Treponema pallidum membrane protein Tp47 induced autophagy and inhibited cell migration in HMC3 cells via the PI3K/AKT/FOXO1 pathway

The migratory ability of microglia facilitates their rapid transport to a site of injury to kill and remove pathogens. However, the effect of Treponema pallidum membrane proteins on microglia migration remains unclear. The effect of Tp47 on the migration ability and autophagy and related mechanisms were investigated using the human microglial clone 3 cell line. Tp47 inhibited microglia migration, the expression of autophagy-associated protein P62 decreased, the expression of Beclin-1 and LC3-II/LC3-I increased, and the autophagic flux increased in this process. Furthermore, autophagy was significantly inhibited, and microglial cell migration was significantly increased after neutralisation with an anti-Tp47 antibody. In addition, Tp47 significantly inhibited the expression of p-PI3K, p-AKT, and p-mTOR proteins, and the sequential activation of steps in the PI3K/AKT/mTOR pathways effectively prevented Tp47-induced autophagy. Moreover, Tp47 significantly inhibited the expression of p-FOXO1 protein and promoted FOXO1 nuclear translocation. Inhibition of FOXO1 effectively suppressed Tp47-induced activation of autophagy and inhibition of migration. Treponema pallidum membrane protein Tp47-induced autophagy and inhibited cell migration in HMC3 Cells via the PI3K/AKT/FOXO1 pathway. These data will contribute to understanding the mechanism by which T. pallidum escapes immune killing and clearance after invasion into the central nervous system.     

Binding of Avibirnavirus VP3 to the PIK3C3-PDPK1 complex inhibits autophagy by activating the AKT-MTOR pathway

ABSTRACT

Macroautophagy/autophagy is a host natural defense response. Viruses have developed various strategies to subvert autophagy during their life cycle. Recently, we revealed that autophagy was activated by binding of Avibirnavirus to cells. In the present study, we report the inhibition of autophagy initiated by PIK3C3/VPS34 via the PDPK1-dependent AKT-MTOR pathway. Autophagy detection revealed that viral protein VP3 triggered inhibition of autophagy at the early stage of Avibirnavirus replication. Subsequent interaction analysis showed that the CC1 domain of VP3 disassociated PIK3C3-BECN1 complex by direct interaction with BECN1 and blocked autophagosome formation, while the CC3 domain of VP3 disrupted PIK3C3-PDPK1 complex via directly binding to PIK3C3 and inhibited both formation and maturation of autophagosome. Furthermore, we found that PDPK1 activated AKT-MTOR pathway for suppressing autophagy via binding to AKT. Finally, we proved that CC3 domain was critical for role of VP3 in regulating replication of Avibirnavirus through autophagy. Taken together, our study identified that Avibirnavirus VP3 links PIK3C3-PDPK1 complex to AKT-MTOR pathway and inhibits autophagy, a critical step for controlling virus replication.     

Iron overload threatens the growth of osteoblast cells via inhibiting the PI3K/AKT/FOXO3a/DUSP14 signaling pathway

Iron overload is a common stress in the development of cells. Growing evidence has indicated that iron overload is associated with osteoporosis. Therefore, enhancing the understanding of iron overload would benefit the development of novel approaches to the treatment of osteoporosis. The purpose of the present study was to analyze the effect of iron overload on osteoblast cells, via the MC3T3-E1 cell line, and to explore its possible underlying molecular mechanisms. Ferric ammonium citrate (FAC) was utilized to simulate iron overload conditions in vitro. FAC-induced iron overload strongly suppressed proliferation of osteoblast cells and induced apoptosis. Moreover, iron overload strongly suppressed the expression of dual-specificity phosphatase 14 (DUSP14). Additionally, overexpression of DUSP14 protected osteoblast cells from the deleterious effects of iron overload, and this protective effect was mediated by FOXO3a. Additionally, matrine rescued the function of DUSP14 in osteoblast cells. Most importantly, our analysis demonstrated the essential role of the PI3K/AKT/FOXO3a/DUSP14 signaling pathway in the defense against iron overload in osteoblast cells. Overall, our results not only elucidate deleterious effects of iron overload, but also unveil its possible signaling pathway in osteoblast cells.     

Photobiomodulation reduces oxidative stress in diabetic wounded fibroblast cells by inhibiting the FOXO1 signaling pathway

This study aimed to elucidate the underlying molecular mechanism of photobiomodulation (PBM) in attenuating oxidative stress in diabetic wounded fibroblast cells. Cell models were exposed to PBM at a wavelength of 660 nm (fluence of 5 J/cm², and power density of 11.2 mW/cm²) or 830 nm (fluence of 5 J/cm², and power density of 10.3 mW/cm²). Non-irradiated cell models were used as controls. Cellular migration was determined at regular time intervals (0, 12, 24 and 48 h) using inverted light microscopy. Cell viability was determined by the Trypan blue exclusion assay. The levels of enzymic antioxidants superoxide dismutase (SOD), catalase (CAT), and heme oxygenase (HMOX1) were determined by the enzyme linked immunosorbent assay (ELISA). The alteration in the levels of AKT and FOXO1 was determined by immunofluorescence and western blotting. Upon PBM treatment, elevated oxidative stress was reversed in diabetic and diabetic wounded fibroblast cells. The reduced oxidative stress was represented by decreased FOXO1 levels and increased levels of SOD, CAT and HMOX1. This might be due to the activation of the AKT signaling pathway. This study concluded that treatment with PBM progressed diabetic wound healing by attenuating oxidative stress through inhibition of the FOXO1 signaling pathway.Electronic supplementary materialThe online version of this article (10.1007/s12079-020-00588-x) contains supplementary material, which is available to authorized users.     

MCM7 silencing promotes cutaneous melanoma cell autophagy and apoptosis by inactivating the AKT1/mTOR signaling pathway

Cutaneous melanoma (CM) has become a major public health concern. Studies illustrate that minichromosome maintenance protein 7 (MCM7) participate in various diseases including skin disease. Our study aimed to study the effects of MCM7 silencing on CM cell autophagy and apoptosis by modulating the AKT threonine kinase 1 (AKT1)/mechanistic target of rapamycin kinase (mTOR) signaling pathway. Initially, microarray analysis was used to screen the CM-related gene expression data as well as differentially expressed genes. Subsequently, MCM7 expression vector and lentivirus RNA used for MCM7 silencing (LV-shRNA-MCM7) were constructed, and these vectors, dimethyl sulfoxide (DMSO) and AKT activator SC79 were then introduced into CM cell line SK-MEL-2 to validate the role of MCM7 in cell autophagy, viability, apoptosis, cell cycle, migration, and invasion. To further investigate the regulatory mechanisms of MCM7 in CM progress, the expression of MCM7, AKT1, mTOR, cyclin D1, as well as autophagy and apoptosis relative factors, such as LC3B, SOD2, DJ-1, p62, Bcl-2, Bax, and caspase-3 in melanoma cells was determined. MCM7 might mediate the AKT1/mTOR signaling pathway to influence the progress of melanoma. MCM7 silencing contributed to the increased expression of Bax, capase-3, and autophagy-related genes (LC3B, SOD2, and DJ-1), but decreased the expression of Bcl-2, which suggested that MCM7 silencing promoted autophagy and cell apoptosis. At the same time, MCM7 silencing also attenuated cell viability, invasion, and migration, and reduced the cyclin D1 expression and protein levels of p-AKT1 and p-mTOR. Taken together, MCM7 silencing inhibited CM via inactivation of the AKT1/mTOR signaling pathway.     

Abamectin induces apoptosis and autophagy by inhibiting reactive oxygen species‐mediated PI3K/AKT signaling in MGC803 cells

Abamectin (ABA) is one of the most widely used compounds in agriculture and veterinary medicine. However, the cytotoxicity of ABA in human gastric cells is utterly unknown. In this study, ABA suppressed the proliferation of MGC803 cells by arresting the cell cycle at the G0/G1‐phase. Moreover, ABA induced mitochondrial‐mediated apoptosis by inducing the loss of mitochondrial membrane potential, upregulation of Bax/Bcl‐2, and activation of caspase‐3. ABA significantly improved the LC3‐II/LC3‐I ratio and reduced P62 protein expression in a dose‐dependent manner. Through detection of the reactive oxygen species (ROS) levels, we found ABA induced the accumulation of intracellular ROS and then reduced PI3K/AKT signaling activation related to MGC803 cell apoptosis and autophagy. Our results indicate that ABA exerts cytotoxic effects on human MGC803 cells through apoptosis and autophagy by inhibiting ROS‐mediated PI3K/AKT signaling. Furthermore, ABA may be a potential risk to human gastric health.     

GADD45A inhibits autophagy by regulating the interaction between BECN1 and PIK3C3

GADD45A is a TP53-regulated and DNA damage-inducible tumor suppressor protein, which regulates cell cycle arrest, apoptosis, and DNA repair, and inhibits tumor growth and angiogenesis. However, the function of GADD45A in autophagy remains unknown. In this report, we demonstrate that GADD45A plays an important role in regulating the process of autophagy. GADD45A is able to decrease LC3-II expression and numbers of autophagosomes in mouse tissues and different cancer cell lines. Using bafilomycin A₁ treatment, we have observed that GADD45A regulates autophagosome initiation. Likely, GADD45A inhibition of autophagy is through its influence on the interaction between BECN1 and PIK3C3. Immunoprecipitation and GST affinity isolation assays exhibit that GADD45A directly interacts with BECN1, and in turn dissociates the BECN1-PIK3C3 complex. Furthermore, we have mapped the 71 to 81 amino acids of the GADD45A protein that are necessary for the GADD45A interaction with BECN1. Knockdown of BECN1 can abolish autophagy alterations induced by GADD45A. Taken together, these findings provide the novel evidence that GADD45A inhibits autophagy via impairing the BECN1-PIK3C3 complex formation.     

Ganoderic acid A holds promising cytotoxicity on human glioblastoma mediated by incurring apoptosis and autophagy and inactivating PI3K/AKT signaling pathway

Ganoderic acid A (GA‐A), recognized as a lanostanetriterpene isolated from Ganoderma lucidum, demonstrates an efficient antitumor activity in multiple cancers. To date, it is unclear whether and how GA‐A functions on human glioblastoma (GBM). To unravel the functional significance of GA‐A on human glioblastoma (GBM), the cell‐counting kit‐8 and transwell assays were used to detect proliferation, migration, and invasion of human GBM cell after GA‐A treatment. Then, we utilized the flow cytometry and western blot to further evaluate the effect of GA‐A on GBM cell. Further, activities of autophagy and PI3K/AKT signaling were assessed by Western blot assay. We found that GA‐A significantly inhibited proliferation, migration, and invasion of GBM cell. Additionally, GA‐A markedly triggered cell apoptosis, which incarnated an elevation trend in apoptotic percentage, simultaneously, an increased level of proapoptosis protein (Bax and active caspase‐3) and a decreased level of antiapoptosis protein (Bcl‐2), induced by GA‐A treatment. Meanwhile, levels of two well‐known autophagy markers (beclin 1 and LC3 II) increased while another autophagic substrate (P‐62) was reduced. Moreover, the expressions levels of phosphorylated AKT, mTOR, p‐P70S6K, and cyclin D1 in the PI3K/AKT pathway were significantly reduced, which revealed GA‐A repressed the activation of PI3K/AKT signaling pathway. Collectively, these results indicate that GA‐A may encourage U251 cell growth and invasion/migration inhibition, apoptosis, and autophagy through the inactivation of PI3K/AKT signaling pathway in human GBM. Hence, GA‐A may be a potent antitumorigenic agent for human GBM in future clinical practice.     

DMBT1 suppresses progression of gallbladder carcinoma through PI3K/AKT signaling pathway by targeting PTEN

ABSTRACT

Gallbladder carcinoma (GBC) is a highly lethal malignancy of the gastrointestinal tract. Despite extensive research, the underlying molecular mechanism of GBC remains largely unclear. Deleted in malignant brain tumors 1 (DMBT1) is low-expression during cancer progression and as a potential tumor-suppressor gene in various types of cancer. However, its role in Gallbladder cancer remains poorly understood. Here, we found that DMBT1 was significantly low-expression and deletion of copy number in GBC tissues by qRT-PCR and Western blot. Overexpression of DMBT1 impaired survival, promoted apoptosis in GBC cells in vitro, and inhibited tumor progression in vivo. Further study of underlying mechanisms demonstrated that DMBT1 combined with PTEN which could stabilize PTEN protein, resulting in inhibiting the activation of PI3K/AKT signaling pathway. Our study revealed a new sight of DMBT1 as a tumor-suppressor gene on the PI3K/AKT pathway in GBC, which may be a potential therapeutic target for improving treatment.     

Dual inhibition of autophagy and the AKT pathway in prostate cancer

Genetic inactivation of PTEN through either gene deletion or mutation is common in metastatic prostate cancer, leading to activation of the phosphoinositide 3-kinase (PI3K-AKT) pathway, which is associated with poor clinical outcomes. The PI3K-AKT pathway plays a central role in various cellular processes supporting cell growth and survival of tumor cells. To date, therapeutic approaches to develop inhibitors targeting the PI3K-AKT pathway have failed in both pre-clinical and clinical trials. We showed that a novel AKT inhibitor, AZD5363, inhibits the AKT downstream pathway by reducing p-MTOR and p-RPS6KB/p70S6K. We specifically reported that AZD5363 monotherapy induces G2 growth arrest and autophagy, but fails to induce significant apoptosis in PC-3 and DU145 prostate cancer cell lines. Blocking autophagy using pharmacological inhibitors (3-methyladenine, chloroquine and bafilomycin A₁) or genetic inhibitors (siRNA targeting ATG3 and ATG7) enhances cell death induced by AZD5363 in these prostate cancer cells. Importantly, the combination of AZD5363 with chloroquine significantly reduces tumor volume compared with the control group, and compared with either drug alone in prostate tumor xenograft models. Taken together, these data demonstrate that AKT inhibitor AZD5363, synergizes with the lysosomotropic inhibitor of autophagy, chloroquine, to induce apoptosis and delay tumor progression in prostate cancer models that are resistant to monotherapy, with AZD5363 providing a new therapeutic approach potentially translatable to patients.     

Association of common genetic variation in the insulin/IGF1 signaling pathway with human longevity

The insulin/IGF1 signaling pathways affect lifespan in several model organisms, including worms, flies and mice. To investigate whether common genetic variation in this pathway influences lifespan in humans, we genotyped 291 common variants in 30 genes encoding proteins in the insulin/IGF1 signaling pathway in a cohort of elderly Caucasian women selected from the Study of Osteoporotic Fractures (SOF). The cohort included 293 long-lived cases (lifespan ≥ 92 years (y), mean ± standard deviation (SD) = 95.3 ± 2.2y) and 603 average-lifespan controls (lifespan ≤ 79y, mean = 75.7 ± 2.6y). Variants were selected for genotyping using a haplotype-tagging approach. We found a modest excess of variants nominally associated with longevity. Nominally significant variants were then replicated in two additional Caucasian cohorts including both males and females: the Cardiovascular Health Study and Ashkenazi Jewish Centenarians. An intronic single nucleotide polymorphism in AKT1 , rs3803304, was significantly associated with lifespan in a meta-analysis across the three cohorts (OR = 0.78 95%CI = 0.68–0.89, adjusted P  = 0.043); two intronic single nucleotide polymorphisms in FOXO3A demonstrated a significant lifespan association among women only (rs1935949, OR = 1.35, 95%CI = 1.15–1.57, adjusted P  = 0.0093). These results demonstrate that common variants in several genes in the insulin/IGF1 pathway are associated with human lifespan.