scholarly journals A Novel Contact by a Novel Protein Complex Supports Cholesterol Transport to the Endoplasmic Reticulum

Contact ◽  
2018 ◽  
Vol 1 ◽  
pp. 251525641877968
Author(s):  
Akihiro Harada
Keyword(s):  
Endoplasmic Reticulum ◽  
Free Cholesterol ◽  
Membrane Lipids ◽  
Binding Protein ◽  
Cholesterol Transport ◽  
Transport Pathway ◽  
Hormone Synthesis ◽  
Novel Protein

Cholesterol is an essential component of membrane lipids and a starting material for hormone synthesis. After cholesterol is delivered to the cell as low-density lipoprotein, it is endocytosed and degraded in lysosomes to liberate free cholesterol. Free cholesterol is transported to the endoplasmic reticulum (ER) and esterified for further use. However, the mechanisms that transport cholesterol from lysosomes to the endoplasmic reticulum are poorly understood. We searched for binding proteins of a small GTP-binding protein, Rab11, and identified a novel protein, Rab11-binding protein containing LisH, coiled coil, and heat repeats (RELCH). RELCH also binds to oxysterol-binding protein (OSBP), an essential protein for nonvesicular cholesterol transport. The Rab11-RELCH-OSBP complex was found to tether to recycling endosomes and the trans-Golgi network, thereby mediating nonvesicular cholesterol transport between them. This pathway is distinct from the cholesterol transport pathway identified previously. In the absence of this complex, cholesterol accumulates in lysosomes in vitro and in vivo, suggesting the involvement of this complex in diseases associated with cholesterol transport.

scholarly journals Protection of pancreatic β-cells by exendin-4 may involve the reduction of endoplasmic reticulum stress; in vivo and in vitro studies

2007 ◽  
Vol 193 (1) ◽  
pp. 65-74 ◽  
Author(s):  
Shin Tsunekawa ◽  
Naoki Yamamoto ◽  
Katsura Tsukamoto ◽  
Yuji Itoh ◽  
Yukiko Kaneko ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Er Stress ◽  
Islet Cells ◽  
Binding Protein ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells

The aim of this study was to investigate the in vivo and in vitro effects of exendin-4, a potent glucagon-like peptide 1 agonist, on the protection of the pancreatic β-cells against their cell death. In in vivo experiments, we used β-cell-specific calmodulin-overexpressing mice where massive apoptosis takes place in their β-cells, and we examined the effects of chronic treatment with exendin-4. Chronic and s.c. administration of exendin-4 reduced hyperglycemia. The treatment caused significant increases of the insulin contents of the pancreas and islets, and retained the insulin-positive area. Dispersed transgenic islet cells lived only shortly, and several endoplasmic reticulum (ER) stress-related molecules such as immunoglobulin-binding protein (Bip), inositol-requiring enzyme-1α, X-box-binding protein-1 (XBP-1), RNA-activated protein kinase-like endoplasmic reticulum kinase, activating transcription factor-4, and C/EBP-homologous protein (CHOP) were more expressed in the transgenic islets. We also found that the spliced form of XBP-1, a marker of ER stress, was also increased in β-cell-specific calmodulin-overexpressing transgenic islets. In the quantitative real-time PCR analyses, the expression levels of Bip and CHOP were reduced in the islets from the transgenic mice treated with exendin-4. These findings suggest that excess of ER stress occurs in the transgenic β-cells, and the suppression of ER stress and resultant protection against cell death may be involved in the anti-diabetic effects of exendin-4.

scholarly journals Diesel Exhaust Particulates Induce Neutrophilic Lung Inflammation by Modulating Endoplasmic Reticulum Stress-Mediated CXCL1/KC Expression in Alveolar Macrophages

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 6046 ◽  
Author(s):  
Dong Im Kim ◽  
Mi-Kyung Song ◽  
Hye-In Kim ◽  
Kang Min Han ◽  
Kyuhong Lee
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Alveolar Macrophages ◽  
Diesel Exhaust ◽  
Lung Inflammation ◽  
Binding Protein ◽  
In Vitro Study ◽  
Vitro Study

Diesel exhaust particulates (DEP) have adverse effects on the respiratory system. Endoplasmic reticulum (ER) abnormalities contribute to lung inflammation. However, the relationship between DEP exposure and ER stress in the respiratory immune system and especially the alveolar macrophages (AM) is poorly understood. Here, we examined ER stress and inflammatory responses using both in vivo and in vitro study. For in vivo study, mice were intratracheally instilled with 25, 50, and 100 μg DEP and in vitro AM were stimulated with DEP at 1, 2, and 3 mg/mL. DEP increased lung weight and the number of inflammatory cells, especially neutrophils, and inflammatory cytokines in bronchoalveolar lavage fluid of mice. DEP also increased the number of DEP-pigmented AM and ER stress markers including bound immunoglobulin protein (BiP) and CCAAT/enhancer binding protein-homologous protein (CHOP) were upregulated in the lungs of DEP-treated mice. In an in vitro study, DEP caused cell damage, increased intracellular reactive oxygen species, and upregulated inflammatory genes and ER stress-related BiP, CHOP, splicing X-box binding protein 1, and activating transcription factor 4 expressions in AM. Furthermore, DEP released the C-X-C Motif Chemokine Ligand 1 (CXCL1/KC) in AM. In conclusion, DEP may contribute to neutrophilic lung inflammation pathogenesis by modulating ER stress-mediated CXCL1/KC expression in AM.

scholarly journals C4b-binding protein α-chain enhances antitumor immunity by facilitating the accumulation of tumor-infiltrating lymphocytes in the tumor microenvironment in pancreatic cancer

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Kosuke Sasaki ◽  
Shigetsugu Takano ◽  
Satoshi Tomizawa ◽  
Yoji Miyahara ◽  
Katsunori Furukawa ◽  
...  
Keyword(s):  
T Cell ◽  
Tumor Microenvironment ◽  
Binding Protein ◽  
Combined Treatment ◽  
Tumor Infiltrating Lymphocytes ◽  
Pdac Cell ◽  
Α Chain ◽  
Infiltrating Lymphocytes

Abstract Background Recent studies indicate that complement plays pivotal roles in promoting or suppressing cancer progression. We have previously identified C4b-binding protein α-chain (C4BPA) as a serum biomarker for the early detection of pancreatic ductal adenocarcinoma (PDAC). However, its mechanism of action remains unclear. Here, we elucidated the functional roles of C4BPA in PDAC cells and the tumor microenvironment. Methods We assessed stromal C4BPA, the C4BPA binding partner CD40, and the number of CD8+ tumor-infiltrating lymphocytes in resected human PDAC tissues via immunohistochemical staining. The biological functions of C4BPA were investigated in peripheral blood mononuclear cells (PBMCs) and human PDAC cell lines. Mouse C4BPA (mC4BPA) peptide, which is composed of 30 amino acids from the C-terminus and binds to CD40, was designed for further in vitro and in vivo experiments. In a preclinical experiment, we assessed the efficacy of gemcitabine plus nab-paclitaxel (GnP), dual immune checkpoint blockades (ICBs), and mC4BPA peptide in a mouse orthotopic transplantation model. Results Immunohistochemical analysis revealed that high stromal C4BPA and CD40 was associated with favorable PDAC prognosis (P=0.0005). Stromal C4BPA strongly correlated with the number of CD8+ tumor-infiltrating lymphocytes (P=0.001). In in vitro experiments, flow cytometry revealed that recombinant human C4BPA (rhC4BPA) stimulation increased CD4+ and CD8+ T cell numbers in PBMCs. rhC4BPA also promoted the proliferation of CD40-expressing PDAC cells. By contrast, combined treatment with gemcitabine and rhC4BPA increased PDAC cell apoptosis rate. mC4BPA peptide increased the number of murine T lymphocytes in vitro and the number of CD8+ tumor-infiltrating lymphocytes surrounding PDAC tumors in vivo. In a preclinical study, GnP/ICBs/mC4BPA peptide treatment, but not GnP treatment, led to the accumulation of a greater number of CD8+ T cells in the periphery of PDAC tumors and to greater tumor regression than did control treatment. Conclusions These findings demonstrate that the combination of GnP therapy with C4BPA inhibits PDAC progression by promoting antitumor T cell accumulation in the tumor microenvironment.

scholarly journals Dehydrodiisoeugenol inhibits colorectal cancer growth by endoplasmic reticulum stress-induced autophagic pathways

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Changhong Li ◽  
Kui Zhang ◽  
Guangzhao Pan ◽  
Haoyan Ji ◽  
Chongyang Li ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Endoplasmic Reticulum ◽  
Cell Growth ◽  
Er Stress ◽  
Cancer Cells ◽  
Tumor Xenograft ◽  
Anticancer Activities ◽  
Colorectal Cancer Cells

Abstract Background Dehydrodiisoeugenol (DEH), a novel lignan component extracted from nutmeg, which is the seed of Myristica fragrans Houtt, displays noticeable anti-inflammatory and anti-allergic effects in digestive system diseases. However, the mechanism of its anticancer activity in gastrointestinal cancer remains to be investigated. Methods In this study, the anticancer effect of DEH on human colorectal cancer and its underlying mechanism were evaluated. Assays including MTT, EdU, Plate clone formation, Soft agar, Flow cytometry, Electron microscopy, Immunofluorescence and Western blotting were used in vitro. The CDX and PDX tumor xenograft models were used in vivo. Results Our findings indicated that treatment with DEH arrested the cell cycle of colorectal cancer cells at the G1/S phase, leading to significant inhibition in cell growth. Moreover, DEH induced strong cellular autophagy, which could be inhibited through autophagic inhibitors, with a rction in the DEH-induced inhibition of cell growth in colorectal cancer cells. Further analysis indicated that DEH also induced endoplasmic reticulum (ER) stress and subsequently stimulated autophagy through the activation of PERK/eIF2α and IRE1α/XBP-1 s/CHOP pathways. Knockdown of PERK or IRE1α significantly decreased DEH-induced autophagy and retrieved cell viability in cells treated with DEH. Furthermore, DEH also exhibited significant anticancer activities in the CDX- and PDX-models. Conclusions Collectively, our studies strongly suggest that DEH might be a potential anticancer agent against colorectal cancer by activating ER stress-induced inhibition of autophagy.

scholarly journals Monocyte tissue factor induction by lipopolysaccharide (LPS): dependence on LPS-binding protein and CD14, and inhibition by a recombinant fragment of bactericidal/permeability-increasing protein

Blood ◽  
1994 ◽  
Vol 83 (9) ◽  
pp. 2516-2525 ◽  
Author(s):  
K Meszaros ◽  
S Aberle ◽  
R Dedrick ◽  
R Machovich ◽  
A Horwitz ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Mononuclear Cells ◽  
Human Peripheral Blood ◽  
Binding Protein ◽  
Mononuclear Phagocytes ◽  
Factor Vii ◽  
Peripheral Blood Mononuclear ◽  
Recombinant Fragment

Abstract Mononuclear phagocytes, stimulated by bacterial lipopolysaccharide (LPS), have been implicated in the activation of coagulation in sepsis and endotoxemia. In monocytes LPS induces the synthesis of tissue factor (TF) which, assembled with factor VII, initiates the blood coagulation cascades. In this study we investigated the mechanism of LPS recognition by monocytes, and the consequent expression of TF mRNA and TF activity. We also studied the inhibition of these effects of LPS by rBPI23, a 23-kD recombinant fragment of bactericidal/permeability increasing protein, which has been shown to antagonize LPS in vitro and in vivo. Human peripheral blood mononuclear cells, or monocytes isolated by adherence, were stimulated with Escherichia coli O113 LPS at physiologically relevant concentrations (> or = 10 pg/mL). The effect of LPS was dependent on the presence of the serum protein LBP (lipopolysaccharide-binding protein), as shown by the potentiating effect of human recombinant LBP or serum. Furthermore, recognition of low amounts of LPS by monocytes was also dependent on CD14 receptors, because monoclonal antibodies against CD14 greatly reduced the LPS sensitivity of monocytes in the presence of serum or rLBP. Induction of TF activity and mRNA expression by LPS were inhibited by rBPI23. The expression of tumor necrosis factor showed qualitatively similar changes. Considering the involvement of LPS-induced TF in the potentially lethal intravascular coagulation in sepsis, inhibition of TF induction by rBPI23 may be of therapeutic benefit.

scholarly journals In vitro and in vivo evidence for actin association of the naphthylphthalamic acid-binding protein from zucchini hypocotyls

1998 ◽  
Vol 13 (3) ◽  
pp. 291-301 ◽  
Author(s):  
John H. Butler ◽  
Shiquan Hu ◽  
Shari R. Brady ◽  
Michael W. Dixon ◽  
Gloria K. Muday
Keyword(s):  
Binding Protein ◽  
Acid Binding Protein ◽  
Naphthylphthalamic Acid

scholarly journals Tethering DNA Damage Checkpoint Mediator Proteins Topoisomerase IIβ-binding Protein 1 (TopBP1) and Claspin to DNA Activates Ataxia-Telangiectasia Mutated and RAD3-related (ATR) Phosphorylation of Checkpoint Kinase 1 (Chk1)

2011 ◽  
Vol 286 (22) ◽  
pp. 19229-19236 ◽  
Author(s):  
Laura A. Lindsey-Boltz ◽  
Aziz Sancar
Keyword(s):  
Dna Damage ◽  
Ataxia Telangiectasia ◽  
Mammalian Cells ◽  
Binding Protein ◽  
Effector Proteins ◽  
Ataxia Telangiectasia Mutated ◽  
Checkpoint Kinase ◽  
Atr Kinase

The ataxia-telangiectasia mutated and RAD3-related (ATR) kinase initiates DNA damage signaling pathways in human cells after DNA damage such as that induced upon exposure to ultraviolet light by phosphorylating many effector proteins including the checkpoint kinase Chk1. The conventional view of ATR activation involves a universal signal consisting of genomic regions of replication protein A-covered single-stranded DNA. However, there are some indications that the ATR-mediated checkpoint can be activated by other mechanisms. Here, using the well defined Escherichia coli lac repressor/operator system, we have found that directly tethering the ATR activator topoisomerase IIβ-binding protein 1 (TopBP1) to DNA is sufficient to induce ATR phosphorylation of Chk1 in an in vitro system as well as in vivo in mammalian cells. In addition, we find synergistic activation of ATR phosphorylation of Chk1 when the mediator protein Claspin is also tethered to the DNA with TopBP1. Together, these findings indicate that crowding of checkpoint mediator proteins on DNA is sufficient to activate the ATR kinase.

scholarly journals Overexpression of CALNUC (Nucleobindin) Increases Agonist and Thapsigargin Releasable Ca2+ Storage in the Golgi

1999 ◽  
Vol 145 (2) ◽  
pp. 279-289 ◽  
Author(s):  
Ping Lin ◽  
Yong Yao ◽  
Robert Hofmeister ◽  
Roger Y. Tsien ◽  
Marilyn Gist Farquhar
Keyword(s):  
Endoplasmic Reticulum ◽  
Cho Cells ◽  
Binding Capacity ◽  
Binding Protein ◽  
Ip3 Receptor ◽  
Transfected Cells ◽  
Permeabilized Cells ◽  
Endoplasmic Reticulum Calcium ◽  
Golgi Protein

We previously demonstrated that CALNUC, a Ca2+-binding protein with two EF-hands, is the major Ca2+-binding protein in the Golgi by 45Ca2+ overlay (Lin, P., H. Le-Niculescu, R. Hofmeister, J.M. McCaffery, M. Jin, H. Henneman, T. McQuistan, L. De Vries, and M. Farquhar. 1998. J. Cell Biol. 141:1515–1527). In this study we investigated CALNUC's properties and the Golgi Ca2+ storage pool in vivo. CALNUC was found to be a highly abundant Golgi protein (3.8 μg CALNUC/mg Golgi protein, 2.5 × 105 CALNUC molecules/NRK cell) and to have a single high affinity, low capacity Ca2+-binding site (Kd = 6.6 μM, binding capacity = 1.1 μmol Ca2+/μmol CALNUC). 45Ca2+ storage was increased by 2.5- and 3-fold, respectively, in HeLa cells transiently overexpressing CALNUC-GFP and in EcR-CHO cells stably overexpressing CALNUC. Deletion of the first EF-hand α helix from CALNUC completely abolished its Ca2+-binding capability. CALNUC was correctly targeted to the Golgi in transfected cells as it colocalized and cosedimented with the Golgi marker, α-mannosidase II (Man II). Approximately 70% of the 45Ca2+ taken up by HeLa and CHO cells overexpressing CALNUC was released by treatment with thapsigargin, a sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) (Ca2+ pump) blocker. Stimulation of transfected cells with the agonist ATP or IP3 alone (permeabilized cells) also resulted in a significant increase in Ca2+ release from Golgi stores. By immunofluorescence, the IP3 receptor type 1 (IP3R-1) was distributed over the endoplasmic reticulum and codistributed with CALNUC in the Golgi. These results provide direct evidence that CALNUC binds Ca2+ in vivo and together with SERCA and IP3R is involved in establishment of the agonist-mobilizable Golgi Ca2+ store.

Sign in / Sign up

Export Citation Format

Share Document