Accumulation of unfolded/misfolded proteins in the endoplasmic reticulum (ER) activates the unfolded protein response (UPR). The ATF6 pathway is one of the three major pathways in vertebrates. Although ATF6, a transmembrane-type glycoprotein in the ER, functions as a UPR sensor/transducer, it is an unstable protein with a half-life of approximately 2 h and is constitutively subjected to the ER-associated degradation system with the location of the misfolded part in the ER lumen (ERAD-L). ERAD-L substrates are delivered to the cytosol through the retrotranslocon, which likely contains HRD1 (E3), gp78 (E3), SEL1L (a partner of HRD1), Derlin1/2/3 and Herp1/2. We previously showed that ATF6 represents a novel transmembrane-type ERAD-L substrate requiring both EDEM1/2/3-mediated mannose trimming and SEL1L. Here, by constructing and analyzing chicken DT40 cells deficient in various components of the retrotranslocon, we show that degradation of ATF6 requires Derlin2 or Derlin3 and that Derlin2 and Derlin3 are redundant for ERAD-L of ATF6. We further show that degradation of ATF6 requires Herp1 or Herp2 and that Herp1 and Herp2 are redundant for ERAD-L of ATF6. Furthermore, by investigating five more ERAD-L substrates, we show that SEL1L-dependent substrates require Derlin2/3 and Herp1/2 regardless of their soluble or transmembrane nature. Our results suggest that ERAD-L substrates take several routes to the cytosol. The HRD1-engaged route 1 requires SEL1L, Derlin2 or Derlin3, and Herp1 or Herp2, whereas the HRD1-engaged route 2 does not require them functionally. It remains to be determined whether the latter requires Derlin1 and whether these two routes are compositionally distinct.
Key words: endoplasmic reticulum, proteasome, protein degradation, protein misfolding, ubiquitin
Background: Liver fibrosis is the response of liver diseases that puzzles patients. MiRNAs were involved in the regulating processes of liver fibrosis. This study aims to investigate the effects of ARRB1 mediated by miR-29a and miR-652 on liver fibrosis and its possible mechanism. Methods: Liver fibrosis of mice was induced by intraperitoneal injection of CCl4. Liver function was observed by the levels of alanine transaminase (ALT) and aspartate transaminase (AST). Flow cytometry was used to detect the percent of T helper17 (Th17). ELISA (Enzyme linked immunoassay) was used to detect the levels of Interleukin-17 (IL-17) and Interleukin-22 (IL-22). Real-time PCR was used to detect the expression of IL-17A, IL-22, miR-29a, miR-652 and β-Arrestin 1 Gene (ARRB1). Western blot was used to detect the protein expression of ARRB1. Results: CCl4 supplementation significantly increased the level of ALT and AST, the percent of Th17, the level of IL-17A, IL-22, miR-29a and miR-652, but decreased ARRB1. Overexpression of miR-29a/miR-652 prominently decreased Th17, IL-17A, IL-22 and ARRB1 in the normal CD4+ T cells. Both miR-29a and miR-652 targeted ARRB1 to regulate its expression. The effects of miR-29a/miR-652 overexpression on CD4+ T cells were reversed by ARRB1 overexpression. In vivo experiments demonstrated the protective role of miR-29a/miR-652 overexpression on liver fibrosis. Conclusion: ARRB1 mediated by miR-29a and miR-652 probably involved in the CD4+ T cells differentiation in patients with liver fibrosis, and functioned as a biomarker of fibrosis liver.
Key words: liver fibrosis, miR-29a, miR-652, ARRB1, CD4+ T cells
Stem cells from human exfoliated deciduous teeth (SHED) are isolated from the dental pulp tissue of primary teeth and can differentiate into neuronal cells. Although SHED are a desirable type of stem cells for transplantation therapy and for the study of neurological diseases, a large part of the neuronal differentiation machinery of SHED remains unclear. Recent studies have suggested that mitochondrial activity is involved in the differentiation of stem cells. In the present work, we investigated the neuronal differentiation machinery of SHED by focusing on mitochondrial activity. During neuronal differentiation of SHED, we observed increased mitochondrial membrane potential, increased mitochondrial DNA, and elongated mitochondria. Furthermore, to examine the demand for mitochondrial activity in neuronal differentiation, we then differentiated SHED into neuronal cells in the presence of rotenone, an inhibitor of mitochondrial respiratory chain complex I, and carbonyl cyanide m-chlorophenyl hydrazone (CCCP), a mitochondrial uncoupler, and found that neuronal differentiation was inhibited by treatment with rotenone and CCCP. These results indicated that increased mitochondrial activity was crucial for the neuronal differentiation of SHED.
Key words: mitochondria, differentiation, stem cells, dental pulp, exfoliated deciduous teeth
The dedicator of cytokinesis (DOCK) family proteins are known as one of guanine nucleotide exchange factors (GEFs), that contribute to cellular signaling processes by activating small G proteins. Although mammalian Zizimin is known to be a GEF for Cdc42 of Rho family small GTPase, its role in vivo is not well understood. Here we studied in vivo function of Drosophila Zizimin (Ziz). Knockdown of Ziz in eye imaginal discs induced the rough eye phenotype accompanied with fusion of ommatidia, loss of bristles and loss of pigments. Immunostaining analyses revealed that Ziz mainly localizes in the secondary pigment cells (SPCs) and tertiary pigment cells (TPCs) in pupal retinae. Ziz-knockdown induced SPC- and TPC-like cells with aberrant morphology in the pupal retina. Delta (Dl), a downstream target of EGFR signaling is known to regulate pigment cell differentiation. Loss-of-function mutation of Dl suppressed the rough eye phenotype and the defect in differentiation of SPCs and TPCs in Ziz-knockdown flies. Moreover, Ziz-knockdown increased Dl expression level especially in SPCs and TPCs. In addition, mutations of rhomboid-1 and roughoid that are activators of EGFR signaling pathway also suppressed both the rough eye phenotype and the defect in differentiation of SPCs and TPCs in Ziz-knockdown flies. Activation of EGFR signaling in Ziz-knockdown flies were further confirmed by immunostaining with anti-diphospho ERK IgG. These results indicate that Ziz negatively regulates the Dl expression in SPCs and TPCs to control differentiation of pigment cells and this regulation is mediated by EGFR signaling pathway.
Key words: Zizimin, DOCK, EGFR signaling pathway, pigment cell, Drosophila
Actin, a major component of microfilaments, is involved in various eukaryotic cellular functions. Over the past two decades, actin fused with fluorescent protein has been used as a probe to detect the organization and dynamics of the actin cytoskeleton in living eukaryotic cells. It is generally assumed that the expression of fusion protein of fluorescent protein does not disturb the distribution of endogenous actin throughout the cell, and that the distribution of the fusion protein reflects that of endogenous actin. However, we noticed that EGFP-β-actin caused the excessive formation of microfilaments in several mammalian cell lines. To investigate whether the position of the EGFP tag on actin affected the formation of filaments, we constructed an expression vector harboring a β-actin-EGFP gene. In contrast to EGFP-β-actin, cells expressing β-actin-EGFP showed actin filaments in a high background from the monomer actin in cytosol. Additionally, the detergent insoluble assay revealed that the majority of the detergent-insoluble cytoskeleton from cells expressing EGFP-β-actin was recovered in the pellet. Furthermore, we found that the expression of EGFP-β-actin affects the migration of NBT-L2b cells and the mechanical stiffness of U2OS cells. These results indicate that EGFP fused to the N-terminus of actin tend to form excessive actin filaments. In addition, EGFP-actin affects both the cellular morphological and physiological phenotypes as compared to actin-EGFP.
Key words: actin, GFP, cytoskeleton and probe
Deltamethrin (DM), a type II pyrethroid, robustly increases brain-derived neurotrophic factor (Bdnf) expression and has a neurotrophic effect in primary cultures of rat cortical neurons. In this study, we investigated the effect of DM on neurite morphology in cultured rat cortical neurons. DM significantly increased neurite outgrowth, but this increase was abolished when the BDNF scavenger tropomyosin receptor kinase B (TrkB)-Fc was added 10 min before the DM treatment. In contrast, the addition of TrkB-Fc 1 h after the treatment did not affect DM-induced neurite outgrowth. Our previous research has indicated that type II, but not type I, pyrethroids have the ability to induce Bdnf mRNA expression, but neither permethrin nor cypermethrin, which are type I and type II pyrethroids, respectively, affected neurite outgrowth in the current study. These results suggest that this effect is not due to increased Bdnf expression, and the effect is unique to DM. We previously demonstrated that calcineurin plays a role in the DM-mediated induction of Bdnf expression. However, the calcineurin inhibitor FK506 did not significantly affect DM-induced neurite outgrowth. DM-induced neurite outgrowth was abolished by U0126 and rapamycin, indicating the involvement of the mitogen-activated protein kinase (MAPK) and mammalian target of rapamycin (mTOR) pathways. Taken together, these findings suggest that DM activates endogenous BDNF/TrkB-mediated MAPK and mTOR pathways, thereby increasing neurite outgrowth.
Key words: BDNF, Deltamethrin, MAPK, mTOR, Neurite outgrowth
Bone marrow stromal cells, including endothelial cells and mesenchymal stromal cells, support the maintenance, differentiation, and retention of hematopoietic stem and precursor cells under steady state conditions. At the onset of an emergency, such as severe blood loss or infection, the status of hematopoiesis in the bone marrow changes rapidly to ensure efficient production of cells of specific lineages; however, the function of stromal cells in emergency hematopoiesis has not been fully elucidated. Here, we unexpectedly found that B precursor, mature B, and T cells were released from the bone marrow into the blood circulation in the early phase of hemorrhagic anemia and phenylhydrazine-induced hemolytic anemia. Administration of erythropoietin, which normally increases in response to anemia, stimulated the egress of IgDlow immature B cells and recirculating mature B cells, which usually reside in the perivascular and intravascular space, from the bone marrow within 24 h. We also observed that endothelial cells in the bone marrow expressed erythropoietin receptor, and the expression levels were higher than those in other tissues. Erythropoietin stimulation of bone marrow endothelial cells induced the phosphorylation of STAT5 in vitro. Moreover, in vivo treatment with erythropoietin decreased surface VCAM1 expression and Cxcl12 transcription in bone marrow endothelial cells, both of which are essential for immature and mature B cell retention in the bone marrow. These results suggest that bone marrow endothelial cells can sense and rapidly respond to erythropoietin increase during anemia, thereby regulating B cell emigration from the bone marrow during emergency hematopoiesis.
Key words: erythropoietin, anemia, endothelial cells, B cell, bone marrow microenvironment
The submandibular gland (SMG) is one of the major salivary glands that play important roles for variety of physiological functions, such as digestion of foods, prevention of infection, and lubrication of the mouth. Dysfunction of the SMG, often associated with a salivary inflammation, adversely influences a person’s quality of life. However, the mechanism underlying inflammation-driven dysfunction of the SMG is largely unknown. Here, we used a mouse model in which the main excretory duct of the SMG is ligated unilaterally to induce inflammation of the gland and examined the expression of Wnt5a, Ror1 and Ror2 genes, encoding Wnt5a ligand and its cognate receptors, which have been implicated in tissue damage or inflammatory responses in variety of tissues. We show that expression levels of Ror1, Ror2, and Wnt5a are increased in the ligated SMG undergoing interstitial fibrosis, which is accompanied by robust expression of fibrosis-associated genes, such as TGF-β1, TNF-α, IL-1β, and MMP-2. Increased immunostaining signal of Ror2 was detected in the fibrotic tissues with abundant accumulation of fibroblasts and collagen fibers in the ligated SMG, suggesting that Ror2-mediated signaling might be activated in response to tissue damage and associated with progression of fibrosis in the SMG.
Key words: submandibular gland, Ror2, Wnt5a, fibrosis, inflammation