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There are 47 results for Insulin (displaying 21 to 30).

Cardiac‐specific succinate dehydrogenase deficiency in Barth syndrome

Barth syndrome ( BTHS ) is a cardiomyopathy caused by the loss of tafazzin, a mitochondrial acyltransferase involved in the maturation of the glycerophospholipid cardiolipin. It has remained enigmatic as to why a systemic loss of cardiolipin leads to cardiomyopathy. Using a genetic ablation of tafazzin function in the BTHS mouse model, we identified severe structural changes in respiratory chain supercomplexes at a pre‐onset stage of the disease. This reorganization of supercomplexes was specific to cardiac tissue and could be recapitulated in cardiomyocytes derived from BTHS patients. Moreover, our analyses demonstrate a cardiac‐specific loss of succinate dehydrogenase ( SDH ), an enzyme linking the respiratory chain with the tricarboxylic acid cycle. As a similar defect of SDH is apparent in patient cell‐derived cardiomyocytes, we conclude that these defects represent a molecular basis for the cardiac pathology in Barth syndrome.

… into cardiomyocytes was performed by following the protocol as described previously (Lian et al , ). Briefly, undifferentiated iPSCs in feeder‐free system were cultured until confluent. To induce cardiac differentiation, the medium was replaced with RPMI + B27‐insulin medium, which contained RPMI 1640 medium (Life Technologies) supplemented with 2 mM l ‐glutamine and B27 without insulin (Life Technologies). The GSK3 inhibitor CHIR99021 (10 μM, Millipore) was added to the culture for 24 h. Subsequently …

Jan Dudek et al. EMBO molecular medicine February 2016

ATG1, an autophagy regulator, inhibits cell growth by negatively regulating S6 kinase

It has been proposed that cell growth and autophagy are coordinated in response to cellular nutrient status, but the relationship between them is not fully understood. Here, we have characterized the fly mutants of Autophagy‐specific gene 1 ( ATG1 ), an autophagy‐regulating kinase, and found that ATG1 is a negative regulator of the target of rapamycin (TOR)/S6 kinase (S6K) pathway. Our Drosophila studies have shown that ATG1 inhibits TOR/S6K‐dependent cell growth and development by interfering with S6K activation. Consistently, overexpression of ATG1 in mammalian cells also markedly inhibits S6K in a kinase activity‐dependent manner, and short interfering RNA‐mediated knockdown of ATG1 induces ectopic activation of S6K and S6 phosphorylation. Moreover, we demonstrated that ATG1 specifically inhibits S6K activity by blocking phosphorylation of S6K at Thr 389. Taken together, our genetic and biochemical results strongly indicate crosstalk between autophagy and cell growth regulation.

… the family members in different species. Therefore, we examined whether ATG1α also affects the phosphorylation of Akt and RSK. Interestingly, the phosphorylation of Akt and RSK was not affected by ATG1α, with or without stimulation by insulin and EGF ( , respectively). These data indicate that ATG1α specifically modulates S6K activity. Next, to understand the molecular mechanism of the specific regulation of S6K by ATG1, we investigated whether ATG1 affects the phosphorylation of Thr 229 in S6K …

Sung Bae Lee et al. EMBO Reports April 2007

Mitochondrial fission and remodelling contributes to muscle atrophy

Mitochondria are crucial organelles in the production of energy and in the control of signalling cascades. A machinery of pro‐fusion and fission proteins regulates their morphology and subcellular localization. In muscle this results in an orderly pattern of intermyofibrillar and subsarcolemmal mitochondria. Muscular atrophy is a genetically controlled process involving the activation of the autophagy‐lysosome and the ubiquitin–proteasome systems. Whether and how the mitochondria are involved in muscular atrophy is unknown. Here, we show that the mitochondria are removed through autophagy system and that changes in mitochondrial network occur in atrophying muscles. Expression of the fission machinery is per se sufficient to cause muscle wasting in adult animals, by triggering organelle dysfunction and AMPK activation. Conversely, inhibition of the mitochondrial fission inhibits muscle loss during fasting and after FoxO3 overexpression. Mitochondrial‐dependent muscle atrophy requires AMPK activation as inhibition of AMPK restores muscle size in myofibres with altered mitochondria. Thus, disruption of the mitochondrial network is an essential amplificatory loop of the muscular atrophy programme.

… regulates autophagy through Bnip3 ( ). Inhibition of Bnip3 greatly reduces autophagosome formation in skeletal muscles even in presence of activated FoxO3 ( ; ). Bnip3 belongs to BH3‐only proteins of bcl2 family and can induce apoptosis as well as mitochondrial fragmentation and mitophagy ( ). The autophagy‐lysosome system controls morphology and function of organelles. Alterations in the content, shape or function of the mitochondria have been related with muscle wasting. For instance, insulin

Vanina Romanello et al. The EMBO Journal May 2010

Red1 promotes the elimination of meiosis‐specific mRNAs in vegetatively growing fission yeast

Meiosis‐specific mRNAs are transcribed in vegetative fission yeast, and these meiotic mRNAs are selectively removed from mitotic cells to suppress meiosis. This RNA elimination system requires degradation signal sequences called determinant of selective removal (DSR), an RNA‐binding protein Mmi1, polyadenylation factors, and the nuclear exosome. However, the detailed mechanism by which meiotic mRNAs are selectively degraded in mitosis but not meiosis is not understood fully. Here we report that Red1, a novel protein, is essential for elimination of meiotic mRNAs from mitotic cells. A red1 deletion results in the accumulation of a large number of meiotic mRNAs in mitotic cells. Red1 interacts with Mmi1, Pla1, the canonical poly(A) polymerase, and Rrp6, a subunit of the nuclear exosome, and promotes the destabilization of DSR‐containing mRNAs. Moreover, Red1 forms nuclear bodies in mitotic cells, and these foci are disassembled during meiosis. These results demonstrate that Red1 is involved in DSR‐directed RNA decay to prevent ectopic expression of meiotic mRNAs in vegetative cells.

… in other organisms. Indeed, a similar phenomenon, termed soma‐to‐germline transformation, has been reported in Caenorhabditis elegans . In the worm, germline‐specific genes are transcriptionally repressed by the Mi‐2 complex, composed of MEP‐1, LET‐418, and HDA‐1, and by factors involved in the Rb pathway including LIN‐36, HPL‐1, and DPL‐1 ( ; ). A recent report has also demonstrated that insulin‐like signaling mutants such as daf‐2 and age‐1 express germline genes in somatic cells …

Tomoyasu Sugiyama et al. The EMBO Journal March 2011

Mfn2 modulates the UPR and mitochondrial function via repression of PERK

Mitofusin 2 (Mfn2) is a key protein in mitochondrial fusion and it participates in the bridging of mitochondria to the endoplasmic reticulum (ER). Recent data indicate that Mfn2 ablation leads to ER stress. Here we report on the mechanisms by which Mfn2 modulates cellular responses to ER stress. Induction of ER stress in Mfn2‐deficient cells caused massive ER expansion and excessive activation of all three Unfolded Protein Response (UPR) branches (PERK, XBP‐1, and ATF6). In spite of an enhanced UPR, these cells showed reduced activation of apoptosis and autophagy during ER stress. Silencing of PERK increased the apoptosis of Mfn2‐ablated cells in response to ER stress. XBP‐1 loss‐of‐function ameliorated autophagic activity of these cells upon ER stress. Mfn2 physically interacts with PERK, and Mfn2‐ablated cells showed sustained activation of this protein kinase under basal conditions. Unexpectedly, PERK silencing in these cells reduced ROS production, normalized mitochondrial calcium, and improved mitochondrial morphology. In summary, our data indicate that Mfn2 is an upstream modulator of PERK. Furthermore, Mfn2 loss‐of‐function reveals that PERK is a key regulator of mitochondrial morphology and function.

… in the outer mitochondrial membrane and in mitochondrial‐associated membranes. In addition to controlling ER morphology, this protein participates in mitochondrial fusion and regulates the transfer of calcium from the ER to mitochondria ( ; ; ; ; ). Moreover, Mfn2 deficiency upregulates markers of the UPR in liver, skeletal muscle, and cultured cells ( ; ), and normalization of ER stress by treatment with tauroursodeoxycholic acid ameliorates deficient insulin signalling in liver‐specific Mfn2 …

Juan Pablo Muñoz et al. The EMBO Journal August 2013

CPAP promotes timely cilium disassembly to maintain neural progenitor pool

A mutation in the centrosomal‐P4.1‐associated protein ( CPAP ) causes Seckel syndrome with microcephaly, which is suggested to arise from a decline in neural progenitor cells ( NPC s) during development. However, mechanisms of NPC s maintenance remain unclear. Here, we report an unexpected role for the cilium in NPC s maintenance and identify CPAP as a negative regulator of ciliary length independent of its role in centrosome biogenesis. At the onset of cilium disassembly, CPAP provides a scaffold for the cilium disassembly complex ( CDC ), which includes Nde1, Aurora A, and OFD 1, recruited to the ciliary base for timely cilium disassembly. In contrast, mutated CPAP fails to localize at the ciliary base associated with inefficient CDC recruitment, long cilia, retarded cilium disassembly, and delayed cell cycle re‐entry leading to premature differentiation of patient iPS ‐derived NPC s. Aberrant CDC function also promotes premature differentiation of NPC s in Seckel iPS ‐derived organoids. Thus, our results suggest a role for cilia in microcephaly and its involvement during neurogenesis and brain size control.

… ) and pluripotent markers staining. Human iPS cells were grown in serum‐containing medium for 6 days, detached by accutase treatment, and then replated on collagen type I‐coated dishes. Endodermal differentiation was induced by low‐serum‐containing medium supplemented with HGF, Oncostatin M, and 100 nM dexamethasone for 10 days. Mesodermal differentiation was induced by serum‐free medium containing insulin and 10 μM SB431542 for 20 days. Similar amounts of feeder‐free human WT or patient iPS …

Elke Gabriel et al. The EMBO Journal April 2016

PTPRN2 and PLCβ1 promote metastatic breast cancer cell migration through PI(4,5)P2‐dependent actin remodeling

Altered abundance of phosphatidyl inositides ( PI s) is a feature of cancer. Various PI s mark the identity of diverse membranes in normal and malignant cells. Phosphatidylinositol 4,5‐bisphosphate ( PI (4,5)P 2 ) resides predominantly in the plasma membrane, where it regulates cellular processes by recruiting, activating, or inhibiting proteins at the plasma membrane. We find that PTPRN 2 and PLC β1 enzymatically reduce plasma membrane PI (4,5)P 2 levels in metastatic breast cancer cells through two independent mechanisms. These genes are upregulated in highly metastatic breast cancer cells, and their increased expression associates with human metastatic relapse. Reduction in plasma membrane PI (4,5)P 2 abundance by these enzymes releases the PI (4,5)P 2 ‐binding protein cofilin from its inactive membrane‐associated state into the cytoplasm where it mediates actin turnover dynamics, thereby enhancing cellular migration and metastatic capacity. Our findings reveal an enzymatic network that regulates metastatic cell migration through lipid‐dependent sequestration of an actin‐remodeling factor.

… , PTPRN2 has been implicated in insulin and neurotransmitter exocytosis; however, the precise role of PTPRN2 in the secretory pathway is unknown (Cai et al , ). PTPRN2 belongs to the protein tyrosine phosphatase family, but does not exhibit activity against phosphoprotein substrates due to several critical amino acid variations in the PTP domain (Magistrelli et al , ). Recently, PTPRN2 was found to exhibit phosphatidylinositol phosphatase (PIP) activity against PI(4,5)P 2 and, to a lesser extent …

Caitlin A Sengelaub et al. The EMBO Journal January 2016

Transcriptional co‐factor Transducin beta‐like (TBL) 1 acts as a checkpoint in pancreatic cancer malignancy

Pancreatic ductal adenocarcinoma ( PDAC ) is the fourth leading cause of cancer fatalities in Western societies, characterized by high metastatic potential and resistance to chemotherapy. Critical molecular mechanisms of these phenotypical features still remain unknown, thus hampering the development of effective prognostic and therapeutic measures in PDAC . Here, we show that transcriptional co‐factor Transducin beta‐like ( TBL ) 1 was over‐expressed in both human and murine PDAC . Inactivation of TBL 1 in human and mouse pancreatic cancer cells reduced cellular proliferation and invasiveness, correlating with diminished glucose uptake, glycolytic flux, and oncogenic PI 3 kinase signaling which in turn could rescue TBL 1 deficiency‐dependent phenotypes. TBL 1 deficiency both prevented and reversed pancreatic tumor growth, mediated transcriptional PI 3 kinase inhibition, and increased chemosensitivity of PDAC cells in vivo . As TBL 1 mRNA levels were also found to correlate with PI 3 kinase levels and overall survival in a cohort of human PDAC patients, TBL 1 was identified as a checkpoint in the malignant behavior of pancreatic cancer and its expression may serve as a novel molecular target in the treatment of human PDAC .

… the possibility that also in pancreatic tumor cells, TBL1 may act downstream of hormonal signal transduction, including cAMP and insulin (Stoy, Strobel and Herzig, unpublished). It will be interesting to determine whether and how these endocrine cues interact with the mutant KRAS pathway to induce TBL1 gene transcription in the PDAC setting. TBL1 was originally cloned in relationship to an X‐linked human disorder, Ocular Albinism with late‐onset Sensorineural Deafness (OASD), in which deletion …

Christian Stoy et al. EMBO molecular medicine August 2015

Autophagy‐based unconventional secretory pathway for extracellular delivery of IL‐1β

Autophagy controls the quality and quantity of the eukaryotic cytoplasm while performing two evolutionarily highly conserved functions: cell‐autonomous provision of energy and nutrients by cytosol autodigestion during starvation, and removal of defunct organelles and large aggregates exceeding the capacity of other cellular degradative systems. In contrast to these autodigestive processes, autophagy in yeast has additional, biogenesis functions. However, no equivalent biosynthetic roles have been described for autophagy in mammals. Here, we show that in mammalian cells, autophagy has a hitherto unappreciated positive contribution to the biogenesis and secretion of the proinflammatory cytokine IL‐1β via an export pathway that depends on Atg5, inflammasome, at least one of the two mammalian Golgi reassembly stacking protein (GRASP) paralogues, GRASP55 (GORASP2) and Rab8a. This process, which is a type of unconventional secretion, expands the functional manifestations of autophagy beyond autodigestive and quality control roles in mammals. It enables a subset of cytosolic proteins devoid of signal peptide sequences, and thus unable to access the conventional pathway through the ER, to enter an autophagy‐based secretory pathway facilitating their exit from the cytoplasm.

… where LC3 and IL‐1β colocalized. We observed an overlap between the LC3 + IL‐1β + profiles and Rab8a ( ). Rab8a is a regulator of polarized membrane trafficking, constitutive biosynthetic trafficking, and plasma membrane fusion of insulin‐responsive ( ) and other vesicular carriers ( ; ; ; ). Rab8a also colocalized with LC3 and IL‐1β in cells exposed to nigericin ( ). Rab8a was required for enhanced IL‐1β secretion caused by starvation‐induced autophagy and inflammasome activation …

Nicolas Dupont et al. The EMBO Journal November 2011

Antithetical NFATc1–Sox2 and p53–miR200 signaling networks govern pancreatic cancer cell plasticity

In adaptation to oncogenic signals, pancreatic ductal adenocarcinoma ( PDAC ) cells undergo epithelial–mesenchymal transition ( EMT ), a process combining tumor cell dedifferentiation with acquisition of stemness features. However, the mechanisms linking oncogene‐induced signaling pathways with EMT and stemness remain largely elusive. Here, we uncover the inflammation‐induced transcription factor NFAT c1 as a central regulator of pancreatic cancer cell plasticity. In particular, we show that NFAT c1 drives EMT reprogramming and maintains pancreatic cancer cells in a stem cell‐like state through Sox2‐dependent transcription of EMT  and stemness factors. Intriguingly, NFAT c1–Sox2 complex‐mediated PDAC dedifferentiation and progression is opposed by antithetical p53‐miR200c signaling, and inactivation of the tumor suppressor pathway is essential for tumor dedifferentiation and dissemination both in genetically engineered mouse models ( GEMM ) and human PDAC . Based on these findings, we propose the existence of a hierarchical signaling network regulating PDAC cell plasticity and suggest that the molecular decision between epithelial cell preservation and conversion into a dedifferentiated cancer stem cell‐like phenotype depends on opposing levels of p53 and NFAT c1 signaling activities.

… were performed as described previously (Baumgart et al , ). All data obtained from microarray analysis were deposited (MIAME, accession number: E‐MTAB‐2324). For sphere‐formation assay, adherent pancreatic tumor cells were dissociated to single cells by 0.05% trypsin–EDTA solution (Life Technologies) and plated at 100,000 cells per ml in serum‐free DMEM containing insulin (Life Technologies), Albumin Bovine Fraction V (Sigma), N‐2 Plus media, B‐27 (Life Technologies), EGF (Sigma), and HB‐EGF …

Shiv K Singh et al. The EMBO Journal February 2015
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