scholarly journals Neuroprogenitor Cells From Patients With TBCK Encephalopathy Suggest Deregulation of Early Secretory Vesicle Transport

2022 ◽  
Vol 15 ◽  
Author(s):  
Danielle de Paula Moreira ◽  
Angela May Suzuki ◽  
André Luiz Teles e Silva ◽  
Elisa Varella-Branco ◽  
Maria Cecília Zorél Meneghetti ◽  
...  
Keyword(s):  
Cell Cycle Progression ◽  
Secretory Pathway ◽  
Molecular Mechanisms ◽  
Secretory Vesicle ◽  
Psychomotor Retardation ◽  
Vesicle Transport ◽  
Early Secretory Pathway ◽  
Pathogenic Variants ◽  
Altered Cell ◽  
Induced Pluripotent

Biallelic pathogenic variants in TBCK cause encephaloneuropathy, infantile hypotonia with psychomotor retardation, and characteristic facies 3 (IHPRF3). The molecular mechanisms underlying its neuronal phenotype are largely unexplored. In this study, we reported two sisters, who harbored biallelic variants in TBCK and met diagnostic criteria for IHPRF3. We provided evidence that TBCK may play an important role in the early secretory pathway in neuroprogenitor cells (iNPC) differentiated from induced pluripotent stem cells (iPSC). Lack of functional TBCK protein in iNPC is associated with impaired endoplasmic reticulum-to-Golgi vesicle transport and autophagosome biogenesis, as well as altered cell cycle progression and severe impairment in the capacity of migration. Alteration in these processes, which are crucial for neurogenesis, neuronal migration, and cytoarchitecture organization, may represent an important causative mechanism of both neurodevelopmental and neurodegenerative phenotypes observed in IHPRF3. Whether reduced mechanistic target of rapamycin (mTOR) signaling is secondary to impaired TBCK function over other secretory transport regulators still needs further investigation.

Peroxisomal membrane proteins are properly targeted to peroxisomes in the absence of COPI- and COPII-mediated vesicular transport

2001 ◽  
Vol 114 (11) ◽  
pp. 2199-2204 ◽  
Author(s):  
Tineke Voorn-Brouwer ◽  
Astrid Kragt ◽  
Henk F. Tabak ◽  
Ben Distel
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Proteins ◽  
Secretory Pathway ◽  
Human Fibroblasts ◽  
Vesicle Transport ◽  
Peroxisome Biogenesis ◽  
Peroxisomal Membrane ◽  
Classic Model ◽  
Early Secretory Pathway

The classic model for peroxisome biogenesis states that new peroxisomes arise by the fission of pre-existing ones and that peroxisomal matrix and membrane proteins are recruited directly from the cytosol. Recent studies challenge this model and suggest that some peroxisomal membrane proteins might traffic via the endoplasmic reticulum to peroxisomes. We have studied the trafficking in human fibroblasts of three peroxisomal membrane proteins, Pex2p, Pex3p and Pex16p, all of which have been suggested to transit the endoplasmic reticulum before arriving in peroxisomes. Here, we show that targeting of these peroxisomal membrane proteins is not affected by inhibitors of COPI and COPII that block vesicle transport in the early secretory pathway. Moreover, we have obtained no evidence for the presence of these peroxisomal membrane proteins in compartments other than peroxisomes and demonstrate that COPI and COPII inhibitors do not affect peroxisome morphology or integrity. Together, these data fail to provide any evidence for a role of the endoplasmic reticulum in peroxisome biogenesis.

scholarly journals Profiling the microRNA Expression in Human iPS and iPS-derived Retinal Pigment Epithelium

2014 ◽  
Vol 13s5 ◽  
pp. CIN.S14074 ◽  
Author(s):  
Heuy-Ching Wang ◽  
Whitney A. Greene ◽  
Ramesh R. Kaini ◽  
Jane Shen-Gunther ◽  
Hung-I H Chen ◽  
...  
Keyword(s):  
Retinal Pigment Epithelium ◽  
Mirna Expression ◽  
Cell Cycle Progression ◽  
Molecular Mechanisms ◽  
Expression Profiles ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Ips Cells ◽  
Differentially Expressed ◽  
Induced Pluripotent

The purpose of this study is to characterize the microRNA (miRNA) expression profiles of induced pluripotent stem (iPS) cells and retinal pigment epithelium (RPE) derived from induced pluripotent stem cells (iPS-RPE). MiRNAs have been demonstrated to play critical roles in both maintaining pluripotency and facilitating differentiation. Gene expression networks accountable for maintenance and induction of pluripotency are linked and share components with those networks implicated in oncogenesis. Therefore, we hypothesize that miRNA expression profiling will distinguish iPS cells from their iPS-RPE progeny. To identify and analyze differentially expressed miRNAs, RPE was derived from iPS using a spontaneous differentiation method. MiRNA microarray analysis identified 155 probes that were statistically differentially expressed between iPS and iPS-RPE cells. Up-regulated miRNAs including miR-181c and miR-129–5p may play a role in promoting differentiation, while down-regulated miRNAs such as miR-367, miR-18b, and miR-20b are implicated in cell proliferation. Subsequent miRNA-target and network analysis revealed that these miRNAs are involved in cellular development, cell cycle progression, cell death, and survival. A systematic interrogation of temporal and spatial expression of iPS-RPE miRNAs and their associated target mRNAs will provide new insights into the molecular mechanisms of carcinogenesis, eye differentiation and development.

ID: 90: ADAM10 REGULATES STEMNESS OF ADULT NEURAL STEM CELLS BY MEDIATING THEIR POSITIONING WITHIN THE SVZ NICHE

2016 ◽  
Vol 64 (4) ◽  
pp. 944.1-944
Author(s):  
N McMillan
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Molecular Mechanisms ◽  
Conditional Knockout ◽  
Cycle Progression ◽  
Extrinsic Cues ◽  
Brdu Label ◽  
Affect Cell Cycle Progression ◽  
Altered Cell ◽  
A Disintegrin And Metalloproteinase

The subventricular zone (SVZ) niche has been defined to have two distinct microenivroments, an apical compartment that is directly in contact with CSF and a basal compartment with a rich vascular network. Both these compartments regulate neural stem cell (NSC) properties via a diverse array of extrinsic cues by regulating both NSC-NSC and NSC-niche interactions. A majority of these signaling mechanisms are initiated by metalloproteinases. In this study, we investigated one such molecule, a disintegrin and metalloproteinase 10 (ADAM10) and its role in maintaining NSC properties. Using a conditional knockout, in which ADAM10 is specifically deleted in NSCs and NPCs (Nestin-CRE™/ADAM10fl/fl; denoted as KO) we noted altered contacts within the apical and basal compartments. BrdU pulse-chase studies demonstrated an increased number of long-term retaining BrdU NSCs in these KO mice. We also observed decreased BrdU label retaining neurons in the olfactory bulb in addition to a decreased neuroblast population in the SVZ indicating impaired neurogenesis in the KO mice. Intriguingly, we also observed cytoskeletal changes in NSCs and decreased migration of cells from the core of neurospheres derived from KO SVZ cells. This altered cell shape could intrinsically affect cell cycle progression. Taken together, this data suggests ADAM10 activity within the SVZ niche regulates NSC intrinsic properties and alters their cell cycle progression. Moreover, ADAM10 deletion appears to promote an aberrant self-renewal phenotype in NSCs preventing their differentiation. A more thorough understanding of how ADAM10 mediates these cellular changes and the underlying molecular mechanisms could be crucial in enhancing SVZ neurogenesis.

scholarly journals Tissue Nonspecific Alkaline Phosphatase Is Activated via a Two-step Mechanism by Zinc Transport Complexes in the Early Secretory Pathway

2011 ◽  
Vol 286 (18) ◽  
pp. 16363-16373 ◽  
Author(s):  
Ayako Fukunaka ◽  
Yayoi Kurokawa ◽  
Fumie Teranishi ◽  
Israel Sekler ◽  
Kimimitsu Oda ◽  
...  
Keyword(s):  
Alkaline Phosphatase ◽  
Secretory Pathway ◽  
Molecular Mechanisms ◽  
Zinc Content ◽  
Protein Stabilization ◽  
Zinc Transport ◽  
Early Secretory Pathway ◽  
Tissue Nonspecific Alkaline Phosphatase ◽  
Dt40 Cells ◽  
Step Mechanism

A number of enzymes become functional by binding to zinc during their journey through the early secretory pathway. The zinc transporters (ZnTs) located there play important roles in this step. We have previously shown that two zinc transport complexes, ZnT5/ZnT6 heterodimers and ZnT7 homo-oligomers, are required for the activation of alkaline phosphatases, by converting them from the apo- to the holo-form. Here, we investigated the molecular mechanisms of this activation. ZnT1 and ZnT4 expressed in chicken DT40 cells did not contribute to the activation of tissue nonspecific alkaline phosphatase (TNAP). The reduced activity of TNAP in DT40 cells deficient in both ZnT complexes was not restored by zinc supplementation nor by exogenous expression of other ZnTs that increase the zinc content in the secretory pathway. Moreover, we showed that expression of ZnT5/ZnT6 heterodimers reconstituted with zinc transport-incompetent ZnT5 mutant failed to restore TNAP activity but could stabilize the TNAP protein as the apo-form, regardless of zinc status. These findings demonstrate that TNAP is activated not simply by passive zinc binding but by an elaborate two-step mechanism via protein stabilization followed by enzyme conversion from the apo- to the holo-form with zinc loaded by ZnT complexes in the early secretory pathway.

scholarly journals Detailed analyses of the crucial functions of Zn transporter proteins in alkaline phosphatase activation

2020 ◽  
Vol 295 (17) ◽  
pp. 5669-5684 ◽  
Author(s):  
Eisuke Suzuki ◽  
Namino Ogawa ◽  
Taka-aki Takeda ◽  
Yukina Nishito ◽  
Yu-ki Tanaka ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Molecular Mechanisms ◽  
Genetically Engineered ◽  
Minor Role ◽  
Activation Process ◽  
Early Secretory Pathway ◽  
Zip Transporters ◽  
A Minor ◽  
Phosphatase Activation ◽  
Dt40 Cells

Numerous zinc ectoenzymes are metalated by zinc and activated in the compartments of the early secretory pathway before reaching their destination. Zn transporter (ZNT) proteins located in these compartments are essential for ectoenzyme activation. We have previously reported that ZNT proteins, specifically ZNT5–ZNT6 heterodimers and ZNT7 homodimers, play critical roles in the activation of zinc ectoenzymes, such as alkaline phosphatases (ALPs), by mobilizing cytosolic zinc into these compartments. However, this process remains incompletely understood. Here, using genetically-engineered chicken DT40 cells, we first determined that Zrt/Irt-like protein (ZIP) transporters that are localized to the compartments of the early secretory pathway play only a minor role in the ALP activation process. These transporters included ZIP7, ZIP9, and ZIP13, performing pivotal functions in maintaining cellular homeostasis by effluxing zinc out of the compartments. Next, using purified ALP proteins, we showed that zinc metalation on ALP produced in DT40 cells lacking ZNT5–ZNT6 heterodimers and ZNT7 homodimers is impaired. Finally, by genetically disrupting both ZNT5 and ZNT7 in human HAP1 cells, we directly demonstrated that the tissue-nonspecific ALP-activating functions of both ZNT complexes are conserved in human cells. Furthermore, using mutant HAP1 cells, we uncovered a previously-unrecognized and unique spatial regulation of ZNT5–ZNT6 heterodimer formation, wherein ZNT5 recruits ZNT6 to the Golgi apparatus to form the heterodimeric complex. These findings fill in major gaps in our understanding of the molecular mechanisms underlying zinc ectoenzyme activation in the compartments of the early secretory pathway.

scholarly journals Evidence for Segregation of Sphingomyelin and Cholesterol during Formation of Copi-Coated Vesicles

2000 ◽  
Vol 151 (3) ◽  
pp. 507-518 ◽  
Author(s):  
Britta Brügger ◽  
Roger Sandhoff ◽  
Sabine Wegehingel ◽  
Karin Gorgas ◽  
Jörg Malsam ◽  
...  
Keyword(s):  
Cholesterol Synthesis ◽  
Secretory Pathway ◽  
Molecular Mechanisms ◽  
Lipid Analysis ◽  
Coated Vesicles ◽  
Early Secretory Pathway ◽  
Golgi Membranes ◽  
A Cell ◽  
Higher Eukaryotes ◽  
Specific Lipid

In higher eukaryotes, phospholipid and cholesterol synthesis occurs mainly in the endoplasmic reticulum, whereas sphingomyelin and higher glycosphingolipids are synthesized in the Golgi apparatus. Lipids like cholesterol and sphingomyelin are gradually enriched along the secretory pathway, with their highest concentration at the plasma membrane. How a cell succeeds in maintaining organelle-specific lipid compositions, despite a steady flow of incoming and outgoing transport carriers along the secretory pathway, is not yet clear. Transport and sorting along the secretory pathway of both proteins and most lipids are thought to be mediated by vesicular transport, with coat protein I (COPI) vesicles operating in the early secretory pathway. Although the protein constituents of these transport intermediates are characterized in great detail, much less is known about their lipid content. Using nano-electrospray ionization tandem mass spectrometry for quantitative lipid analysis of COPI-coated vesicles and their parental Golgi membranes, we find only low amounts of sphingomyelin and cholesterol in COPI-coated vesicles compared with their donor Golgi membranes, providing evidence for a significant segregation from COPI vesicles of these lipids. In addition, our data indicate a sorting of individual sphingomyelin molecular species. The possible molecular mechanisms underlying this segregation, as well as implications on COPI function, are discussed.

Membrane traffic related to endosome dynamics and protein secretion in filamentous fungi

2021 ◽  
Author(s):  
Yujiro Higuchi
Keyword(s):  
Filamentous Fungi ◽  
Protein Secretion ◽  
Secretory Pathway ◽  
Molecular Mechanisms ◽  
Membrane Traffic ◽  
Early Endosome ◽  
Protein Glycosylation ◽  
Hyphal Cell ◽  
Cell Factories ◽  
Membrane Contacts

ABSTRACT In eukaryotic cells, membrane-surrounded organelles are orchestrally organized spatiotemporally under environmental situations. Among such organelles, vesicular transports and membrane contacts occur to communicate each other, so-called membrane traffic. Filamentous fungal cells are highly polarized and thus membrane traffic is developed to have versatile functions. Early endosome (EE) is an endocytic organelle that dynamically exhibits constant long-range motility through the hyphal cell, which is proven to have physiological roles, such as other organelle distribution and signal transduction. Since filamentous fungal cells are also considered as cell factories, to produce valuable proteins extracellularly, molecular mechanisms of secretory pathway including protein glycosylation have been well investigated. In this review, molecular and physiological aspects of membrane traffic especially related to EE dynamics and protein secretion in filamentous fungi are summarized, and perspectives for application are also described.

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