Although the mTOR-4E-BP1 signaling pathway is implicated in aging and aging-related disorders, the role of 4E-BP1 in regulating human stem cell homeostasis remains largely unknown. Here, we report that the expression of 4E-BP1 decreases along with the senescence of human mesenchymal stem cells (hMSCs). Genetic inactivation of 4E-BP1 in hMSCs compromises mitochondrial respiration, increases mitochondrial reactive oxygen species (ROS) production, and accelerates cellular senescence. Mechanistically, the absence of 4E-BP1 destabilizes proteins in mitochondrial respiration complexes, especially several key subunits of complex III including UQCRC2. Ectopic expression of 4E-BP1 attenuates mitochondrial abnormalities and alleviates cellular senescence in 4E-BP1-deficient hMSCs as well as in physiologically aged hMSCs. These f indings together demonstrate that 4E-BP1 functions as a geroprotector to mitigate human stem cell senescence and maintain mitochondrial homeostasis, particularly for the mitochondrial respiration complex III, thus providing a new potential target to counteract human stem cell senescence.
Mesenchymal Stem Cells/physiology* ; Cellular Senescence ; Homeostasis ; Cell Cycle Proteins/metabolism* ; Adaptor Proteins, Signal Transducing/metabolism* ; Mitochondria/metabolism* ; Electron Transport Complex III/metabolism* ; Humans ; Cells, Cultured

OBJECTIVE: To screen for aberrantly expressed genes in osteosarcoma cells and investigate the role of RHPN2 in regulating the proliferation, apoptosis, migration and tumorigenic abilities of osteosarcoma cells. METHODS: We used GEO2R to analyze the differential gene expression profile between osteosarcoma cells and normal cells in the GSE70414 dataset. RTqPCR and Western blotting were performed to detect RHPN2 expression in osteosarcoma cell lines MG-63, 143B and SAOS2. Two RHPN2-shRNA and a control NC-shRNA were designed to silence the expression of RHPN2 in 143B cells, and CCK8 assay, colony-forming assay, annexin V-FITC/PI staining and scratch assays were carried out to examine the changes in proliferation, apoptosis and migration of the cells. We also established nude mouse models bearing osteosarcoma xenografts derived 143B cells and RHPN2-shRNA-transfected 143B cells, and assessed the effect of RHPN2 silencing on osteosarcoma cell tumorigenesis using HE staining. Kaplan-Meier survival curves were used to analyze the correlation between RHPN2 expression and survival outcomes of patients with osteosarcoma. RESULTS: RHPN2 expression was significantly upregulated in osteosarcoma cell lines MG-63, 143B and SAOS2 (P < 0.01). Silencing of RHPN2 significantly inhibited the proliferation and migration of 143B cells in vitro, promoted cell apoptosis (P < 0.01), and suppressed tumorigenic capacity of the cells in nude mice. A high expression of RHPN2 was significantly correlated with a poor prognosis of patients with osteosarcoma (P < 0.05). CONCLUSION RHPN2 is highly expressed in osteosarcoma cells to promote cell proliferation and migration and inhibits cell apoptosis. A high expression of RHPN2 is associated with a poorer prognosis of the patients with osteosarcoma.
Adaptor Proteins, Signal Transducing/metabolism* ; Animals ; Apoptosis ; Bone Neoplasms/metabolism* ; Carcinogenesis ; Cell Line, Tumor ; Cell Movement/physiology* ; Cell Proliferation/physiology* ; Humans ; Immediate-Early Proteins ; Mice ; Mice, Nude ; Osteosarcoma/metabolism* ; RNA, Small Interfering/genetics*

While several organs in mammals retain partial regenerative capability following tissue damage, the underlying mechanisms remain unclear. Recently, the Hippo signaling pathway, better known for its function in organ size control, has been shown to play a pivotal role in regulating tissue homeostasis and regeneration. Upon tissue injury, the activity of YAP, the major effector of the Hippo pathway, is transiently induced, which in turn promotes expansion of tissue-resident progenitors and facilitates tissue regeneration. In this review, with a general focus on the Hippo pathway, we will discuss its major components, functions in stem cell biology, involvement in tissue regeneration in different organs, and potential strategies for developing Hippo pathway-targeted regenerative medicines.
Adaptor Proteins, Signal Transducing ; metabolism ; Animals ; Homeostasis ; physiology ; Humans ; Phosphoproteins ; metabolism ; Protein-Serine-Threonine Kinases ; metabolism ; Regeneration ; physiology ; Signal Transduction ; physiology

Mammalian pancreatic β-cells play a pivotal role in development and glucose homeostasis through the production and secretion of insulin. Functional failure or decrease in β-cell number leads to type 2 diabetes (T2D). Despite the physiological importance of β-cells, the viability of β-cells is often challenged mainly due to its poor ability to adapt to their changing microenvironment. One of the factors that negatively affect β-cell viability is high concentration of free fatty acids (FFAs) such as palmitate. In this work, we demonstrated that Yes-associated protein (Yap1) is activated when β-cells are treated with palmitate. Our loss- and gain-of-function analyses using rodent insulinoma cell lines revealed that Yap1 suppresses palmitate-induced apoptosis in β-cells without regulating their proliferation. We also found that upon palmitate treatment, re-arrangement of F-actin mediates Yap1 activation. Palmitate treatment increases expression of one of the Yap1 target genes, connective tissue growth factor (CTGF). Our gain-of-function analysis with CTGF suggests CTGF may be the downstream factor of Yap1 in the protective mechanism against FFA-induced apoptosis.
Actins ; metabolism ; Adaptor Proteins, Signal Transducing ; antagonists & inhibitors ; genetics ; metabolism ; Animals ; Apoptosis ; drug effects ; physiology ; Bridged Bicyclo Compounds, Heterocyclic ; pharmacology ; Cell Line, Tumor ; Connective Tissue Growth Factor ; genetics ; metabolism ; pharmacology ; Cytochalasin D ; pharmacology ; Fatty Acids, Nonesterified ; pharmacology ; HEK293 Cells ; Humans ; Immunohistochemistry ; Insulin-Secreting Cells ; cytology ; drug effects ; metabolism ; Mice ; Microscopy, Fluorescence ; Palmitic Acid ; pharmacology ; Phosphoproteins ; antagonists & inhibitors ; genetics ; metabolism ; RNA Interference ; RNA, Small Interfering ; metabolism ; Rats ; Recombinant Proteins ; genetics ; metabolism ; pharmacology ; Thiazolidines ; pharmacology

OBJECTIVEAutophagy is involved in several neurodegenerative diseases and recently its role in acute brain injury has won increasing interest. Spinal cord injuries (SCIs) often lead to permanent neurological deficit. Therefore, in this study, we examined the pro?les of autophagy-linked proteins (MAP-LC3) after SCI to investigate whether the expression of autophagy contributes to neurological deficit after SCI.

METHODSAdult female Sprague-Dawley rats were used and randomly divided into control and SCI groups. All the rates received laminectomy at T8-T10 level. Those in the SCI group received additional exposure of the dorsal surface of the spinal cord, followed by a weight- drop injury. Thereafter we investigated the expression levels of MAP-LC3, beclin-1, Cathepsin D and the beclin-1-binding protein bcl-2 by western blot analysis at 12 h, 24 h, 3 d, 7 d, 21 d and 28 d. One-way ANOVA with Tukey post hoc test was used to compare data between groups.

RESULTSWe observed significant increase in the level of LC3 (LC3-II/LC3-I) at 3 d and 7 d after SCI when compared with the sham group. While the level of beclin-1 and ratio of beclin-1/bcl-2 was found to have increased from 12 h to 24 h after injury. Cathepsin D expression was also elevated at 7 d (P<0.01).

CONCLUSIONBased on the above mentioned data, we proposed that autophagy plays a role in the manifestation of cell injury following SCI.

Adaptor Proteins, Signal Transducing ; metabolism ; Animals ; Apoptosis Regulatory Proteins ; metabolism ; Autophagy ; physiology ; Beclin-1 ; Blotting, Western ; Cathepsin D ; metabolism ; Disease Models, Animal ; Female ; Laminectomy ; Microtubule-Associated Proteins ; metabolism ; Rats ; Rats, Sprague-Dawley ; Spinal Cord Injuries ; metabolism

OBJECTIVETo investigate function of the Lim-only protein(LMO2) in hemangioblast generated from murine embryonic stem cells differentiation to hematopoietic cells.

METHODSThe hemangioblast-specific expression vector with lmo2 or green fluorescence protein gene was constructed, respectively. The murine embryonic stem cells were transfected by the hemangioblast-specific expression vectors. The neomycin-resistance ES cell clones were obtained after having been screened by G418. The cell clones were spontaneously differentiated into embryo bodies(EB) containing hemangioblast.Expression of the hematopoietic genes was investigated by real-time reverse transcription-ploymerase chain reaction during EB differentiation.For the EB cells, blast-cloning forming cells analysis and blood-colony forming unit analysis were then performed, respectively. The numbers of the blasts were counted during hematopoietic differentiation.

RESULTSThe hemangioblast-specific expression vector with lmo2 or green fluorescence protein was transfected into ES cells.The neomycin-resistance ES cells generated EBs from 2.5 days to 10 days.Real time reverse transcription-ploymerase chain reaction analysis indicated that overexpression of lmo2 increased the expression of hematopoietic genes(gata1, tal1, Β-h1, and Β-major globin) during EB formation.Blast-cloning forming cells analysis showed that the numbers of the blasts generated by ES/lmo2 was 2-or 3-fold than those in the controls.The total numbers of the blood-colony forming unit or the numbers of the erythrocyte colony-forming unit generated by ES/lmo2 were 2.5 times or 3 times, respectively, when compared with the controls.

CONCLUSIONLMO2 enhances the proliferation and differentiation of hemangioblasts.

Adaptor Proteins, Signal Transducing ; physiology ; Animals ; Cell Differentiation ; Cell Proliferation ; Cells, Cultured ; Embryonic Stem Cells ; cytology ; Hematopoietic Stem Cells ; cytology ; metabolism ; LIM Domain Proteins ; physiology ; Mice

BACKGROUNDTransient sublethal ischemia is known as ischemic preconditioning, which enables cells and tissues to survive subsequent prolonged lethal ischemic injury. Ischemic preconditioning exerts neuroprotection through phosphatidylinositol 3-kinase (PI3K)/Akt pathway. Cbl-b belongs to the Casitas B-lineage lymphoma (Cbl) family, and it can regulate the cell signal transduction.The roles of ubiquitin ligase Cbl-b and PI3K/Akt pathway and the relationship between them in oxygen-glucose deprivation preconditioning (OGDPC) in PC12 cells were investigated in the present study.

METHODSOxygen and glucose deprivation (OGD) model in PC12 cells was used in the present study. The 3-(4, 5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, nuclear staining with Hoechst 33258, and Western blotting were applied to explore the roles of Cbl-b and PI3K/Akt pathway and the relationship between them in OGDPC in PC12 cells.

RESULTSCell viability was significantly changed by OGD and OGDPC. OGD significantly decreased cell viability compared with the control group (P < 0.05), and preconditioning could rescue this damage was demonstrated by the increase of cell viability (P < 0.05). The expression of Cbl-b was significantly increased after OGD treatment. However, the activation of Akt and GSK3β was greatly inhibited. Preconditioning could inhibit the increase of Cbl-b caused by OGD and increase the activation of Akt and GSK3β. LY294002, a specific inhibitor of PI3K, could effectively inhibit the increase of Akt and GSK3β after preconditioning treatment. It partly inhibited the decrease of Cbl-b expression after preconditioning treatment.

CONCLUSIONUbiquitin ligase Cbl-b and PI3K/Akt pathway are differently involved in OGDPC in PC12 cells.

Adaptor Proteins, Signal Transducing ; genetics ; metabolism ; Animals ; Cell Survival ; Glucose ; deficiency ; Ischemic Preconditioning ; Oxygen ; metabolism ; PC12 Cells ; Phosphatidylinositol 3-Kinase ; genetics ; metabolism ; Proto-Oncogene Proteins c-akt ; genetics ; metabolism ; Proto-Oncogene Proteins c-cbl ; genetics ; metabolism ; Rats ; Signal Transduction ; physiology

Hippo signaling plays a crucial role in growth control and tumor suppression by regulating cell proliferation, apoptosis, and differentiation. How Hippo signaling is regulated has been under extensive investigation. Over the past three years, an increasing amount of data have supported a model of actin cytoskeleton blocking Hippo signaling activity to allow nuclear accumulation of a downstream effector, Yki/Yap/Taz. On the other hand, Hippo signaling negatively regulates actin cytoskeleton organization. This review provides insight on the mutual regulatory mechanisms between Hippo signaling and actin cytoskeleton for a tight control of cell behaviors during animal development, and points out outstanding questions for further investigations.
Actin Cytoskeleton ; physiology ; Adaptor Proteins, Signal Transducing ; genetics ; metabolism ; Animals ; Cell Proliferation ; Drosophila Proteins ; genetics ; metabolism ; Gene Expression Regulation ; Humans ; Intracellular Signaling Peptides and Proteins ; genetics ; metabolism ; Nuclear Proteins ; genetics ; metabolism ; Phosphoproteins ; genetics ; metabolism ; Phosphorylation ; Protein-Serine-Threonine Kinases ; genetics ; metabolism ; Signal Transduction ; Trans-Activators ; genetics ; metabolism ; Transcription Factors ; genetics ; metabolism

BACKGROUNDThe tendency of tumor cells to disperse throughout the liver is a distinct feature of hepatocellular carcinoma (HCC). Nck family adaptor proteins function to regulate actin cytoskeletal reorganization that leads to cell motility. We previously found that Max binding protein (MNT) was differentially expressed in HCC, and interacted with Nck1 by 2-DE. MNT is a protein member of the Myc/Max/Mad network which plays roles in cell proliferation, differentiation, and death. We investigated the effects of MNT on migration of human liver cancer SK-HEP-1 cells to study the migration regulatory role of MNT in HCC cells.

METHODSInteraction between MNT and Nck1 was further validated in hepatoma cells by GST-pull down assay and immunoprecipitation. siRNAs specific to MNT (MNT siRNA) were used to knockdown MNT expression. Western blotting, transwell assay were used to determine the migration potential of cells.

RESULTSInteraction between MNT and Nck1 was validated in hepatoma cells. MNT knockdown promoted the migration of human liver cancer SK-HEP-1 cells (P < 0.01).

CONCLUSIONThe results suggest that MNT, via interaction with Nck1, inhibits hepatoma cell migration.

Adaptor Proteins, Signal Transducing ; genetics ; metabolism ; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors ; genetics ; metabolism ; Blotting, Western ; Cell Differentiation ; genetics ; physiology ; Cell Line, Tumor ; Cell Movement ; genetics ; physiology ; Humans ; Immunoprecipitation ; Liver Neoplasms ; Oncogene Proteins ; genetics ; metabolism ; Protein Binding ; genetics ; physiology ; Repressor Proteins ; genetics ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction

BACKGROUNDCD44v6 plays an important role in invasion and metastasis of tumor, Livin has anti-apoptotic effects. The present study aimed to explore the expression and clinical significance of CD44v6 and Livin in gastric cancer tissue.

METHODSStreptavidin-peroxidase linked immunohistochemical method was used to determine the expression of CD44v6 and Livin in gastric cancer tissue and adjacent normal gastric tissues from 59 patients with histopathologically confirmed gastric cancer, and in gastric tissue specimens of 15 patients with gastric polyps, and 15 patients with chronic non-atrophic gastritis. The chi-square test was used for comparison of the relevant factors, Spearman's rank correlation test was applied for relationship among positive expression of the proteins.

RESULTSThe expresion of CD44v6 was positive in 64.4% of the gastric cancer patients; 5.1%, 0 and 13.3% in specimens of normal tissues adjacent to the cancer tissues, in gastric tissue specimens of patients with gastric polyps, and patients with chronic non-atrophic gastritis, respectively. The expression of Livin was positive in 52.5% of the gastric cancer tissues, 6.8%, 0 and 6.7% in the adjacent normal gastric tissue, specimens of patients with gastric polyps and chronic non-atrophic gastritis, respectively. The expression of CD44v6 was significantly correlated with the depth of invasion, the degree of differentiation, and lymphnode metastasis of gastric cancer (P < 0.05). The positive expression rate of Livin protein was also significantly correlated with degree of differentiation of gastric cancer cells and metastasis to lymphnodes (P < 0.05), but not correlated with the depth of invasion and pathological types (P > 0.05). The expression of CD44v6 and Livin in the gastric cancer tissue was positively correlated (r(s) = 0.286, P = 0.028).

CONCLUSIONSThe increased expression of CD44v6 and Livin in gastric cancer tissue may be closely related with development and progression of gastric cancer. CD44v6 and Livin may be new biological markers of gastric cancer.

Adaptor Proteins, Signal Transducing ; analysis ; physiology ; Aged ; Female ; Humans ; Hyaluronan Receptors ; analysis ; physiology ; Immunohistochemistry ; Inhibitor of Apoptosis Proteins ; analysis ; physiology ; Male ; Middle Aged ; Neoplasm Proteins ; analysis ; physiology ; Stomach Neoplasms ; chemistry ; metabolism ; pathology