PI3K signaling promotes formation of lipid-laden foamy macrophages at the spinal cord injury site

After spinal cord injury (SCI), infiltrating macrophages undergo excessive phagocytosis of myelin and cellular debris, forming lipid-laden foamy macrophages. To understand their role in the cellular pathology of SCI, investigation of the foamy macrophage phenotype in vitro revealed a pro-inflammatory profile, increased reactive oxygen species (ROS) production, and mitochondrial dysfunction. Bioinformatic analysis identified PI3K as a regulator of inflammation in foamy macrophages, and inhibition of this pathway decreased their lipid content, inflammatory cytokines, and ROS production. Macrophage-specific inhibition of PI3K using liposomes significantly decreased foamy macrophages at the injury site after a mid-thoracic contusive SCI in mice. RNA sequencing and in vitro analysis of foamy macrophages revealed increased autophagy and decreased phagocytosis after PI3K inhibition as potential mechanisms for reduced lipid accumulation. Together, our data suggest that the formation of pro-inflammatory foamy macrophages after SCI is due to the activation of PI3K signaling, which increases phagocytosis and decreases autophagy.

Modulating the PI3K Signalling Pathway in Activated PI3K Delta Syndrome: a Clinical Perspective

Activated phosphoinositide-3-kinase (PI3K) δ syndrome (APDS) is an inborn error of immunity characterised by immune dysregulation. Since the discovery of genetic mutations resulting in PI3Kδ overactivation, treatment of APDS patients has begun to focus on modulation of the PI3K pathway in addition to supportive therapies. The mTOR inhibitor sirolimus has been used effectively for some clinical manifestations of this condition, however the arrival of specific PI3Kδ inhibitor leniolisib has shown promising early results and may provide a more targeted approach. This review summarizes key aspects of PI3K pathway biology and discusses potential options for nuanced modulation of the PI3K pathway in APDS from a clinical perspective, highlighting differences from PI3K inhibition in haematological malignancies.

A novel small molecule, CU05-1189, targeting the pleckstrin homology domain of PDK1 suppresses VEGF-mediated angiogenesis and tumor growth by blocking the Akt signaling pathway

Inhibition of angiogenesis is considered a promising therapeutic approach for cancer treatment. Our previous genetic research showed that the use of a cell-penetrating peptide to inhibit the pleckstrin homology (PH) domain of 3-phosphoinositide-dependent kinase 1 (PDK1) was a viable approach to suppress pathological angiogenesis. Herein, we synthesized and characterized a novel small molecule, CU05-1189, based on our prior study and present evidence for the first time that this compound possesses antiangiogenic properties both in vitro and in vivo. The computational analysis showed that CU05-1189 can interact with the PH domain of PDK1, and it significantly inhibited vascular endothelial growth factor (VEGF)-induced proliferation, migration, invasion, and tube formation in human umbilical vein endothelial cells without apparent toxicity. Western blot analysis revealed that the Akt signaling pathway was specifically inhibited by CU05-1189 upon VEGF stimulation, without affecting other VEGF receptor 2 downstream molecules or cytosolic substrates of PDK1, by preventing translocation of PDK1 to the plasma membrane. We also found that CU05-1189 suppressed VEGF-mediated vascular network formation in a Matrigel plug assay. More importantly, CU05-1189 had a good pharmacokinetic profile with a bioavailability of 68%. These results led to the oral administration of CU05-1189, which resulted in reduced tumor microvessel density and growth in a xenograft mouse model. Taken together, our data suggest that CU05-1189 may have great potential and be a promising lead as a novel antiangiogenic agent for cancer treatment.

Role of gut commensal bacteria in juvenile developmental growth of the host: insights from Drosophila studies

The gut microbiome plays a crucial role in maintaining health in a variety of organisms, from insects to humans. Further, beneficial symbiotic microbes are believed to contribute to improving the quality of life of the host. Drosophila is an optimal model for studying host-commensal microbe interactions because it allows for convenient manipulation of intestinal microbial composition. Fly microbiota has a simple taxonomic composition and can be cultivated and genetically tracked. This permits functional studies and analyses of the molecular mechanisms underlying their effects on host physiological processes. In this context, we briefly introduce the principle of juvenile developmental growth in Drosophila. Then, we discuss the current understanding of the molecular mechanisms underlying the effects of gut commensal bacteria, such as Lactiplantibacillus plantarum and Acetobacter pomorum, in the fly gut microbiome on Drosophila juvenile growth, including specific actions of gut hormones and metabolites in conserved cellular signaling systems, such as the insulin/insulin-like (IIS) and the target of rapamycin (TOR) pathways. Given the similarities in tissue function/structure, as well as the high conservation of physiological systems between Drosophila and mammals, findings from the Drosophila model system will have significant implications for understanding the mechanisms underlying the interaction between the host and the gut microbiome in metazoans.

Master kinase PDK1 in tumorigenesis

3-phosphoinositide-dependent protein kinase 1 (PDK1) is considered as master kinase regulating AGC kinase family members such as AKT, SGK, PLK, S6K and RSK. Although autophosphorylation regulates PDK1 activity, accumulating evidence suggests that PDK1 is manipulated by many other mechanisms, including S6K-mediated phosphorylation, and the E3 ligase SPOP-mediated ubiquitination and degradation. Dysregulation of these upstream regulators or downstream signals involves in cancer development, as PDK1 regulating cell growth, metastasis, invasion, apoptosis and survival time. Meanwhile, overexpression of PDK1 is also exposed in a plethora of cancers, whereas inhibition of PDK1 reduces cell size and inhibits tumor growth and progression. More importantly, PDK1 also modulates the tumor microenvironments and markedly influences tumor immunotherapies. In summary, we comprehensively summarize the downstream signals, upstream regulators, mouse models, inhibitors, tumor microenvironment and clinical treatments for PDK1, and highlight PDK1 as a potential cancer therapeutic target.

A novel bivalent interaction mode underlies a non-catalytic mechanism for Pin1-mediated Protein Kinase C regulation

Regulated hydrolysis of the phosphoinositide phosphatidylinositol(4,5)-bis-phosphate to diacylglycerol and inositol-1,4,5-P3 defines a major eukaryotic pathway for translation of extracellular cues to intracellular signaling circuits. Members of the lipid-activated protein kinase C isoenzyme family (PKCs) play central roles in this signaling circuit. One of the regulatory mechanisms employed to downregulate stimulated PKC activity is via a proteasome-dependent degradation pathway that is potentiated by peptidyl-prolyl isomerase Pin1. Here, we show that contrary to prevailing models, Pin1 does not regulate conventional PKC isoforms α and βII via a canonical cis-trans isomerization of the peptidyl-prolyl bond. Rather, Pin1 acts as a PKC binding partner that controls PKC activity via sequestration of the C-terminal tail of the kinase. The high-resolution structure of Pin1 complexed to the C-terminal tail of PKCβII reveals that a novel bivalent interaction mode underlies the non-catalytic mode of Pin1 action. Specifically, Pin1 adopts a compact conformation in which it engages two conserved phosphorylated PKC motifs, the turn motif and hydrophobic motif, the latter being a non-canonical Pin1-interacting element. The structural information, combined with the results of extensive binding studies and in vivo experiments suggest that non-catalytic mechanisms represent unappreciated modes of Pin1-mediated regulation of AGC kinases and other key enzymes/substrates.

Iguratimod suppresses Tfh cell differentiation in primary Sjögren's syndrome patients through inhibiting Akt/mTOR/STAT3 signaling

BACKGROUND

Iguratimod (IGU) reduces hypergammaglobulinemia and disease activity in pSS (primary Sjögren's syndrome) patients. However, the therapeutical mechanism of IGU for pSS remains largely unknown. This study aimed to investigate the regulation of Tfh cell differentiation by IGU in pSS patients.

METHODS

We prospectively enrolled 13 pSS patients treated with IGU for 3 months and examined circulating T cell and B cell subsets by flow cytometry. We measured Tfh cell differentiation treated by IGU in pSS patients and healthy controls. Transcriptome analysis combined with molecular docking were employed to identify potential therapeutical targets of IGU, which were verified by Western blot and Tfh cell differentiation.

RESULTS

Tfh, plasmablast, and plasma cells were suppressed by IGU treatment at 1 and 3 months. Tfh cell differentiation and function were significant inhibited by IGU in pSS patients and healthy controls in vitro. Pyruvate dehydrogenase kinase 1 (PDK1) was identified as a target of IGU during Tfh cell differentiation, and the downstream Akt phosphorylation was attenuated by IGU. Moreover, the activity of mTORC1 and phosphorylation of STAT3 were suppressed by IGU, with downregulation of BCL6 and upregulation of PRDM1. Finally, Akt activator restored IGU-suppressed Tfh cell differentiation.

CONCLUSIONS

IGU suppresses Tfh cell differentiation in pSS patients through interacting with PDK1 and suppressing Akt-mTOR-STAT3 signaling.

AMIGO2 attenuates innate cisplatin sensitivity by suppression of GSDME-conferred pyroptosis in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) accounts for approximately 85% of lung cancer. Cisplatin is commonly used in the treatment of many malignant tumours including NSCLC. The innate drug sensitivity greatly affects the clinical efficacy of cisplatin-based chemotherapy. As a plasma membrane adhesion molecule, amphoterin-induced gene and ORF-2 (AMIGO2) initially identified as a neurite outgrowth factor has been recently found to play a crucial role in cancer occurrence and progression. However, it is still unclear whether AMIGO2 is involved in innate cisplatin sensitivity. In the present study, we provided the in vitro and in vivo evidences indicating that the alteration of AMIGO2 expression triggered changes of innate cisplatin sensitivity as well as cisplatin-induced pyroptosis in NSCLC. Further results revealed that AMIGO2 might inhibit cisplatin-induced activation of (caspase-8 and caspase-9)/caspase-3 via stimulating PDK1/Akt (T308) signalling axis, resulting in suppression of GSDME cleavage and the subsequent cell pyroptosis, thereby decreasing the sensitivity of NSCLC cells to cisplatin treatment. The results provided a new insight that AMIGO2 regulated the innate cisplatin sensitivity of NSCLC through GSDME-mediated pyroptosis.

High fat diet allows food-predictive stimuli to energize action performance in the absence of hunger, without distorting insulin signaling on accumbal cholinergic interneurons

Obesity can disrupt how food-predictive stimuli control action performance and selection. These two forms of control recruit cholinergic interneurons (CIN) located in the nucleus accumbens core (NAcC) and shell (NAcS), respectively. Given that obesity is associated with insulin resistance in this region, we examined whether interfering with CIN insulin signaling disrupts how food-predictive stimuli control actions. To interfere with insulin signaling we used a high-fat diet (HFD) or genetic excision of insulin receptor (InsR) from cholinergic cells. HFD left intact the capacity of food-predictive stimuli to energize performance of an action earning food when mice were tested hungry. However, it allowed this energizing effect to persist when the mice were tested sated. This persistence was linked to NAcC CIN activity but was not associated with distorted CIN insulin signaling. Accordingly, InsR excision had no effect on how food-predicting stimuli control action performance. Next, we found that neither HFD nor InsR excision altered the capacity of food-predictive stimuli to guide action selection. Yet, this capacity was associated with changes in NAcS CIN activity. These results indicate that insulin signaling on accumbal CIN does not modulate how food-predictive stimuli control action performance and selection. However, they show that HFD allows food-predictive stimuli to energize performance of an action earning food in the absence of hunger.

Food Polyphenols and Type II Diabetes Mellitus: Pharmacology and Mechanisms

Type II diabetes mellitus and its related complications are growing public health problems. Many natural products present in our diet, including polyphenols, can be used in treating and managing type II diabetes mellitus and different diseases, owing to their numerous biological properties. Anthocyanins, flavonols, stilbenes, curcuminoids, hesperidin, hesperetin, naringenin, and phenolic acids are common polyphenols found in blueberries, chokeberries, sea-buckthorn, mulberries, turmeric, citrus fruits, and cereals. These compounds exhibit antidiabetic effects through different pathways. Accordingly, this review presents an overview of the most recent developments in using food polyphenols for managing and treating type II diabetes mellitus, along with various mechanisms. In addition, the present work summarizes the literature about the anti-diabetic effect of food polyphenols and evaluates their potential as complementary or alternative medicines to treat type II diabetes mellitus. Results obtained from this survey show that anthocyanins, flavonols, stilbenes, curcuminoids, and phenolic acids can manage diabetes mellitus by protecting pancreatic β-cells against glucose toxicity, promoting β-cell proliferation, reducing β-cell apoptosis, and inhibiting α-glucosidases or α-amylase. In addition, these phenolic compounds exhibit antioxidant anti-inflammatory activities, modulate carbohydrate and lipid metabolism, optimize oxidative stress, reduce insulin resistance, and stimulate the pancreas to secrete insulin. They also activate insulin signaling and inhibit digestive enzymes, regulate intestinal microbiota, improve adipose tissue metabolism, inhibit glucose absorption, and inhibit the formation of advanced glycation end products. However, insufficient data are available on the effective mechanisms necessary to manage diabetes.

The Pathogenesis of Diabetes

Diabetes is the most common metabolic disorder, with an extremely serious effect on health systems worldwide. It has become a severe, chronic, non-communicable disease after cardio-cerebrovascular diseases. Currently, 90% of diabetic patients suffer from type 2 diabetes. Hyperglycemia is the main hallmark of diabetes. The function of pancreatic cells gradually declines before the onset of clinical hyperglycemia. Understanding the molecular processes involved in the development of diabetes can provide clinical care with much-needed updates. This review provides the current global state of diabetes, the mechanisms involved in glucose homeostasis and diabetic insulin resistance, and the long-chain non-coding RNA (lncRNA) associated with diabetes.

Phosphorylation of LKB1 by PDK1 Inhibits Cell Proliferation and Organ Growth by Decreased Activation of AMPK

The master kinase LKB1 is a key regulator of se veral cellular processes, including cell proliferation, cell polarity and cellular metabolism. It phosphorylates and activates several downstream kinases, including AMP-dependent kinase, AMPK. Activation of AMPK by low energy supply and phosphorylation of LKB1 results in an inhibition of mTOR, thus decreasing energy-consuming processes, in particular translation and, thus, cell growth. LKB1 itself is a constitutively active kinase, which is regulated by posttranslational modifications and direct binding to phospholipids of the plasma membrane. Here, we report that LKB1 binds to Phosphoinositide-dependent kinase (PDK1) by a conserved binding motif. Furthermore, a PDK1-consensus motif is located within the kinase domain of LKB1 and LKB1 gets phosphorylated by PDK1 in vitro. In Drosophila, knockin of phosphorylation-deficient LKB1 results in normal survival of the flies, but an increased activation of LKB1, whereas a phospho-mimetic LKB1 variant displays decreased AMPK activation. As a functional consequence, cell growth as well as organism size is decreased in phosphorylation-deficient LKB1. Molecular dynamics simulations of PDK1-mediated LKB1 phosphorylation revealed changes in the ATP binding pocket, suggesting a conformational change upon phosphorylation, which in turn can alter LKB1's kinase activity. Thus, phosphorylation of LKB1 by PDK1 results in an inhibition of LKB1, decreased activation of AMPK and enhanced cell growth.

Phosphoproteomics Profiling Defines a Target Landscape of the Basophilic Protein Kinases AKT, S6K, and RSK in Skeletal Myotubes

Phosphorylation-dependent signal transduction plays an important role in regulating the functions and fate of skeletal muscle cells. Central players in the phospho-signaling network are the protein kinases AKT, S6K, and RSK as part of the PI3K-AKT-mTOR-S6K and RAF-MEK-ERK-RSK pathways. However, despite their functional importance, knowledge about their specific targets is incomplete because these kinases share the same basophilic substrate motif RxRxxp[ST]. To address this, we performed a multifaceted quantitative phosphoproteomics study of skeletal myotubes following kinase inhibition. Our data corroborate a cross talk between AKT and RAF, a negative feedback loop of RSK on ERK, and a putative connection between RSK and PI3K signaling. Altogether, we report a kinase target landscape containing 49 so far unknown target sites. AKT, S6K, and RSK phosphorylate numerous proteins involved in muscle development, integrity, and functions, and signaling converges on factors that are central for the skeletal muscle cytoskeleton. Whereas AKT controls insulin signaling and impinges on GTPase signaling, nuclear signaling is characteristic for RSK. Our data further support a role of RSK in glucose metabolism. Shared targets have functions in RNA maturation, stability, and translation, which suggests that these basophilic kinases establish an intricate signaling network to orchestrate and regulate processes involved in translation.

Exploration the role of INHBA in Hu sheep granulosa cells using RNA-Seq

Activin/inhibin is an important factor for the fecundity of Hu sheep, and it is involved in follicular development in ovaries. Inhibin subunit beta A (INHBA) participates in the synthesis of activin A and inhibin A. In this study, we also noted a positive correlation between INHBA level and the secretion of both activin A and inhibin A in culture medium. Nevertheless, both knockdown and overexpression of INHBA downregulated the expression of Inhibin Subunit Alpha (INHA). Based on RNA-Sequencing, we further examined the effect and molecular mechanism of INHBA knockdown in GCs on mRNA expression. A total of 1,687 differentially expressed genes (DEGs) were identified (Fold change ≥ 2; False-discovory-rates (FDR) ≤ 0.01), of which 602 genes were upregulated and 1,087 genes were downregulated in the INHBA interference group compared with the control groups. Gene Ontology (GO) enrichment indicated that these DEGs were mainly involved in the regulation of cell cycle, protein serine/threonine kinase activity, and actin cytoskeleton reorganization. Moreover, DEGs were significantly enriched in 40 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, including P53, progesterone-mediated oocyte maturation, and PI3K-AKT signaling pathways. We also noted a positive correlation between INHBA level and many PI3K/Akt/mTOR pathway-related genes at the gene or/and protein expression. Overall, this study may contribute to a better understanding of the roles of INHBA on GCs of prolific sheep, as well as the molecular effect of low INHBA expression on GCs, clarifying some reproductive failures.

Activation of long-non-coding RNA NEAT1 sponging microRNA-147 inhibits radiation damage by targeting PDPK1 in troxerutin radioprotection

A better understanding of the molecular mechanism involving the lncRNA-miRNA-mRNA network underlying radiation damage can be beneficial for radioprotection. This study was designed to investigate the potential role of lncRNA NEAT1, miR-147 and Phosphoinositide Dependent Protein Kinase 1 (PDPK1) interaction in radioprotection by troxerutin (TRT). We first demonstrated that NEAT1 sponged miR-147, and PDPK1 mRNA was the primary target of miR-147. In the cells, the NEAT1 and PDPK1 levels were downregulated after the radiation but increased after the treatment with TRT. The miR-147 level was significantly induced by radiation and inhibited by TRT. NEAT1 negatively regulated the expression of miR-147, whereas miR-47 targeted PDPK1 to downregulate its expression. In radioprotection, TRT effectively upregulated NEAT1 to inhibit miR-147 and to upregulate PDPK1. We concluded that TRT could promote radioprotection by stimulating NEAT1 to upregulate PDPK1 expression by suppressing miR-147. NEAT1 could be a critical therapeutic target of radiation damage.

Salmonella effector SopF regulates PANoptosis of intestinal epithelial cells to aggravate systemic infection

SopF, a newly discovered effector secreted by Salmonella pathogenicity island-1 type III secretion system (T3SS1), was reported to target phosphoinositide on host cell membrane and aggravate systemic infection, while its functional relevance and underlying mechanisms have yet to be elucidated. PANoptosis (pyroptosis, apoptosis, and necroptosis) of intestinal epithelial cells (IECs) has been characterized as a pivotal host defense to limit the dissemination of foodborne pathogens, whereas the effect of SopF on IECs PANoptosis induced by Salmonella is rather limited. Here, we show that SopF can attenuate intestinal inflammation and suppress IECs expulsion to promote bacterial dissemination in mice infected with Salmonella enterica serovar Typhimurium (S. Typhimurium). We revealed that SopF could activate phosphoinositide-dependent protein kinase-1 (PDK1) to phosphorylate p90 ribosomal S6 kinase (RSK) which down-regulated Caspase-8 activation. Caspase-8 inactivated by SopF resulted in inhibition of pyroptosis and apoptosis, but promotion of necroptosis. The administration of both AR-12 (PDK1 inhibitor) and BI-D1870 (RSK inhibitor) potentially overcame Caspase-8 blockade and subverted PANoptosis challenged by SopF. Collectively, these findings demonstrate that this virulence strategy elicited by SopF aggregates systemic infection via modulating IEC PANoptosis through PDK1-RSK signaling, which throws light on novel functions of bacterial effectors, as well as a mechanism employed by pathogens to counteract host immune defense.

The Warburg effect in osteoporosis: Cellular signaling and epigenetic regulation of energy metabolic events to targeting the osteocalcin for phenotypic alteration

Osteoporosis is a silent disease of skeletal morphology that induces fragility and fracture risk in aged persons irrespective of gender. Juvenile secondary osteoporosis is rare and is influenced by familial genetic abnormalities. Despite the currently available therapeutic options, more-acute treatments are in need. Women suffer from osteoporosis after menopause, which is characterized by a decline in the secretion of sex hormones in the later phase of life. Several studies in the past two decades emphasized hormone-related pathways to combat osteoporosis. Some studies partially examined energy-related pathways, but achieving a more vivid picture of metabolism and bone remodeling in terms of the Warburg phenomenon is still warranted. Each cell requires sufficient energy for cellular propagation and growth; in particular, osteoporosis is an energy-dependent mechanism affected by a decreased cellular mass of the bone morphology. Energy utilization is the actual propagation of such diseases, and narrowing down these criteria will hopefully provide clues to formulate better therapeutic strategies. Oxidative glycolysis is a particular type of energy metabolic pathway in cancer cells that influences cellular proliferation. Therefore, the prospect of utilizing collective glucose metabolism by inducing the Warburg effect may improve cell propagation. The benefits of utilizing the energy from the Warburg effect may be a difficult task. However, it seems to improve their effectiveness in the osteoblast phenotype by connecting the selected pathways such as WNT, Notch, AKT, and Insulin signaling by targeting osteocalcin resulting in phenotypic alteration. Osteocalcin directs ATP utilization through the sclerostin SOST gene in the bone microenvironment. Thus, selective activation of ATP production involved in osteoblast maturation remains a prime strategy to fight osteoporosis.

Emerging Role of ERBB2 in Targeted Therapy for Metastatic Colorectal Cancer: Signaling Pathways to Therapeutic Strategies

Simple Summary

Colorectal cancer (CRC) is the third most commonly diagnosed malignancy and the second most common cause of cancer-related mortality worldwide. Currently available targeted therapies for metastatic CRC mainly target vascular endothelial growth factor and epidermal growth factor receptor in RAS wild-type tumors. Although Erb-B2 receptor tyrosine kinase 2 (ERBB2/human epidermal growth factor receptor 2) plays a significant therapeutic role in breast and gastric cancers, there are no licensed ERBB2-targeted therapies for metastatic CRC. This review aims to outline the molecular biology of ERBB2-positive metastatic CRC and potential targeted therapeutic strategies.

Abstract

Despite recent improvements in the comprehensive therapy of malignancy, metastatic colorectal cancer (mCRC) continues to have a poor prognosis. Notably, 5% of mCRC cases harbor Erb-B2 receptor tyrosine kinase 2 (ERBB2) alterations. ERBB2, commonly referred to as human epidermal growth factor receptor 2, is a member of the human epidermal growth factor receptor family of protein tyrosine kinases. In addition to being a recognized therapeutic target in the treatment of gastric and breast malignancies, it is considered crucial in the management of CRC. In this review, we describe the molecular biology of ERBB2 from the perspective of biomarkers for mCRC-targeted therapy, including receptor structures, signaling pathways, gene alterations, and their detection methods. We also discuss the relationship between ERBB2 aberrations and the underlying mechanisms of resistance to anti-EGFR therapy and immunotherapy tolerance in these patients with a focus on novel targeted therapeutics and ongoing clinical trials. This may aid the development of a new standard of care in patients with ERBB2-positive mCRC.

Novel active compounds and the anti-diabetic mechanism of mulberry leaves

Mulberry (Morus alba L.) leaves have long been considered beneficial in traditional Chinese medicine to treat infectious and internal diseases. Recently studies have discovered that the mulberry leaf’s total flavonoids (MLF) display excellent hypoglycemia properties. However, the active ingredients and their molecular mechanisms are still uncharacterized. In this study, we explored the hypoglycemic effects of MLF and mulberry leaf polysaccharides (MLP) on ob/ob mice, an animal model of type 2 diabetes mellitus (T2DM), compared with Ramulus Mori (Sangzhi) alkaloid (RMA). Network pharmacology was employed to identify the potential available targets and active compounds of MLF and RMA against hyperglycemia. Molecular docking, an insulin-resistant cell model and qPCR were employed to verify the antidiabetic activity of the critical compounds and the gene expression profiles of the top molecular targets. Here, the results showed that MLF and MLP improved glucose uptake in insulin-resistant hepatocytes. MLF, MLP and RMA alleviated insulin resistance and glucose intolerance in ob/ob mice. Unlike MLF and MLP, RMA administration did not influence the accumulation of intrahepatic lipids. Network pharmacology analysis revealed that morusin, kuwanon C and morusyunnansin L are the main active compounds of MLF and that they amend insulin resistance and glycemia via the PI3K- Akt signaling pathway, lipid and atherosclerosis pathways, and the AGE-RAGE signaling pathway. Moreover, 1-deoxynojirimycin (DNJ), fagomine (FA), and N-methyl-1-deoxynojirimycin are the primary active ingredients of RMA and target carbohydrate metabolism and regulate alpha-glucosidase activity to produce a potent anti-diabetic effect. The molecular docking results indicated that morusin, kuwanon C and morusyunnansin L are the critical bioactive compounds of MLF. They had high affinities with the key targets adenosine A1 receptor (ADORA1), AKT serine/threonine kinase 1 (AKT1), peroxisome proliferator-activated receptor gamma (PPARγ), and glycogen synthase kinase 3 beta (GSK3β), which play crucial roles in the MLF-mediated glucose-lowering effect. Additionally, morusin plays a role in amending insulin resistance of hepatocytes by repressing the expression of the ADORA1 and PPARG genes. Our results shed light on the mechanism behind the glucose-lowering effects of MLF, suggesting that morusin, kuwanon C, and morusyunnansin L might be promising drug leads for the management of T2DM.

Structural features of the protein kinase domain and targeted binding by small-molecule inhibitors

Protein kinases are key components in cellular signaling pathways as they carry out the phosphorylation of proteins, primarily on Ser, Thr, and Tyr residues. The catalytic activity of protein kinases is regulated, and they can be thought of as molecular switches that are controlled through protein-protein interactions and post-translational modifications. Protein kinases exhibit diverse structural mechanisms of regulation and have been fascinating subjects for structural biologists from the first crystal structure of a protein kinase over 30 years ago, to recent insights into kinase assemblies enabled by the breakthroughs in cryo-EM. Protein kinases are high-priority targets for drug discovery in oncology and other disease settings, and kinase inhibitors have transformed the outcomes of specific groups of patients. Most kinase inhibitors are ATP competitive, deriving potency by occupying the deep hydrophobic pocket at the heart of the kinase domain. Selectivity of inhibitors depends on exploiting differences between the amino acids that line the ATP site and exploring the surrounding pockets that are present in inactive states of the kinase. More recently, allosteric pockets outside the ATP site are being targeted to achieve high selectivity and to overcome resistance to current therapeutics. Here, we review the key regulatory features of the protein kinase family, describe the different types of kinase inhibitors, and highlight examples where the understanding of kinase regulatory mechanisms has gone hand in hand with the development of inhibitors.

Molecular Insights into the Regulation of 3-Phosphoinositide-Dependent Protein Kinase 1: Modeling the Interaction between the Kinase and the Pleckstrin Homology Domains

The 3-phosphoinositide-dependent protein kinase 1 (PDK1) K465E mutant kinase can still activate protein kinase B (PKB) at the membrane in a phosphatidylinositol-3,4,5-trisphosphate (PIP₃, PtdIns(3,4,5)P₃) independent manner. To understand this new PDK1 regulatory mechanism, docking and molecular dynamics calculations were performed for the first time to simulate the wild-type kinase domain-pleckstrin homology (PH) domain complex with PH-in and PH-out conformations. These simulations were then compared to the PH-in model of the KD-PH(mutant K465E) PDK1 complex. Additionally, three KD-PH complexes were simulated, including a substrate analogue bound to a hydrophobic pocket (denominated the PIF-pocket) substrate-docking site. We find that only the PH-out conformation, with the PH domain well-oriented to interact with the cellular membrane, is active for wild-type PDK1. In contrast, the active conformation of the PDK1 K465E mutant is PH-in, being ATP-stable at the active site while the PIF-pocket is more accessible to the peptide substrate. We corroborate that both the docking-site binding and the catalytic activity are in fact enhanced in knock-in mouse samples expressing the PDK1 K465E protein, enabling the phosphorylation of PKB in the absence of PIP₃ binding.

Precision Medicine Highlights Dysregulation of the CDK4/6 Cell Cycle Regulatory Pathway in Pediatric, Adolescents and Young Adult Sarcomas

Simple Summary

This review provides an overview of clinical features and current therapies in children, adolescents, and young adults (AYA) with sarcoma. It highlights the basic and clinical findings on the cyclin-dependent kinases 4 and 6 (CDK4/6) cell cycle regulatory pathway in the context of the precision medicine-based molecular profiles of the three most common types of pediatric and AYA sarcomas—osteosarcoma (OS), rhabdomyosarcoma (RMS), and Ewing sarcoma (EWS).

Abstract

Despite improved therapeutic and clinical outcomes for patients with localized diseases, outcomes for pediatric and AYA sarcoma patients with high-grade or aggressive disease are still relatively poor. With advancements in next generation sequencing (NGS), precision medicine now provides a strategy to improve outcomes in patients with aggressive disease by identifying biomarkers of therapeutic sensitivity or resistance. The integration of NGS into clinical decision making not only increases the accuracy of diagnosis and prognosis, but also has the potential to identify effective and less toxic therapies for pediatric and AYA sarcomas. Genome and transcriptome profiling have detected dysregulation of the CDK4/6 cell cycle regulatory pathway in subpopulations of pediatric and AYA OS, RMS, and EWS. In these patients, the inhibition of CDK4/6 represents a promising precision medicine-guided therapy. There is a critical need, however, to identify novel and promising combination therapies to fight the development of resistance to CDK4/6 inhibition. In this review, we offer rationale and perspective on the promise and challenges of this therapeutic approach.

A Genome-Wide Screen Identifies PDPK1 as a Target to Enhance the Efficacy of MEK1/2 Inhibitors in NRAS Mutant Melanoma

Melanomas frequently harbor activating NRAS mutations. However, limited advance has been made in developing targeted therapy options for patients with NRAS mutant melanoma. MEK inhibitors (MEKi) show modest efficacy in the clinic and their actions need to be optimized. In this study, we performed a genome-wide CRISPR-Cas9-based screen and demonstrated that loss of phosphoinositide-dependent kinase-1 (PDPK1) enhances the efficacy of MEKi. The synergistic effects of PDPK1 loss and MEKi was validated in NRAS mutant melanoma cell lines using pharmacologic and molecular approaches. Combined PDPK1 inhibitors (PDPK1i) with MEKi suppressed NRAS mutant xenograft growth and induced gasdermin E-associated pyroptosis. In an immune-competent allograft model, PDPK1i+MEKi increased the ratio of intratumoral CD8+ T cells, delayed tumor growth, and prolonged survival; the combination treatment was less effective against tumors in immune-deficient mice. These data suggest PDPK1i+MEKi as an efficient immunostimulatory strategy against NRAS mutant melanoma.

SIGNIFICANCE

Targeting PDPK1 stimulates antitumor immunity and sensitizes NRAS mutant melanoma to MEK inhibition, providing rationale for the clinical development of a combinatorial approach for treating patients with melanoma.

Prediction of Protein Allosteric Signalling Pathways and Functional Residues Through Paths of Optimised Propensity

Allostery commonly refers to the mechanism that regulates protein activity through the binding of a molecule at a different, usually distal, site from the orthosteric site. The omnipresence of allosteric regulation in nature and its potential for drug design and screening render the study of allostery invaluable. Nevertheless, challenges remain as few computational methods are available to effectively predict allosteric sites, identify signalling pathways involved in allostery, or to aid with the design of suitable molecules targeting such sites. Recently, bond-to-bond propensity analysis has been shown successful at identifying allosteric sites for a large and diverse group of proteins from knowledge of the orthosteric sites and its ligands alone by using network analysis applied to energy-weighted atomistic protein graphs. To address the identification of signalling pathways, we propose here a method to compute and score paths of optimised propensity that link the orthosteric site with the identified allosteric sites, and identifies crucial residues that contribute to those paths. We showcase the approach with three well-studied allosteric proteins: h-Ras, caspase-1, and 3-phosphoinositide-dependent kinase-1 (PDK1). Key residues in both orthosteric and allosteric sites were identified and showed agreement with experimental results, and pivotal signalling residues along the pathway were also revealed, thus providing alternative targets for drug design. By using the computed path scores, we were also able to differentiate the activity of different allosteric modulators.

The overview of Mitogen-activated extracellular signal-regulated kinase (MEK)-based dual inhibitor in the treatment of cancers

Mitogen-activated extracellular signal-regulated kinase 1 and 2 (MEK1/2) are the critical components of the mitogen-activated protein kinase/extracellular signal-regulated kinase 1 and 2 (MAPK/ERK1/2) signaling pathway which is one of the well-characterized kinase cascades regulating cell proliferation, differentiation, growth, metabolism, survival and mobility both in normal and cancer cells. The aberrant activation of MAPK/ERK1/2 pathway is a hallmark of numerous human cancers, therefore targeting the components of this pathway to inhibit its dysregulation is a promising strategy for cancer treatment. Enormous efforts have been done in the development of MEK1/2 inhibitors and encouraging advancements have been made, including four inhibitors approved for clinical use. However, due to the multifactorial property of cancer and rapidly arising drug resistance, the clinical efficacy of these MEK1/2 inhibitors as monotherapy are far from ideal. Several alternative strategies have been developed to improve the limited clinical efficacy, including the dual inhibitor which is a single drug molecule able to simultaneously inhibit two targets. In this review, we first introduced the activation and function of the MAPK/ERK1/2 components and discussed the advantages of MEK1/2-based dual inhibitors compared with the single inhibitors and combination therapy in the treatment of cancers. Then, we overviewed the MEK1/2-based dual inhibitors for the treatment of cancers and highlighted the theoretical basis of concurrent inhibition of MEK1/2 and other targets for development of these dual inhibitors. Besides, the status and results of these dual inhibitors in both preclinical and clinical studies were also the focus of this review.

Idelalisib activates AKT via increased recruitment of PI3Kδ/PI3Kβ to BCR signalosome while reducing PDK1 in post-therapy CLL cells

Idelalisib targets PI3Kδ in the BCR pathway generating only a partial response in CLL patients, indicating that the leukemic cells may have evolved escape signals. Indeed, we detected increased activation of AKT accompanied by upregulation of MYC/BCL2 in post-therapy CLL cells from patients treated with idelalisib/ofatumumab. To unravel the mechanism of increased AKT-activation, we studied the impact of idelalisib on a CLL-derived cell line, MEC1, as a model. After an initial inhibition, AKT-activation level was restored in idelalisib-treated MEC1 cells in a time-dependent manner. As BCAP (B-cell adaptor for PI3K) and CD19 recruit PI3Kδ to activate AKT upon BCR-stimulation, we examined if idelalisib-treatment altered PI3Kδ-recruitment. Immunoprecipitation of BCAP/CD19 from idelalisib-treated MEC1 cells showed increased recruitment of PI3Kδ in association with PI3Kβ, but not PI3Kα or PI3Kγ and that, targeting both PI3Kδ with PI3Kβ inhibited AKT-reactivation. We detected similar, patient-specific recruitment pattern of PI3K-isoforms by BCAP/CD19 in post-idelalisib CLL cells with increased AKT-activation. Interestingly, a stronger inhibitory effect of idelalisib on P-AKT (T308) than S473 was discernible in idelalisib-treated cells despite increased recruitment of PI3Kδ/PI3Kβ and accumulation of phosphatidylinositol-3,4,5-triphosphate; which could be attributed to reduced PDK1 activity. Thus, administration of isoform-specific inhibitors may prove more effective strategy for treating CLL patients.

Inhibition of PDK1 enhances radiosensitivity and reverses epithelial-mesenchymal transition in nasopharyngeal carcinoma

BACKGROUND

Radioresistance challenges the clinical outcomes of nasopharyngeal carcinoma (NPC). The 3-phosphoinositide-dependent protein kinase 1 (PDK1) is a crucial kinase of PI3K/AKT signaling pathway which has been implicated in the process of radioresistance. However, the role of PDK1 in NPC remains largely unclear.

METHODS

The expression of PDK1 was determined by immunohistochemistry and Western blot. The effects of RNA interference and pharmacologic inhibitor of PDK1 in combination with irradiation were investigated.

RESULTS

Overexpression of PDK1 was correlated with poor prognosis in patients with NPC. PDK1 depletion enhanced radiosensitivity of NPC cells both in vitro and in vivo. Additionally, a specific PDK1 inhibitor also had the potential to enhance radiosensitivity in radioresistant NPC cells. Mechanistically, PDK1 depletion inhibited various targets of AKT including mTOR and GSK-3β and reversed the epithelial-mesenchymal transition.

CONCLUSIONS

These findings indicated that PDK1 might be a potential target for NPC.

MicroRNAs as the critical regulators of cell migration and invasion in thyroid cancer

Thyroid cancer (TC) is one of the most frequent endocrine malignancies that is more common among females. Tumor recurrence is one of the most important clinical manifestations in differentiated TC which is associated with different factors including age, tumor size, and histological features. Various molecular processes such as genetic or epigenetic modifications and non-coding RNAs are also involved in TC progression and metastasis. The epithelial-to-mesenchymal transition (EMT) is an important biological process during tumor invasion and migration that affects the initiation and transformation of early-stage tumors into invasive malignancies. A combination of transcription factors, growth factors, signaling pathways, and epigenetic regulations affect the thyroid cell migration and EMT process. MicroRNAs (miRNAs) are important molecular factors involved in tumor metastasis by regulation of EMT-activating signaling pathways. Various miRNAs are involved in the signaling pathways associated with TC metastasis which can be used as diagnostic and therapeutic biomarkers. Since, the miRNAs are sensitive, specific, and non-invasive, they can be suggested as efficient and optimal biomarkers of tumor invasion and metastasis. In the present review, we have summarized all of the miRNAs which have been significantly involved in thyroid tumor cells migration and invasion. We also categorized all of the reported miRNAs based on their cellular processes to clarify the molecular role of miRNAs during thyroid tumor cell migration and invasion. This review paves the way of introducing a non-invasive diagnostic and prognostic panel of miRNAs in aggressive and metastatic TC patients.

Drosophila melanogaster as a low-cost and valuable model for studying type 2 diabetes

Drosophila melanogaster has been used as the most successful invertebrate model for studying metabolic diseases such as type 2 diabetes (T2D). We induced T2D by feeding Drosophila larvae on a high-sugar diet (HSD). The glucose and trehalose, glycogen, lipid, triglyceride, and protein levels were determined in HSD-fed larvae. Moreover, larval food intake, water content, size, and weight in addition to the development until pupation were observed. Levels of Drosophila insulin-like peptides (DILPs 2, 3, and 5), as well as adipokinetic hormone (AKH), were also determined in HSD-fed larvae by quantitative real-time polymerase chain reaction. The results demonstrated that HSD could induce elevated levels of glucose, trehalose, glycogen, and proteins in larvae. The larvae consumed less food intake and were smaller, lighter, and less developed on HSD than those on the control diet. Moreover, the water content of larvae fed HSD was similar to that fed the control diet. HSD induced higher expression of DILP3 and AKH, confirming hyperglycemia with insulin resistance. In sum, Drosophila offers an appropriate model for quick and inexpensive in vivo experimentation on human metabolic diseases.

The non-canonical nuclear functions of key players of the PI3K-AKT-MTOR pathway

The PI3K-AKT-MTOR signal transduction pathway is one of the essential signalling cascades within the cell due to its involvement in many vital functions. The pathway initiates with the recruitment of phosphatidylinositol-3 kinases (PI3Ks) onto the plasma membrane, generating phosphatidylinositol-3,4,5-triphosphate [PtdIns(3,4,5)P₃ ] and subsequently activating AKT. Being the central node of the PI3K network, AKT activates the mechanistic target of rapamycin kinase complex 1 (MTORC1) via Tuberous sclerosis complex 2 inhibition in the cytoplasm. Although the cytoplasmic role of the pathway has been widely explored for decades, we now know that most of the effector molecules of the PI3K axis diverge from the canonical route and translocate to other cell organelles including the nucleus. The presence of phosphoinositides (PtdIns) inside the nucleus itself indicates the existence of a nuclear PI3K signalling. The nuclear localization of these signaling components is evident in regulating many nuclear processes like DNA replication, transcription, DNA repair, maintenance of genomic integrity, chromatin architecture, and cell cycle control. Here, our review intends to present a comprehensive overview of the nuclear functions of the PI3K-AKT-MTOR signaling biomolecules.

Reducing PDK1/Akt Activity: An Effective Therapeutic Target in the Treatment of Alzheimer's Disease

Alzheimer’s disease (AD) is a common age-related neurodegenerative disease that leads to memory loss and cognitive function damage due to intracerebral neurofibrillary tangles (NFTs) and amyloid-β (Aβ) protein deposition. The phosphoinositide-dependent protein kinase (PDK1)/protein kinase B (Akt) signaling pathway plays a significant role in neuronal differentiation, synaptic plasticity, neuronal survival, and neurotransmission via the axon–dendrite axis. The phosphorylation of PDK1 and Akt rises in the brain, resulting in phosphorylation of the TNF-α-converting enzyme (TACE) at its cytoplasmic tail (the C-terminal end), changing its internalization as well as its trafficking. The current review aimed to explain the mechanisms of the PDK1/Akt/TACE signaling axis that exerts its modulatory effect on AD physiopathology. We provide an overview of the neuropathological features, genetics, Aβ aggregation, Tau protein hyperphosphorylation, neuroinflammation, and aging in the AD brain. Additionally, we summarized the phosphoinositide 3-kinase (PI3K)/PDK1/Akt pathway-related features and its molecular mechanism that is dependent on TACE in the pathogenesis of AD. This study reviewed the relationship between the PDK1/Akt signaling pathway and AD, and discussed the role of PDK1/Akt in resisting neuronal toxicity by suppressing TACE expression in the cell membrane. This work also provides a perspective for developing new therapeutics targeting PDK1/Akt and TACE for the treatment of AD.

Screening the Toxoplasma kinome with high-throughput tagging identifies a regulator of invasion and egress

Protein kinases regulate fundamental aspects of eukaryotic cell biology, making them attractive chemotherapeutic targets in parasites like Plasmodium spp. and Toxoplasma gondii. To systematically examine the parasite kinome, we developed a high-throughput tagging (HiT) strategy to endogenously label protein kinases with an auxin-inducible degron and fluorophore. Hundreds of tagging vectors were assembled from synthetic sequences in a single reaction and used to generate pools of mutants to determine localization and function. Examining 1,160 arrayed clones, we assigned 40 protein localizations and associated 15 kinases with distinct defects. The fitness of tagged alleles was also measured by pooled screening, distinguishing delayed from acute phenotypes. A previously unstudied kinase, associated with delayed loss, was shown to be a regulator of invasion and egress. We named the kinase Store Potentiating/Activating Regulatory Kinase (SPARK), based on its impact on intracellular Ca²⁺ stores. Despite homology to mammalian PDK1, SPARK lacks a lipid-binding domain, suggesting a rewiring of the pathway in parasites. HiT screening extends genome-wide approaches into complex cellular phenotypes, providing a scalable and versatile platform to dissect parasite biology.

Ontogeny and Vulnerabilities of Drug-Tolerant Persisters in HER2+ Breast Cancer

Resistance to targeted therapies is an important clinical problem in HER2-positive (HER2+) breast cancer. "Drug-tolerant persisters" (DTP), a subpopulation of cancer cells that survive via reversible, nongenetic mechanisms, are implicated in resistance to tyrosine kinase inhibitors (TKI) in other malignancies, but DTPs following HER2 TKI exposure have not been well characterized. We found that HER2 TKIs evoke DTPs with a luminal-like or a mesenchymal-like transcriptome. Lentiviral barcoding/single-cell RNA sequencing reveals that HER2+ breast cancer cells cycle stochastically through a "pre-DTP" state, characterized by a G0-like expression signature and enriched for diapause and/or senescence genes. Trajectory analysis/cell sorting shows that pre-DTPs preferentially yield DTPs upon HER2 TKI exposure. Cells with similar transcriptomes are present in HER2+ breast tumors and are associated with poor TKI response. Finally, biochemical experiments indicate that luminal-like DTPs survive via estrogen receptor-dependent induction of SGK3, leading to rewiring of the PI3K/AKT/mTORC1 pathway to enable AKT-independent mTORC1 activation.

SIGNIFICANCE

DTPs are implicated in resistance to anticancer therapies, but their ontogeny and vulnerabilities remain unclear. We find that HER2 TKI-DTPs emerge from stochastically arising primed cells ("pre-DTPs") that engage either of two distinct transcriptional programs upon TKI exposure. Our results provide new insights into DTP ontogeny and potential therapeutic vulnerabilities. This article is highlighted in the In This Issue feature, p. 873.

S6K1-mediated phosphorylation of PDK1 impairs AKT kinase activity and oncogenic functions

Functioning as a master kinase, 3-phosphoinositide-dependent protein kinase 1 (PDK1) plays a fundamental role in phosphorylating and activating protein kinases A, B and C (AGC) family kinases, including AKT. However, upstream regulation of PDK1 remains largely elusive. Here we report that ribosomal protein S6 kinase beta 1 (S6K1), a member of AGC kinases and downstream target of mechanistic target of rapamycin complex 1 (mTORC1), directly phosphorylates PDK1 at its pleckstrin homology (PH) domain, and impairs PDK1 interaction with and activation of AKT. Mechanistically, S6K1-mediated phosphorylation of PDK1 augments its interaction with 14-3-3 adaptor protein and homo-dimerization, subsequently dissociating PDK1 from phosphatidylinositol 3,4,5 triphosphate (PIP₃) and retarding its interaction with AKT. Pathologically, tumor patient-associated PDK1 mutations, either attenuating S6K1-mediated PDK1 phosphorylation or impairing PDK1 interaction with 14-3-3, result in elevated AKT kinase activity and oncogenic functions. Taken together, our findings not only unravel a delicate feedback regulation of AKT signaling via S6K1-mediated PDK1 phosphorylation, but also highlight the potential strategy to combat mutant PDK1-driven cancers.

The direct upstream regulation of PDK1 is not fully understood. Here the authors demonstrate that S6K1 directly phosphorylates PDK1 to inhibit AKT kinase activity and its ability to drive tumourigenesis.

PIK3CA Mutations Drive Therapeutic Resistance in Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer

The phosphatidylinositol 3-kinase (PI3K) pathway is an intracellular pathway activated in response to progrowth signaling, such as human epidermal growth factor receptor 2 (HER2) and other kinases. Abnormal activation of PI3K has long been recognized as one of the main oncogenic drivers in breast cancer, including HER2-positive (HER2+) subtype. Somatic activating mutations in the gene encoding PI3K alpha catalytic subunit (PIK3CA) are present in approximately 30% of early-stage HER2+ tumors and drive therapeutic resistance to multiple HER2-targeted agents. Here, we review currently available agents targeting PI3K, discuss their potential role in HER2+ breast cancer, and provide an overview of ongoing trials of PI3K inhibitors in HER2+ disease. Additionally, we review the landscape of PIK3CA mutational testing and highlight the gaps in knowledge that could present potential barriers in the effective application of PI3K inhibitors for treatment of HER2+ breast cancer.