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  • American Association for the Advancement of Science (AAAS)  (7)
  • 1
    Online Resource
    Online Resource
    Finding Partners for PI3Kγ: When 84 Is Better Than 101
    American Association for the Advancement of Science (AAAS) ; 2009
    In:  Science Signaling Vol. 2, No. 74 ( 2009-06-09)
    Details
    In: Science Signaling, American Association for the Advancement of Science (AAAS), Vol. 2, No. 74 ( 2009-06-09)
    Abstract: Phosphatidylinositol 3-kinase (PI3K) enzymes phosphorylate phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P 2 , also known as PIP 2 ], a minor but critically important phospholipid of the inner leaflet of the plasma membrane. The resulting PtdIns(3,4,5)P 3 (PIP 3 ) acts as a membrane-bound attractant that recruits and activates a set of proteins to execute specific downstream signaling events to achieve the desired biological outcomes. Several genes that encode different PI3Ks exist in mammalian cells, and in the case of each PI3K, a partner protein that is tightly associated with the kinase ensures that the enzyme is localized to and activated at the correct membrane compartment. Excess PtdIns(3,4,5)P 3 is a major contributor to many forms of cancer, and dysregulation of PI3Ks leads to severe immunological and metabolic abnormalities. Given the multitude of proteins that are regulated by PtdIns(3,4,5)P 3 , it is puzzling that not all of these targets are activated as soon as the lipid is produced in the plasma membrane. Reports have begun to shed light on the mechanism by which cells can discriminate between PtdIns(3,4,5)P 3 depending on the distinct PI3K protein that produced it. A study shows that PtdIns(3,4,5)P 3 regulates the degranulation of mast cells, but only if it is made by a PI3K that is associated with a specific adaptor protein. This remarkable specificity challenges our views of how phosphoinositides regulate their downstream effectors.
    Type of Medium: Online Resource
    ISSN: 1945-0877 , 1937-9145
    URL: Article
    DOI: 10.1126/scisignal.274pe35
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2009
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  • 2
    Online Resource
    Online Resource
    Ribosome-associated vesicles: A dynamic subcompartment of the endoplasmic reticulum in secretory cells
    American Association for the Advancement of Science (AAAS) ; 2020
    In:  Science Advances Vol. 6, No. 14 ( 2020-04-03)
    Details
    In: Science Advances, American Association for the Advancement of Science (AAAS), Vol. 6, No. 14 ( 2020-04-03)
    Abstract: The endoplasmic reticulum (ER) is a highly dynamic network of membranes. Here, we combine live-cell microscopy with in situ cryo–electron tomography to directly visualize ER dynamics in several secretory cell types including pancreatic β-cells and neurons under near-native conditions. Using these imaging approaches, we identify a novel, mobile form of ER, ribosome-associated vesicles (RAVs), found primarily in the cell periphery, which is conserved across different cell types and species. We show that RAVs exist as distinct, highly dynamic structures separate from the intact ER reticular architecture that interact with mitochondria via direct intermembrane contacts. These findings describe a new ER subcompartment within cells.
    Type of Medium: Online Resource
    ISSN: 2375-2548
    URL: Article
    DOI: 10.1126/sciadv.aay9572
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2020
    detail.hit.zdb_id: 2810933-8
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  • 3
    Online Resource
    Online Resource
    PI4P and PI(4,5)P 2 Are Essential But Independent Lipid Determinants of Membrane Identity
    American Association for the Advancement of Science (AAAS) ; 2012
    In:  Science Vol. 337, No. 6095 ( 2012-08-10), p. 727-730
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 337, No. 6095 ( 2012-08-10), p. 727-730
    Abstract: The quantitatively minor phospholipid phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P 2 ] fulfills many cellular functions in the plasma membrane (PM), whereas its synthetic precursor, phosphatidylinositol 4-phosphate (PI4P), has no assigned PM roles apart from PI(4,5)P 2 synthesis. We used a combination of pharmacological and chemical genetic approaches to probe the function of PM PI4P, most of which was not required for the synthesis or functions of PI(4,5)P 2 . However, depletion of both lipids was required to prevent PM targeting of proteins that interact with acidic lipids or activation of the transient receptor potential vanilloid 1 cation channel. Therefore, PI4P contributes to the pool of polyanionic lipids that define plasma membrane identity and to some functions previously attributed specifically to PI(4,5)P 2 , which may be fulfilled by a more general polyanionic lipid requirement.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1222483
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2012
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
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  • 4
    Online Resource
    Online Resource
    Polarization of Chemoattractant Receptor Signaling During Neutrophil Chemotaxis
    American Association for the Advancement of Science (AAAS) ; 2000
    In:  Science Vol. 287, No. 5455 ( 2000-02-11), p. 1037-1040
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 287, No. 5455 ( 2000-02-11), p. 1037-1040
    Abstract: Morphologic polarity is necessary for chemotaxis of mammalian cells. As a probe of intracellular signals responsible for this asymmetry, the pleckstrin homology domain of the AKT protein kinase (or protein kinase B), tagged with the green fluorescent protein (PHAKT-GFP), was expressed in neutrophils. Upon exposure of cells to chemoattractant, PHAKT-GFP is recruited selectively to membrane at the cell's leading edge, indicating an internal signaling gradient that is much steeper than that of the chemoattractant. Translocation of PHAKT-GFP is inhibited by toxin-B from Clostridium difficile , indicating that it requires activity of one or more Rho guanosine triphosphatases.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.287.5455.1037
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2000
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
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  • 5
    Online Resource
    Online Resource
    Visualizing Cellular Phosphoinositide Pools with GFP-Fused Protein-Modules
    American Association for the Advancement of Science (AAAS) ; 2002
    In:  Science's STKE Vol. 2002, No. 125 ( 2002-03-26)
    Details
    In: Science's STKE, American Association for the Advancement of Science (AAAS), Vol. 2002, No. 125 ( 2002-03-26)
    Abstract: Inositol phospholipids are well known for their pivotal role in calcium signaling as precursors of important second messengers generated in response to various stimuli. However, over the last 10 years, inositides have also emerged as universal signaling components present in virtually every membrane of eukaryotic cells. These lipids are locally produced and degraded by the numerous inositide kinase and phosphatase enzymes, to control the recruitment and activity of protein signaling complexes in specific membrane compartments. The spatial and temporal constraints imposed on changes in cellular inositides pose new challenges in finding experimental techniques through which such changes can be examined. Taking advantage of the protein domains selected by evolution to recognize cellular phosphoinositides, we have created fluorescent molecules by fusing these domains to the improved version of green fluorescent protein (EGFP); the distribution of these fusion proteins can be followed within live cells, thereby reporting on changes in phosphoinositides. Although this technique is one of the few that provide information on phosphoinositide dynamics in live cells with subcellular resolution and has rapidly gained popularity, it also has limitations that need to be taken into account when interpreting the data. Here, we summarize our experience in designing and using these constructs and review our position concerning the interpretation of the data obtained by this technique.
    Type of Medium: Online Resource
    ISSN: 1525-8882
    URL: Article
    DOI: 10.1126/stke.2002.125.pl3
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2002
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  • 6
    Online Resource
    Online Resource
    Activation of STIM1-Orai1 Involves an Intramolecular Switching Mechanism
    American Association for the Advancement of Science (AAAS) ; 2010
    In:  Science Signaling Vol. 3, No. 148 ( 2010-11-16)
    Details
    In: Science Signaling, American Association for the Advancement of Science (AAAS), Vol. 3, No. 148 ( 2010-11-16)
    Abstract: Stromal interaction molecule 1 (STIM1) stimulates calcium ion (Ca 2+ ) entry through plasma membrane Orai1 channels in response to decreased Ca 2+ concentrations in the endoplasmic reticulum lumen. We identified an acidic motif within the STIM1 coiled-coil region that keeps its Ca 2+ activation domain [Ca 2+ release–activated Ca 2+ (CRAC) activation domain/STIM1-Orai activating region (CAD/SOAR)]—a cytoplasmic region required for its activation of Orai1—inactive. The sequence of the STIM1 acidic motif shows substantial similarity to that of the carboxyl-terminal coiled-coil segment of Orai1, which is the postulated site of interaction with STIM1. Mutations within this acidic region rendered STIM1 constitutively active, whereas mutations within a short basic segment of CAD/SOAR prevented Orai1 activation. We propose that the CAD/SOAR domain is released from an intramolecular clamp during STIM1 activation, allowing the basic segment to activate Orai1 channels. This evolutionarily conserved mechanism of STIM1 activation resembles the regulation of protein kinases by intramolecular silencing through pseudosubstrate binding.
    Type of Medium: Online Resource
    ISSN: 1945-0877 , 1937-9145
    URL: Article
    DOI: 10.1126/scisignal.2001122
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2010
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  • 7
    Online Resource
    Online Resource
    PI(3,4)P2-mediated cytokinetic abscission prevents early senescence and cataract formation
    American Association for the Advancement of Science (AAAS) ; 2021
    In:  Science Vol. 374, No. 6573 ( 2021-12-10)
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 374, No. 6573 ( 2021-12-10)
    Abstract: Cytokinetic membrane abscission is a spatially and temporally regulated process that requires ESCRT (endosomal sorting complexes required for transport)–dependent control of membrane remodeling at the midbody, a subcellular organelle that defines the cleavage site. Alteration of ESCRT function can lead to cataract, but the underlying mechanism and its relation to cytokinesis are unclear. We found a lens-specific cytokinetic process that required PI3K-C2α (phosphatidylinositol-4-phosphate 3-kinase catalytic subunit type 2α), its lipid product PI(3,4)P 2 (phosphatidylinositol 3,4-bisphosphate), and the PI(3,4)P 2 –binding ESCRT-II subunit VPS36 (vacuolar protein-sorting-associated protein 36). Loss of each of these components led to impaired cytokinesis, triggering premature senescence in the lens of fish, mice, and humans. Thus, an evolutionarily conserved pathway underlies the cell type–specific control of cytokinesis that helps to prevent early onset cataract by protecting from senescence.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.abk0410
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2021
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    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
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