A Non-canonical PDK1-RSK Signal Diminishes Pro-caspase-8-Mediated Necroptosis Blockade.

Necroptosis induction in vitro often requires caspase-8 (Casp8) inhibition by zVAD because pro-Casp8 cleaves RIP1 to disintegrate the necrosome. It has been unclear how the Casp8 blockade of necroptosis is eliminated naturally. Here, we show that pro-Casp8 within the necrosome can be inactivated by phosphorylation at Thr265 (pC8T265). pC8T265 occurs in vitro in various necroptotic cells and in the cecum of TNF-treated mice. p90 RSK is the kinase of pro-Casp8. It is activated by a mechanism that does not need ERK but PDK1, which is recruited to the RIP1-RIP3-MLKL-containing necrosome. Phosphorylation of pro-Casp8 at Thr265 can substitute for zVAD to permit necroptosis in vitro. pC8T265 mimic T265E knockin mice are embryonic lethal due to unconstrained necroptosis, and the pharmaceutical inhibition of RSK-mediated pC8T265 diminishes TNF-induced cecum damage and lethality in mice by halting necroptosis. Thus, phosphorylation of pro-Casp8 at Thr265 by RSK is an intrinsic mechanism for passing the Casp8 checkpoint of necroptosis.

Histone H3Y99sulf regulates hepatocellular carcinoma responding to hypoxia.

Histone H3 tyrosine-99 sulfation (H3Y99sulf) is a recently identified histone mark that can cross-talk with H4R3me2a to regulate gene transcription, but its role in cancer biology is less studied. Here, we report that H3Y99sulf is a cancer-associated histone mark that can mediate hepatocellular carcinoma (HCC) cells responding to hypoxia. Hypoxia-stimulated SNAIL pathway elevates the expression of PAPSS2, which serves as a source of adenosine 3'-phosphate 5'-phos-phosulfate for histone sulfation and results in upregulation of H3Y99sulf. The transcription factor TDRD3 is the downstream effector of H3Y99sulf-H4R3me2a axis in HCC. It reads and co-localizes with the H3Y99sulf-H4R3me2a dual mark in the promoter regions of HIF1A and PDK1 to regulate gene transcription. Depletion of SULT1B1 can effectively reduce the occurrence of H3Y99sulf-H4R3me2a-TDRD3 axis in gene promoter regions and lead to downregulation of targeted gene transcription. Hypoxia-inducible factor 1-alpha and PDK1 are master regulators for hypoxic responses and cancer metabolism. Disruption of the H3Y99sulf-H4R3me2a-TDRD3 axis can inhibit the expression and functions of hypoxia-inducible factor 1-alpha and PDK1, resulting in suppressed proliferation, tumor growth, and survival of HCC cells suffering hypoxia stress. The present study extends the regulatory and functional mechanisms of H3Y99sulf and improves our understanding of its role in cancer biology.

Molecular insights into the regulatory landscape of PKC-related kinase-2 (PRK2/PKN2) using targeted small compounds.

The PKC-related kinases (PRKs, also termed PKNs) are important in cell migration, cancer, hepatitis C infection, and nutrient sensing. They belong to a group of protein kinases called AGC kinases that share common features like a C-terminal extension to the catalytic domain comprising a hydrophobic motif. PRKs are regulated by N-terminal domains, a pseudosubstrate sequence, Rho-binding domains, and a C2 domain involved in inhibition and dimerization, while Rho and lipids are activators. We investigated the allosteric regulation of PRK2 and its interaction with its upstream kinase PDK1 using a chemical biology approach. We confirmed the phosphoinositide-dependent protein kinase 1 (PDK1)-interacting fragment (PIF)-mediated docking interaction of PRK2 with PDK1 and showed that this interaction can be modulated allosterically. We showed that the polypeptide PIFtide and a small compound binding to the PIF-pocket of PRK2 were allosteric activators, by displacing the pseudosubstrate PKL region from the active site. In addition, a small compound binding to the PIF-pocket allosterically inhibited the catalytic activity of PRK2. Together, we confirmed the docking interaction and allostery between PRK2 and PDK1 and described an allosteric communication between the PIF-pocket and the active site of PRK2, both modulating the conformation of the ATP-binding site and the pseudosubstrate PKL-binding site. Our study highlights the allosteric modulation of the activity and the conformation of PRK2 in addition to the existence of at least two different complexes between PRK2 and its upstream kinase PDK1. Finally, the study highlights the potential for developing allosteric drugs to modulate PRK2 kinase conformations and catalytic activity.

An indel introduced by Neanderthal introgression, rs3835124:ATTTATT > ATT, might contribute to prostate cancer risk by regulating PDK1 expression.

INTRODUCTION: Prostate cancer is one of the most common cancer types in males and rs12621278:A > G has been suggested to be associated with this disease by previous genome-wide association studies. One thousand genomes project data analysis indicated that rs12621278:A > G is within two long-core haplotypes. However, the origin, causal variant(s), and molecular function of these haplotypes were remaining unclear. MATERIALS AND METHODS: Population genetics analysis and functional genomics work was performed for this locus. RESULTS: Phylogeny analysis verified that the rare haplotype is derived from Neanderthal introgression. Genome annotation suggested that three genetic variants in the core haplotypes, rs116108611:G > A, rs139972066:AAAAAAAA > AAAAAAAAA, and rs3835124:ATTTATT > ATT, are located in functional regions. Luciferase assay indicated that rs139972066:AAAAAAAA > AAAAAAAAA and rs116108611:G > A are not able to alter ITGA6 (integrin alpha 6) and ITGA6 antisense RNA 1 expression, respectively. In contrast, rs3835124:ATTTATT > ATT can significantly influence PDK1 (pyruvate dehydrogenase kinase 1) expression, which was verified by expression quantitative trait locus analysis. This genetic variant can alter transcription factor cut like homeobox 1 interaction efficiency. The introgressed haplotype was observed to be subject to positive selection in East Asian populations. The molecular function of the haplotype suggested that Neanderthal should be with lower PDK1 expression and further different energy homeostasis from modern human. CONCLUSION: This study provided new insight into the contribution of Neanderthal introgression to human phenotypes.

The effect of PDK1 in maintaining immune cell development and function.

3-phosphoinositide-dependent protein kinase 1 (PDK1) exhibits a substantial influence on immune cell development by establishing a vital connection between PI3K and downstream mTOR signaling cascades. However, it remains unclear whether PDK1 signaling affects the homeostasis and functionality of immune cells. To explore the impact of PDK1 on different immune cells within immune organs, transgenic mouse strains with lymphocyte-specific PDK1 knockout (PDK1fl/fl CD2-Cre) were generated. Unlike wild-type (WT) mice, lymphocyte-specific PDK1 knockout (KO) mice exhibited thymic atrophy, elevated percentages of CD8+ T cells and neutrophils, and reduced proportions of γδ T cells, B cells, and NK cells in the spleen. Functional analysis revealed elevated release of IFN-γ and IL-17A by T cells in PDK1 KO mice, contrasting with diminished levels observed in γδ T cells and Treg cells. Furthermore, the activation, cytotoxicity, and migratory potential of γδ T cells in PDK1 KO mice are heightened, indicating a potential association with the regulation of the mTOR signaling pathway. To conclude, the findings of this research demonstrated that specific knockout of PDK1 in lymphocytes hindered T cell development in the thymus and exhibited a substantial influence on immune cell homeostasis in the spleen and lymph nodes.

Circ_0001944 depletion inhibits glycolysis and esophageal cancer progression by binding to miR-338-5p to reduce PDK1 expression.

Circular RNA (circRNA) plays multiple roles in the development of esophageal cancer (EC). Herein, we investigate the function of circ_0001944 in EC progression and the related mechanism. Expression of circ_0001944, microRNA-338-5p (miR-338-5p), pyruvate dehydrogenase kinase 1 (PDK1), E-cadherin and N-cadherin was analyzed by quantitative real-time polymerase chain reaction, Western blotting or immunohistochemistry assay. Cell viability, proliferation, apoptosis, invasion and migration were investigated by cell counting kit-8 (CCK-8), 5-Ethynyl-2'-deoxyuridine (EdU), flow cytometry, transwell invasion and wound-healing assays, respectively. Glucose consumption was detected by Glucose Assay Kit. Lactate production was analyzed by Lactate Assay Kit. ATP/ADP ratio was determined by ADP/ATP ratio Assay Kit. The associations among circ_0001944, miR-338-5p and PDK1 were identified by dual-luciferase reporter and RNA pull-down assays. Xenograft mouse model assay was used to explore the role of circ_0001944 on tumor tumorigenesis in vivo. Circ_0001944 and PDK1 expression were significantly upregulated, while miR-338-5p was downregulated in EC tissues and cells in contrast with normal esophageal tissues and cells. Circ_0001944 knockdown inhibited EC cell proliferation, invasion, migration and glycolysis but induced apoptosis. Meanwhile, circ_0001944 depletion suppressed tumor tumorigenesis in vivo. Mechanistically, circ_0001944 bound to miR-338-5p, and miR-338-5p targeted PDK1. In addition, miR-338-5p inhibitors attenuated circ_0001944 depletion-induced effects in EC cells. The regulation of miR-338-5p on EC progression involved the downregulation of PDK1. Further, circ_0001944 controlled PDK1 expression through miR-338-5p. Circ_0001944 knockdown inhibited EC development and glycolysis by regulating the miR-338-5p/PDK1 pathway, providing a promising target for EC therapy.

Circ_0002395 promotes aerobic glycolysis and proliferation in pancreatic adenocarcinoma cells via miR-548c-3p/PDK1 axis.

Circular RNAs (circRNAs) showing unusual expressions have been discovered in pancreatic adenocarcinoma (PAAD). However, the functions and underlying mechanisms of these circRNAs still remain largely unclear. Our current study discovered a notable increase in the expression of circRNA hsa_circ_0002395 (circ_0002395) in both PAAD tissues and cell lines. This up-regulation of circ_0002395 was found to be associated with larger tumor sizes and lymph node metastasis. Furthermore, our findings showed that circ_0002395 facilitated aerobic glycolysis and cell proliferation in PAAD cells by regulating the miR-548c-3p/PDK1 axis. Mechanistically, we identified circ_0002395 as a competing endogenous RNA (ceRNA) that sponged miR-548c-3p, thereby promoting PDK1 expression and aerobic glycolysis, and ultimately resulting in the enhancement of cell proliferation. Our findings found that circ_0002395 promoted proliferation of PAAD cells by enhancing PDK1 expression and aerobic glycolysis by sponging miR-548c-3p.

Deficiency of Pdk1 drives heart failure by impairing taurine homeostasis through Slc6a6.

3-Phosphoinositide-dependent protein kinase-1 (Pdk1) as a serine/threonine protein kinase plays a critical role in multiple signaling pathways. Analysis of the gene expression omnibus database showed that Pdk1 was significantly downregulated in patients with heart diseases. Gene set enrichment analysis of the proteomics dataset identified apoptotic- and metabolism-related signaling pathways directly targeted by Pdk1. Previously, our research indicated that Pdk1 deletion-induced metabolic changes might be involved in the pathogenesis of heart failure; however, the underlying mechanism remains elusive. Here, we demonstrated that deficiency of Pdk1 resulted in apoptosis, oxidative damage, and disturbed metabolism, both in vivo and in vitro. Furthermore, profiling of metabonomics by 1 H-NMR demonstrated that taurine was the major differential metabolite in the heart of Pdk1-knockout mice. Taurine treatment significantly reduced the reactive oxygen species production and apoptosis, improved cardiac function, and prolonged the survival time in Pdk1 deficient mice. Proteomic screening identified solute carrier family 6 member 6 (Slc6a6) as the downstream that altered taurine levels in Pdk1-expression cells. Consistently, cellular apoptosis and oxidative damage were rescued by Slc6a6 in abnormal Pdk1 expression cells. These findings collectively suggest that Pdk1 deficiency induces heart failure via disturbances in taurine homeostasis, triggered by Slc6a6.

Inhibition of the ubiquitin-proteasome system reduces the abundance of pyruvate dehydrogenase kinase 1 in cultured myotubes.

Pyruvate dehydrogenase kinase (PDK), which phosphorylates the pyruvate dehydrogenase complex, regulates glucose metabolism in skeletal muscle. PDK1, an isozyme whose expression is controlled by hypoxia-inducible factor-1α (HIF-1α), is thought to play a role in muscle adaptation to hypoxia. While transcriptional upregulation of PDK1 by HIF-1α is well characterised, mechanisms controlling proteolysis of PDK1 in skeletal muscle have not been thoroughly investigated. Proteasome inhibitor MG132 paradoxically reduced the abundance of PDK1 in human cancer cells and rat L6 myotubes, suggesting that MG132 might direct PDK1 towards autophagic degradation. The objectives of our current study were to determine (1) whether MG132 suppresses PDK1 levels in primary human myotubes, (2) whether chloroquine, an inhibitor of autophagy, prevents MG132-induced suppression of PDK1 in L6 myotubes, and (3) whether PYR-41, an inhibitor of ubiquitination, suppresses PDK1 in L6 myotubes. Using qPCR and/or immunoblotting, we found that despite markedly upregulating HIF-1α protein, MG132 did not alter the PDK1 expression in cultured primary human myotubes, while it suppressed both PDK1 mRNA and protein in L6 myotubes. The PDK1 levels in L6 myotubes were suppressed also during co-treatment with chloroquine and MG132. PYR-41 markedly increased the abundance of HIF-1α in primary human and L6 myotubes, while reducing the abundance of PDK1. In L6 myotubes treated with PYR-41, chloroquine increased the abundance of the epidermal growth factor receptor, but did not prevent the suppression of PDK1. Collectively, our results suggest that cultured myotubes degrade PDK1 via a pathway that cannot be inhibited by MG132, PYR-41, and/or chloroquine.

KLK10 promotes the progression of KRAS mutant colorectal cancer via PAR1-PDK1-AKT signaling pathway.

Kirsten rat sarcoma virus (KRAS) gene mutation is common in colorectal cancer (CRC) and is often predictive of treatment failure and poor prognosis. To understand the mechanism, we compared the transcriptome of CRC patients with wild-type and mutant KRAS and found that KRAS mutation is associated with the overexpression of a secreted serine protease, kallikrein-related peptidase 10 (KLK10). Moreover, using in vitro and in vivo models, we found that KLK10 overexpression favors the rapid growth and liver metastasis of KRAS mutant CRC and can also impair the efficacy of KRAS inhibitors, leading to drug resistance and poor survival. Further functional assays revealed that the oncogenic role of KLK10 is mediated by protease-activated receptor 1 (PAR1). KLK10 cleaves and activates PAR1, which further activates 3-phosphoinositide-dependent kinase 1 (PDK1)-AKT oncogenic pathway. Notably, suppressing PAR1-PDK1-AKT cascade via KLK10 knockdown can effectively inhibit CRC progression and improve the sensitivity to KRAS inhibitor, providing a promising therapeutic strategy. Taken together, our study showed that KLK10 promotes the progression of KRAS mutant CRC via activating PAR1-PDK1-AKT signaling pathway. These findings expanded our knowledge of CRC development, especially in the setting of KRAS mutation, and also provided novel targets for clinical intervention.

Combined inhibition of pyruvate dehydrogenase kinase 1 and hexokinase 2 induces apoptsis in non-small cell lung cancer cell models.

Many cancer cells exhibit enhanced glycolysis, which is seen as one of the hallmark metabolic alterations, known as Warburg effect. Substantial evidence shows that upregulated glycolytic enzymes are often linked to malignant growth. Using glycolytic inhibitors for anticancer treatment has become appealing in recent years for therapeutic intervention in cancers with highly glycolytic characteristic, including non-small cell lung cancer (NSCLC). In this work, we studied the anticancer effects and the underlying mechanisms of combination of benzerazide hydrocholoride (Benz), a hexokinase 2 (HK2) inhibitor and 64, a pyruvate dehydrogenase kinase 1 (PDK1) inhibitor, in several NSCLC cell lines. We found that combination of Benz and 64 exhibited strong synergistic anticancer effects in NCI-H1975, HCC827, NCI-H1299 and SK-LU-1 cell lines. With this combination treatment, we observed changes of certain mechanistic determinants associated with metabolic stress caused by glycolysis restriction, such as mitochondrial membrane potential depolarization, overproduction of reactive oxygen species [1], activation of AMPK and down-regulation of mTOR, which contributed to enhanced apoptosis. Moreover, Benz and 64 together significantly suppressed the tumor growth in HCC827 cell mouse xenograft model. Taken together, our study may suggest that combined inhibition of HK2 and PDK1 using Benz and 64 could be a viable anticancer strategy for NSCLC.

RP11-495P10.1 promotes HCC cell proliferation by regulating reprogramming of glucose metabolism and acetylation of the NR4A3 promoter via the PDK1/PDH axis.

The incidence and related death of hepatocellular carcinoma (HCC) have increased over the past decades. However, the molecular mechanisms underlying HCC pathogenesis are not fully understood. Long noncoding RNA (lncRNA) RP11-495P10.1 has been proven to be closely associated with the progression of prostate cancer, but its role and specific mechanism in HCC are still unknown. Here, we identify that RP11-495P10.1 is highly expressed in HCC tissues and cells and contributes to the proliferation of HCC cells. Moreover, this study demonstrates that RP11-495P10.1 affects the proliferation of HCC by negatively regulating the expression of nuclear receptor subfamily 4 group a member 3 (NR4A3). Glycometabolism reprogramming is one of the main characteristics of tumor cells. In this study, we discover that RP11-495P10.1 regulates glycometabolism reprogramming by changing the expression of pyruvate dehydrogenase kinase 1 (PDK1) and pyruvate dehydrogenase (PDH), thus contributing to the proliferation of HCC cells. Furthermore, knockdown of RP11-495P10.1 increases enrichment of H3K27Ac in the promoter of NR4A3 by promoting the activity of PDH and the production of acetyl-CoA, which leads to the increased transcription of NR4A3. Altogether, RP11-495P10.1 promotes HCC cell proliferation by regulating the reprogramming of glucose metabolism and acetylation of the NR4A3 promoter via the PDK1/PDH axis, which provides an lncRNA-oriented therapeutic strategy for the diagnosis and treatment of HCC.

Protective effects of activated vitamin D receptor on radiation-induced intestinal injury.

Radiation-induced intestinal injury (RIII) is a common complication after radiation therapy in patients with pelvic, abdominal, or retroperitoneal tumours. Recently, in the model of DSS (Dextran Sulfate Sodium Salt) -induced intestinal inflammatory injury, it has been found in the study that transgenic mice expressing hVDR in IEC (Intestinal Epithelial Cell) manifest highly anti-injury properties in colitis, suggesting that activated VDR in the epithelial cells of intestine may inhibit colitis by protecting the mucosal epithelial barrier. In this study, we investigated the effect of the expression and regulation of VDR on the protection of RIII, and the radiosensitivity in vitro experiments, and explored the initial mechanism of VDR in regulating radiosensitivity of IEC. As a result, we found that the expression of VDR in intestinal tissues and cells in mice can be induced by ionizing radiation. VDR agonists are able to prolong the average survival time of mice after radiation and reduce the radiation-induced intestinal injury. For lack of vitamin D, the radiosensitivity of intestinal epithelial cells in mice increased, which can be reduced by VDR activation. Ensuing VDR activation, the radiation-induced intestinal stem cells damage is decreased, and the regeneration and differentiation of intestinal stem cells is promoted as well. Finally, on the basis of sequencing analysis, we validated and found that VDR may target the HIF/PDK1 pathway to mitigate RIII. We concluded that agonism or upregulation of VDR expression attenuates radiation-induced intestinal damage in mice and promotes the repair of epithelial damage in intestinal stem cells.

PI3K/AKT/mTOR signaling transduction pathway and targeted therapies in cancer.

The PI3K/AKT/mTOR (PAM) signaling pathway is a highly conserved signal transduction network in eukaryotic cells that promotes cell survival, cell growth, and cell cycle progression. Growth factor signalling to transcription factors in the PAM axis is highly regulated by multiple cross-interactions with several other signaling pathways, and dysregulation of signal transduction can predispose to cancer development. The PAM axis is the most frequently activated signaling pathway in human cancer and is often implicated in resistance to anticancer therapies. Dysfunction of components of this pathway such as hyperactivity of PI3K, loss of function of PTEN, and gain-of-function of AKT, are notorious drivers of treatment resistance and disease progression in cancer. In this review we highlight the major dysregulations in the PAM signaling pathway in cancer, and discuss the results of PI3K, AKT and mTOR inhibitors as monotherapy and in co-administation with other antineoplastic agents in clinical trials as a strategy for overcoming treatment resistance. Finally, the major mechanisms of resistance to PAM signaling targeted therapies, including PAM signaling in immunology and immunotherapies are also discussed.

PDK1-stabilized LncRNA SPRY4-IT1 promotes breast cancer progression via activating NF-κB signaling pathway.

Pyruvate dehydrogenase kinase 1 (PDK1) is a widely known glycolytic enzyme, and some evidence showed that PDK1 promoted breast cancer by multiple approaches. However, very few lncRNAs have been identified to be associated with PDK1 in breast cancer in previous research. In this study, we found that lncRNA sprouty4-intron transcript 1 (SPRY4-IT1) was regulated by PDK1 with correlation analysis, and PDK1 upregulated SPRY4-IT1 remarkably in breast cancer cells, as PDK1 interacted with SPRY4-IT1 in the nucleus and significantly enhanced the stability of SRPY4-IT1. Furthermore, SPRY4-IT1 was highly expressed in breast cancer, significantly promoted the proliferation and inhibited apoptosis of breast cancer cells. In terms of mechanism, SPRY4-IT1 inhibited the transcription of NFKBIA and the expression of IκBα, thus promoting the formation of p50/p65 complex and activating NF-κB signaling pathway, which facilitated survival of breast cancer cells. Therefore, our finding reveals that PDK1/SPRY4-IT1/NFKBIA axis plays a crucial role that promoting tumor progression, and SPRY4-IT1 knockdown incombined with PDK1 inhibitor is promising to be a new therapeutic strategy in breast cancer.

Aa-Z2 triggers ROS-induced apoptosis of osteosarcoma by targeting PDK-1.

BACKGROUND: Osteosarcoma (OS) is the most frequent cancer derived from bone, and the prognosis of OS is poor. Metabolic alterations have been previously reported to contribute to the development of OS, and arsenic compounds have been suggested to exhibit strong anti-OS effects. However, few studies have described the therapeutic efficiency of arsenic compounds by targeting metabolism in OS. METHODS: Here, we presented a novel organo-arsenic compound, Aa-Z2, and its antitumour efficacy against OS both in vitro and in vivo. RESULTS: Aa-Z2 induced OS cell apoptosis, G2/M phase arrest, and autophagy through the accumulation of reactive oxygen species (ROS). Elevated ROS functioned by promoting the mitochondrial-dependent caspase cascade and attenuating the PI3K/Akt/mTOR signalling pathway. N-acetylcysteine (NAC), a kind of ROS scavenger, could reverse the effects of Aa-Z2 treatment on 143B and HOS cells. Specifically, by targeting pyruvate dehydrogenase kinase 1 (PDK-1), Aa-Z2 induced changes in mitochondrial membrane potential and alterations in glucose metabolism to accumulate ROS. Overexpression of PDK-1 could partially desensitize OS cells to Aa-Z2 treatment. Importantly, Aa-Z2 suppressed tumour growth in our xenograft osteosarcoma model. CONCLUSION: The study provides new insights into the mechanism of Aa-Z2-related metabolic alterations in OS inhibition, as well as pharmacologic evidence supporting the development of metabolism-targeting therapeutics.

PDK1 upregulates PINK1-mediated pulmonary endothelial cell mitophagy during hypoxia-induced pulmonary vascular remodeling.

BACKGROUND: Hypoxic pulmonary hypertension (HPH) is a complication of lung diseases with pulmonary vascular remodeling, although the underlying molecular mechanisms have not been fully elucidated. This study investigated the underlying molecular events by using a rat HPH model and primary pulmonary microvascular endothelial cells (PMVECs). METHODS AND RESULTS: This study first established a rat HPH model and cultured PMVECs for transmission electron microscopic analysis and manipulation of 3-phosphoinositide-dependent protein kinase 1 (PDK1) or phosphatase and tensin homolog-induced kinase 1 (PINK1) expression in vitro. After that, the cell viability was assessed and the expression of different proteins was assayed using cell viability and western blot assays, respectively. Reactive oxygen species production, apoptosis, NLR family pyrin domain containing 3 (NLRP3) expression, and the levels of interleukin (IL)-1ß, IL-6, and IL-8 were also assessed, while the interaction of PDK1 and PINK1 was determined using co-immunoprecipitation/western blot assays. Hypoxia induced mitophagy in the PMVECs and upregulated PINK1/Parkin expression, whereas knockdown of PINK1 expression under hypoxic conditions inhibited cell proliferation but induced endothelial cell apoptosis in vitro, decreased reactive oxygen species production and NLRP3 expression, and reduced the levels of inflammatory factors in PMVECs. However, hypoxia induced PDK1 expression, whereas knockdown of PDK1 downregulated PINK1 expression. Furthermore, treatment of the model rats with the PDK1 inhibitor dichloroacetate (DCA) was able to decrease PINK1 expression. In addition, the PDK1 and PINK1 proteins could interact with each other in the mitochondria of PMVECs to regulate the cell viability. CONCLUSIONS: This study revealed that PDK1 induced PMVEC proliferation but inhibited their apoptosis to participate in pulmonary vascular remodeling, ultimately leading to HPH through regulation of PINK1-mediated mitophagy signaling. Therefore, PINK1 is a novel therapeutic target for the control of HPH.

IRE1α-XBP1 regulates PDK1-dependent induction of epithelial-mesenchymal transition in non-small cell lung cancer cells.

Mounting evidence indicates that activation of unfolded protein response (UPR) and metabolic reprogramming contribute to cancer cell migration and invasion, but the molecular mechanism of pro-EMT program through a coordinated action of UPR with metabolism has not been defined. In this study, we utilized ER stress-inducing reagent, thapsigargin (TG), to induced pharmacologic ER stress in lung cancer cells. Here. We report that the branch of UPR, IRE1α-XBP1 pathway plays a pivotal role in reprogramming lung cancer cell metabolism. At the molecular level, the expression of pyruvate dehydrogenase kinase-1 (PDK-1) is directly induced by XBP1 as a consequence of UPR activation, thus facilitating aerobic glycolysis and lactate production. We also demonstrated that PDK1 serves as a downstream element of UPR activation in induction of Snail and EMT program. In addition, PDK1-induced Snail was dependent on the lactate production derived from metabolic reprogramming. Our findings reveal a critical role of lactate in pro-invasion events and establishes a direct connection between ER-stress and metabolic reprogramming in facilitating cancer cell progression.

PDK1 Regulates the Lengthening of G1 Phase to Balance RGC Proliferation and Differentiation during Cortical Neurogenesis.

During cortical development, the balance between progenitor self-renewal and neurogenesis is critical for determining the size/morphology of the cortex. A fundamental feature of the developing cortex is an increase in the length of G1 phase in RGCs over the course of neurogenesis, which is a key determinant of progenitor fate choice. How the G1 length is temporally regulated remains unclear. Here, Pdk1, a member of the AGC kinase family, was conditionally disrupted by crossing an Emx1-Cre mouse line with a Pdk1fl/fl line. The loss of Pdk1 led to a shorter cell cycle accompanied by increased RGC proliferation specifically at late rather than early/middle neurogenic stages, which was attributed to impaired lengthening of G1 phase. Coincidently, apical-to-basal interkinetic nuclear migration was accelerated in Pdk1 cKO cortices. Consequently, we detected an increased neuronal output at P0. We further showed the significant upregulation of the cell cycle regulator cyclin D1 and its activator Myc in the cKO cortices relative to those of control animals. Overall, we have identified a novel role for PDK1 in cortical neurogenesis. PDK1 functions as an upstream regulator of the Myc-cyclin D1 pathway to control the lengthening of G1 phase and the balance between RGC proliferation and differentiation.

Pyruvate Dehydrogenase Kinase 1 inhibition mediated oxidative phosphorylation enhancement in cartilage promotes osteoarthritis progression.

Osteoarthritis (OA) is a common disease characterized by cartilage degradation. Growing evidence showed that glucose metabolism impacts joint homeostasis and an imbalance between glycolysis and oxidative phosphorylation (OXPHOS) may exacerbate OA progression, however, a definitive link is yet to be established. Here, we report that pyruvate metabolism and oxidative phosphorylation pathway is enriched in OA cartilage through gene set enrichment analysis (GSEA) and expression of Pyruvate Dehydrogenase Kinase 1 (PDK1), an enzyme that can phosphorylate Pyruvate Dehydrogenase (PDH), and inhibit pyruvate fluxes into the tricarboxylic acid (TCA) cycle and to OXPHOS, in articular cartilage is notably reduced through destabilization of medial meniscus (DMM). Moreover, by inhibiting PDK1, cartilage loss is markedly accelerated in DMM-induced OA through extracellular matrix (ECM) degradation and apoptosis of chondrocytes. These results indicate that PDK1 is involved in the progression of OA through accelerating cartilage matrix degradation and synovium inflammation to ameliorate cartilage degeneration.