Mitotic gene regulation by the N-MYC-WDR5-PDPK1 nexus.

BACKGROUND: During mitosis the cell depends on proper attachment and segregation of replicated chromosomes to generate two identical progeny. In cancers defined by overexpression or dysregulation of the MYC oncogene this process becomes impaired, leading to genomic instability and tumor evolution. Recently it was discovered that the chromatin regulator WDR5-a critical MYC cofactor-regulates expression of genes needed in mitosis through a direct interaction with the master kinase PDPK1. However, whether PDPK1 and WDR5 contribute to similar mitotic gene regulation in MYC-overexpressing cancers remains unclear. Therefore, to characterize the influence of WDR5 and PDPK1 on mitotic gene expression in cells with high MYC levels, we performed a comparative transcriptomic analysis in neuroblastoma cell lines defined by MYCN-amplification, which results in high cellular levels of the N-MYC protein. RESULTS: Using RNA-seq analysis, we identify the genes regulated by N-MYC and PDPK1 in multiple engineered CHP-134 neuroblastoma cell lines and compare them to previously published gene expression data collected in CHP-134 cells following inhibition of WDR5. We find that as expected N-MYC regulates a multitude of genes, including those related to mitosis, but that PDPK1 regulates specific sets of genes involved in development, signaling, and mitosis. Analysis of N-MYC- and PDPK1-regulated genes reveals a small group of commonly controlled genes associated with spindle pole formation and chromosome segregation, which overlap with genes that are also regulated by WDR5. We also find that N-MYC physically interacts with PDPK1 through the WDR5-PDPK1 interaction suggesting regulation of mitotic gene expression may be achieved through a N-MYC-WDR5-PDPK1 nexus. CONCLUSIONS: Overall, we identify a small group of genes highly enriched within functional gene categories related to mitotic processes that are commonly regulated by N-MYC, WDR5, and PDPK1 and suggest that a tripartite interaction between the three regulators may be responsible for setting the level of mitotic gene regulation in N-MYC amplified cell lines. This study provides a foundation for future studies to determine the exact mechanism by which N-MYC, WDR5, and PDPK1 converge on cell cycle related processes.

Single-cell RNA sequencing reveals the mechanism of PI3K/AKT/mTOR signaling pathway activation in lung adenocarcinoma by KRAS mutation.

BACKGROUND: Aberrant activation of the phosphatidlinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway has been shown to play an important role in lung adenocarcinoma (LUAD). The effect of KRAS mutations, one of the important signatures of LUAD, on the PI3K/AKT/mTOR pathway in LUAD remains unclear. METHODS: The Seurat package and principal component analysis were used for cell categorization of single-cell RNA sequencing data of LUAD. The AUCell score was used to assess the activity of the PI3K/AKT/mTOR pathway. Meanwhile, using the gene expression profiles and mutation profiles in the The Cancer Genome Atlas dataset, LUAD patients were categorized into KRAS-mutant (KRAS-MT) and KRAS-wild-types (KRAS-WT), and the corresponding enrichment scores were calculated using gene set enrichment analysis analysis. Finally, the subpopulation of cells with the highest pathway activity was identified, the copy number variation profile of this subpopulation was inscribed using the inferCNV package and the CMap database was utilized to make predictions for drugs targeting this subpopulation. RESULTS: There is higher PI3K/AKT/mTOR pathway activity in LUAD epithelial cells with KRAS mutations, and high expression of KRAS, PIK3CA, AKT1 and PDPK1. In particular, we found significantly higher levels of pathway activity and associated gene expression in KRAS-MT than in KRAS-WT. We identified the highest pathway activity on a subpopulation of GRB2+ epithelial cells and the presence of amplified genes within its pathway. Finally, drugs were able to target GRB2+ epithelial cell subpopulations, such as wortmannin, palbociclib and angiogenesis inhibitor. CONCLUSIONS: The present study provides a basic theory for the activation of the PI3K/AKT/mTOR signaling pathway as a result of KRAS mutations.

Non-allergic eye rubbing is a major behavioral risk factor for keratoconus.

Since the environmental, behavioral, and socioeconomic factors in the etiology of keratoconus (KTCN) remain poorly understood, we characterized them as features influencing KTCN phenotype, and especially affecting the corneal epithelium (CE). In this case-control study, 118 KTCN patients and 73 controls were clinically examined and the Questionnaire covering the aforementioned aspects was completed and then statistically elaborated. Selected KTCN-specific findings were correlated with the outcomes of the RNA-seq assessment of the CE samples. Male sex, eye rubbing, time of using a computer after work, and dust in the working environment, were the substantial KTCN risk factors identified in multivariate analysis, with ORs of 8.66, 7.36, 2.35, and 5.25, respectively. Analyses for genes whose expression in the CE was correlated with the eye rubbing manner showed the enrichment in apoptosis (TP53, BCL2L1), chaperon-related (TLN1, CTDSP2, SRPRA), unfolded protein response (NFYA, TLN1, CTDSP2, SRPRA), cell adhesion (TGFBI, PTPN1, PDPK1), and cellular stress (TFDP1, SRPRA, CAPZB) pathways. Genes whose expression was extrapolated to the allergy status didn't contribute to IgE-related or other inflammatory pathways. Presented findings support the hypothesis of chronic mechanical corneal trauma in KTCN. Eye-rubbing causes CE damage and triggers cellular stress which through its influence on cell apoptosis, migration, and adhesion affects the KTCN phenotype.

Deletion of PDK1 Caused Cardiac Malmorphogenesis and Heart Defects Due to Profound Protein Phosphorylation Changes Mediated by SHP2.

Phosphoinositide-dependent protein kinase-1 (PDK1), a master kinase and involved in multiple signaling transduction, participates in regulating embryonic cardiac development and postnatal cardiac remodeling. Germline PDK1 knockout mice displayed no heart development; in this article, we deleted PDK1 in heart tissue with different cre to characterize the temporospatial features and find the relevance with congenital heart disease(CHD), furthermore to investigate the underlying mechanism. Knocking out PDK1 with Nkx2.5-cre, the heart showed prominent pulmonic stenosis. Ablated PDK1 with Mef2cSHF-cre, the second heart field (SHF) exhibited severe hypoplasia. And deleted PDK1 with αMHC-cre, the mice displayed dilated heart disease, protein analysis indicated PI3K and ERK were activated; meanwhile, PDK1-AKT-GSK3, and S6K-S6 were disrupted; phosphorylation level of Akt473, S6k421/424, and Gsk3α21 enhanced; however, Akt308, S6k389, and Gsk3ß9 decreased. In mechanism investigation, we found SHP2 membrane localization and phosphorylation level of SHP2542 elevated, which suggested SHP2 likely mediated the disruption.

MiR-139 Affects Radioresistance in Esophageal Cancer by Targeting the PDK1/AKT/Cyclin D1 Signaling Pathway.

We explored the mechanism by which miR-139 modulates radioresistance of esophageal cancer (EC). The radioresistant cell line KYSE150R was obtained from the parental KYSE150 cell line by fractionated irradiation (15×2 Gy; total dose of 30 Gy). The cell cycle was assessed by flow cytometry. A gene profiling study was conducted to detect the expression of genes related to the radioresistance of EC. In the KYSE150R line, flow cytometry revealed increased number of G1-phase cells and decreased number of G2-phase cells; the expression of miR-139 increased. Knockdown of miR-139 decreased radioresistance and changed the distribution of cell cycle phases in KYSE150R cells. Western blotting showed that miR-139 knockdown increased the expression levels of cyclin D1, p-AKT, and PDK1. However, PDK1 inhibitor GSK2334470 reversed this effect for p-AKT and cyclin D1 expression. A luciferase reporter assay indicated that miR-139 directly bound to the PDK1 mRNA 3'-UTR. Analysis of the clinical data from 110 patients with EC showed an association of miR-139 expression with the TNM stage and the effect of therapy. MiR-139 expression significantly correlated with EC and progression-free survival. In conclusion, miR-139 enhances the radiosensitivity of EC by regulating the cell cycle through the PDK1/Akt/Cyclin D1 signaling pathway.

Extracellular vesicle-derived circCEBPZOS attenuates postmyocardial infarction remodeling by promoting angiogenesis via the miR-1178-3p/PDPK1 axis.

Emerging studies indicate that extracellular vesicles (EVs) and their inner circular RNAs (circRNAs), play key roles in the gene regulatory network and cardiovascular repair. However, our understanding of EV-derived circRNAs in cardiac remodeling after myocardial infarction (MI) remains limited. Here we show that the level of circCEBPZOS is downregulated in serum EVs of patients with the adverse cardiac remodeling compared with those without post-MI remodeling or normal subjects. Loss-of-function approaches in vitro establish that circCEBPZOS robustly promote angiogenesis. Overexpression of circCEBPZOS in mice attenuates MI-induced left ventricular dysfunction, accompanied by a larger functional capillary network at the border zone. Further exploration of the downstream target gene indicates that circCEBPZOS acts as a competing endogenous RNA by directly binding to miR-1178-3p and thereby inducing transcription of its target gene phosphoinositide-dependent kinase-1 (PDPK1). Together, our results reveal that circCEBPZOS attenuates detrimental post-MI remodeling via the miR-1178-3p/PDPK1 axis, which facilitates revascularization, ultimately improving the cardiac function.

Molecular regulation of polycystic ovary syndrome: altered gene expression levels in mouse models pretreatment and post-treatment.

Polycystic ovary syndrome (PCOS) is a complex disorder and genetic factors are believed to play a role. The main aim was to investigate expression levels of genes involved in PI3K/AKT signalling pathway pretreatment and post-treatment. Mouse models of PCOS were generated. Group one included control mice with no polycystic ovaries (n = 4), Group 2 included a PCOS mouse model (n = 8), Group 3 included PCOS mice treated with clomiphene citrate (n = 7) and Group 4 included PCOS mice treated with clomiphene citrate, metformin and pioglitazone (n = 8). Histochemical analyses were performed. Total RNA was extracted and cDNA was synthesized. Irs, Akt1 and Akt2, mTor and Pdpk1 gene expression levels were evaluated by RT-PCR amplification. In Group 1, cortex and medulla were evaluated as normal; in Group 2, ovarian cortex was composed of immature oocytes and cystic follicles with atretic follicles. In Groups 3 and 4, follicles were in the process of normal follicle differentiation. The expression levels of Akt1 and Pi3k were significantly different (P < 0.0001) between Groups 1 and 2. The significant differences in expression levels of Pi3k and Akt1 were also observed between the Group 1 and both Groups 3 and 4 (P < 0.0001). Furthermore, significant variations of the expression levels of mTor between Groups 1 and 4 were observed. The extrapolation of results of this study may imply that follicular development may be regulated by molecular pathways involving Pi3k, Akt1 and mTor expression. Therefore, genes in the PI3K/AKT pathway may have a direct regulatory role in the development of PCOS.

The 3-phosphoinositide-dependent protein kinase 1 is an essential upstream activator of protein kinase A in malaria parasites.

Cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) signalling is essential for the proliferation of Plasmodium falciparum malaria blood stage parasites. The mechanisms regulating the activity of the catalytic subunit PfPKAc, however, are only partially understood, and PfPKAc function has not been investigated in gametocytes, the sexual blood stage forms that are essential for malaria transmission. By studying a conditional PfPKAc knockdown (cKD) mutant, we confirm the essential role for PfPKAc in erythrocyte invasion by merozoites and show that PfPKAc is involved in regulating gametocyte deformability. We furthermore demonstrate that overexpression of PfPKAc is lethal and kills parasites at the early phase of schizogony. Strikingly, whole genome sequencing (WGS) of parasite mutants selected to tolerate increased PfPKAc expression levels identified missense mutations exclusively in the gene encoding the parasite orthologue of 3-phosphoinositide-dependent protein kinase-1 (PfPDK1). Using targeted mutagenesis, we demonstrate that PfPDK1 is required to activate PfPKAc and that T189 in the PfPKAc activation loop is the crucial target residue in this process. In summary, our results corroborate the importance of tight regulation of PfPKA signalling for parasite survival and imply that PfPDK1 acts as a crucial upstream regulator in this pathway and potential new drug target.

PDK1 Is Required for Maintenance of CD4+ Foxp3+ Regulatory T Cell Function.

Regulatory T (Treg) cells have an essential role in maintaining immune homeostasis, in part by suppressing effector T cell functions. Phosphoinositide-dependent kinase 1 (PDK1) is a pleiotropic kinase that acts as a key effector downstream of PI3K in many cell types. In T cells, PDK1 has been shown to be critical for activation of NF-κB and AKT signaling upon TCR ligation and is therefore essential for effector T cell activation, proliferation, and cytokine production. Using Treg cell-specific conditional deletion, we now demonstrate that PDK1 is also essential for Treg cell suppressive activity in vivo. Ablation of Pdk1 specifically in Treg cells led to systemic, lethal, scurfy-like inflammation in mice. Genome-wide analysis confirmed that PDK1 is essential for the regulation of key Treg cell signature gene expression and, further, suggested that PDK1 acts primarily to control Treg cell gene expression through regulation of the canonical NF-κB pathway. Consistent with these results, the scurfy-like phenotype of mice lacking PDK1 in Treg cells was rescued by enforced activation of NF-κB downstream of PDK1. Therefore, PDK1-mediated activation of the NF-κB signaling pathway is essential for regulation of Treg cell signature gene expression and suppressor function.

Role of PDK1 in skeletal muscle hypertrophy induced by mechanical load.

Phosphatidylinositol 3-kinase (PI3K) plays an important role in protein metabolism and cell growth. We here show that mice (M-PDK1KO mice) with skeletal muscle-specific deficiency of 3'-phosphoinositide-dependent kinase 1 (PDK1), a key component of PI3K signaling pathway, manifest a reduced skeletal muscle mass under the static condition as well as impairment of mechanical load-induced muscle hypertrophy. Whereas mechanical load-induced changes in gene expression were not affected, the phosphorylation of ribosomal protein S6 kinase (S6K) and S6 induced by mechanical load was attenuated in skeletal muscle of M-PDK1KO mice, suggesting that PDK1 regulates muscle hypertrophy not through changes in gene expression but through stimulation of kinase cascades such as the S6K-S6 axis, which plays a key role in protein synthesis. Administration of the ß2-adrenergic receptor (AR) agonist clenbuterol activated the S6K-S6 axis in skeletal muscle and induced muscle hypertrophy in mice. These effects of clenbuterol were attenuated in M-PDK1KO mice, and mechanical load-induced activation of the S6K-S6 axis and muscle hypertrophy were inhibited in mice with skeletal muscle-specific deficiency of ß2-AR. Our results suggest that PDK1 regulates skeletal muscle mass under the static condition and that it contributes to mechanical load-induced muscle hypertrophy, at least in part by mediating signaling from ß2-AR.

The kinase PDK1 is critical for promoting T follicular helper cell differentiation.

The kinase PDK1 is a crucial regulator for immune cell development by connecting PI3K to downstream AKT signaling. However, the roles of PDK1 in CD4+ T cell differentiation, especially in T follicular helper (Tfh) cell, remain obscure. Here we reported PDK1 intrinsically promotes the Tfh cell differentiation and germinal center responses upon acute infection by using conditional knockout mice. PDK1 deficiency in T cells caused severe defects in both early differentiation and late maintenance of Tfh cells. The expression of key Tfh regulators was remarkably downregulated in PDK1-deficient Tfh cells, including Tcf7, Bcl6, Icos, and Cxcr5. Mechanistically, ablation of PDK1 led to impaired phosphorylation of AKT and defective activation of mTORC1, resulting in substantially reduced expression of Hif1α and p-STAT3. Meanwhile, decreased p-AKT also suppresses mTORC2-associated GSK3ß activity in PDK1-deficient Tfh cells. These integrated effects contributed to the dramatical reduced expression of TCF1 and ultimately impaired the Tfh cell differentiation.

Impact of WIN site inhibitor on the WDR5 interactome.

The chromatin-associated protein WDR5 is a promising pharmacological target in cancer, with most drug discovery efforts directed against an arginine-binding cavity in WDR5 called the WIN site. Despite a clear expectation that WIN site inhibitors will alter the repertoire of WDR5 interaction partners, their impact on the WDR5 interactome remains unknown. Here, we use quantitative proteomics to delineate how the WDR5 interactome is changed by WIN site inhibition. We show that the WIN site inhibitor alters the interaction of WDR5 with dozens of proteins, including those linked to phosphatidylinositol 3-kinase (PI3K) signaling. As proof of concept, we demonstrate that the master kinase PDPK1 is a bona fide high-affinity WIN site binding protein that engages WDR5 to modulate transcription of genes expressed in the G2 phase of the cell cycle. This dataset expands our understanding of WDR5 and serves as a resource for deciphering the action of WIN site inhibitors.

Long noncoding Mirt2 reduces apoptosis to alleviate myocardial infarction through regulation of the miR-764/PDK1 axis.

Acute myocardial infarction (AMI) is a common clinical cardiovascular disease, which is the leading cause of death and disability worldwide. Abnormal expression of long noncoding RNAs (lncRNA) is reported to be related to myocardial dysfunctions such as myocardial infarction (MI). In this study, we aimed to investigate the role of lncRNA myocardial infarction-related transcription factors 2 (Mirt2) in AMI and the underlying molecular mechanisms in vivo and in vitro. In vivo AMI model was established by occlusion of the left anterior descending coronary artery. Rats were randomly divided into two groups (five rats per group): the sham group and the AMI group. H9c2 cells were cultured under hypoxia for 4 h and then cultured under normoxia to establish the in vitro hypoxia reoxygenation (H/R) model. Our study shows that the myocardial infarct size and the apoptosis in AMI rats were both significantly increased, indicating that the AMI rat model was successfully established. Additionally, the levels of Mirt2 in AMI rats were increased significantly. Knockdown of Mirt2 by shRNA (shMirt2) had no significant effect on apoptosis and MI in sham rats, but significantly promoted apoptosis and MI in AMI rats. In vitro experiments showed that shMirt2 significantly decreased the level of Mirt2 in H9c2 cells and H9c2 cells treated with H/R. It is worth noting that shMirt2 had no significant effect on H9c2 cells, but significantly increased the levels of oxidative stress markers (malondialdehyde and lactate dehydrogenase), and also increased the number of apoptosis of H/R-treated H9c2 cells. Further mechanistic analysis showed that Mirt2 could protect MI and apoptosis in AMI rats by competitively adsorbing miR-764 and reducing the inhibitory effect of miR-764 on 3-phosphoinositide-dependent kinase 1 (PDK1). More importantly, after overexpression of Mirt2, MI and apoptosis were significantly improved in AMI rats, indicating that Mirt2 showed a protective effect in AMI rats. In summary, these findings suggest that that Mirt2 participated in the regulation of MI through the miR-764/PDK1 axis. Therefore, the current findings provide a theoretical basis for the diagnosis and treatment of clinical MI with changes in Mirt2 levels.

Conditional knockout of the PDK-1 gene in osteoblasts affects osteoblast differentiation and bone formation.

Osteoblasts are the main functional cells of bone formation, and they are responsible for the synthesis, secretion, and mineralization of the bone matrix. Phosphatidylinositol-3-kinase/Akt is an important signaling pathway involved in the regulation of cell proliferation, death, and survival. Some studies have shown that 3-phosphoinositide-dependent protein kinase-1 (PDK-1) plays an important role in the phosphorylation of Akt. In the present study, an osteocalcin (OCN) promoter-driven Cre-LoxP system was established to specifically delete the PDK-1 gene in osteoblasts. It was found that the size and weight of PDK-1 conditional gene knockout (cKO) mice were significantly reduced. von Kossa staining and microcomputed tomography showed that the trabecular thickness, trabecular number, and bone volume were significantly decreased, whereas trabecular separation was increased, as compared with wide-type littermates, which were characterized by a decreased bone mass. A model of distal femoral defect was established, and it was found that cKO mice delayed bone defect repair. In osteoblasts derived from PDK-1 cKO mice, the alkaline phosphatase (ALP) secretion and ability of calcium mineralization were significantly decreased, and the expressions of osteoblast-related proteins, runt-related transcription factor 2, OCN, and ALP were also clearly decreased. Moreover, the phosphorylation level of Akt and downstream factor GSK3ß and their response to insulin-like growth factor-1 (IGF-1) decreased clearly. Therefore, we believe that PDK-1 plays a very important role in osteoblast differentiation and bone formation by regulating the PDK-1/Akt/GSK3ß signaling pathway.

Inhibition of class I PI3K enhances chaperone-mediated autophagy.

Chaperone-mediated autophagy (CMA) is the most selective form of lysosomal proteolysis, where individual peptides, recognized by a consensus motif, are translocated directly across the lysosomal membrane. CMA regulates the abundance of many disease-related proteins, with causative roles in neoplasia, neurodegeneration, hepatosteatosis, and other pathologies relevant to human health and aging. At the lysosomal membrane, CMA is inhibited by Akt-dependent phosphorylation of the CMA regulator GFAP. The INS-PI3K-PDPK1 pathway regulates Akt, but its role in CMA is unclear. Here, we report that inhibition of class I PI3K or PDPK1 activates CMA. In contrast, selective inhibition of class III PI3Ks does not activate CMA. Isolated liver lysosomes from mice treated with either of two orally bioavailable class I PI3K inhibitors, pictilisib or buparlisib, display elevated CMA activity, and decreased phosphorylation of lysosomal GFAP, with no change in macroautophagy. The findings of this study represent an important first step in repurposing class I PI3K inhibitors to modulate CMA in vivo.

LncRNA KTN1-AS1 promotes the progression of non-small cell lung cancer via sponging of miR-130a-5p and activation of PDPK1.

Non-small cell lung cancer (NSCLC) is the major cause of cancer-associated death worldwide, but its underlying mechanisms remain to be fully elucidated. Long noncoding RNAs (lncRNAs) are known to play an important role in the aberrant regulation of gene expression in many cancers, including NSCLC. Here, we investigated the involvement of the lncRNA KTN1-AS1 in NSCLC. We found that KTN1-AS1 expression was upregulated in NSCLC tissue and was positively associated with poor prognosis. KTN1-AS1 knockdown inhibited cell growth and proliferation, increased apoptosis, and modulated the expression of cell cycle- and apoptosis-related proteins (cyclin A1, cyclin-dependent kinase 2, Bcl2, and Bax) in NSCLC cell lines and tumour xenografts in nude mice. KTN1-AS1 bound to and directly regulated the expression of miR-130a-5p. Notably, miR-130a-5p overexpression suppressed NSCLC cell proliferation and increased apoptosis in vitro and in vivo, and this effect was reversed by KTN1-AS1 overexpression. Finally, we showed that KTN1-AS1 modulated the expression of 3-phosphoinositide-dependent protein kinase 1 (PDPK1), a miR-130a-5p target and key regulator of autophagy in NSCLC cells. Taken together, our results suggest that the KTN1-AS1/miR-130a-5p/PDPK1 pathway may be a potential therapeutic target for NSCLC.

Long non-coding RNA ABHD11-AS1 boosts gastric cancer development by regulating miR-361-3p/PDPK1 signalling.

Gastric cancer (GC) is one of the most common cancers in gastrointestinal malignant tumours. Long non-coding RNAs were widely reported to play a significant role in the regulation of occurrence or development of tumours. Bioinformatics analysis and a wide range of experiments were conducted to explore the expression status, specific function and molecular mechanism of long non-coding RNA ABHD11 antisense RNA 1 (ABHD11-AS1). ABHD11-AS1 knockdown repressed cell proliferation but enhanced cell apoptosis in function. We proved that miR-361-3p directly combines with the 3'wUTR of PDPK2 and ABHD11-AS1 cooperated with miR-361-3p to modulate PDPK2 mRNA and protein levels. Rescue assays confirmed that the miR-361-3p silence reversed the suppressive effect of ABHD11-AS1 deficiency. In summary, ABHD11-AS1 boosts GC development by regulating miR-361-3p/PDPK1 signalling.

Long Noncoding RNA LNC_000898 Alleviates Cardiomyocyte Apoptosis and Promotes Cardiac Repair After Myocardial Infarction Through Modulating the miR-375/PDK1 Axis.

Increasing evidence has confirmed that both long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) exert key roles in the pathogenesis of myocardial infarction (MI). Previous microarray assay results revealed that lncRNA LNC_000898 expression was significantly downregulated in acute MI. However, the specific function of LNC_000898 on MI is still unclear. Our study was aimed to explore the role of LNC_000898 on cardiac MI injury and investigate its underlying mechanism. The male C57BL/6 mouse was used as cardiac MI injury animal models, and neonatal mouse ventricular cardiomyocytes (NMCMs) exposed to hypoxia were used as an in vitro model. Quantitative real-time polymerase chain reaction analysis, Western blot analysis, Tunel immunofluorescence staining assay, and cardiac echocardiography measurement were conducted to detect corresponding indicators. The results indicated that LNC_000898 expression was downregulated in marginal tissue of MI and in NMCMs exposed to hypoxia. Overexpression of LNC_000898 decreased cardiomyocyte apoptosis both in vivo and in vitro. In addition, we elaborated that LNC_000898 exerts its inhibitory effect on apoptosis after MI through the miR-375/PDK1 axis. Through miR-375 overexpression or silencing PDK1, the biological effects of LNC_000898 on hypoxia-induced NMCM injury were partially reversed. These data not only demonstrate that LNC_000898 could protect the heart against MI injury by regulating miR-375/PDK1 but also provide a new understanding to better protection of MI injury through the LNC_000898/miR-375/PDK1 axis.

PDK1 regulates the survival of the developing cortical interneurons.

Inhibitory interneurons are critical for maintaining the excitatory/inhibitory balance. During the development cortical interneurons originate from the ganglionic eminence and arrive at the dorsal cortex through two tangential migration routes. However, the mechanisms underlying the development of cortical interneurons remain unclear. 3-Phosphoinositide-dependent protein kinase-1 (PDK1) has been shown to be involved in a variety of biological processes, including cell proliferation and migration, and plays an important role in the neurogenesis of cortical excitatory neurons. However, the function of PDK1 in interneurons is still unclear. Here, we reported that the disruption of Pdk1 in the subpallium achieved by crossing the Dlx5/6-Cre-IRES-EGFP line with Pdk1fl/fl mice led to the severely increased apoptosis of immature interneurons, subsequently resulting in a remarkable reduction in cortical interneurons. However, the tangential migration, progenitor pools and cell proliferation were not affected by the disruption of Pdk1. We further found the activity of AKT-GSK3ß signaling pathway was decreased after Pdk1 deletion, suggesting it might be involved in the regulation of the survival of cortical interneurons. These results provide new insights into the function of PDK1 in the development of the telencephalon.

The PDK1-FoxO1 signaling in adipocytes controls systemic insulin sensitivity through the 5-lipoxygenase-leukotriene B4 axis.

Although adipocytes are major targets of insulin, the influence of impaired insulin action in adipocytes on metabolic homeostasis remains unclear. We here show that adipocyte-specific PDK1 (3'-phosphoinositide-dependent kinase 1)-deficient (A-PDK1KO) mice manifest impaired metabolic actions of insulin in adipose tissue and reduction of adipose tissue mass. A-PDK1KO mice developed insulin resistance, glucose intolerance, and hepatic steatosis, and this phenotype was suppressed by additional ablation of FoxO1 specifically in adipocytes (A-PDK1/FoxO1KO mice) without an effect on adipose tissue mass. Neither circulating levels of adiponectin and leptin nor inflammatory markers in adipose tissue differed between A-PDK1KO and A-PDK1/FoxO1KO mice. Lipidomics and microarray analyses revealed that leukotriene B4 (LTB4) levels in plasma and in adipose tissue as well as the expression of 5-lipoxygenase (5-LO) in adipose tissue were increased and restored in A-PDK1KO mice and A-PDK1/FoxO1KO mice, respectively. Genetic deletion of the LTB4 receptor BLT1 as well as pharmacological intervention to 5-LO or BLT1 ameliorated insulin resistance in A-PDK1KO mice. Furthermore, insulin was found to inhibit LTB4 production through down-regulation of 5-LO expression via the PDK1-FoxO1 pathway in isolated adipocytes. Our results indicate that insulin signaling in adipocytes negatively regulates the production of LTB4 via the PDK1-FoxO1 pathway and thereby maintains systemic insulin sensitivity.