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De Mazière A, van der Beek J, van Dijk S, de Heus C, Reggiori F, Koike M, Klumperman J. An optimized protocol for immuno-electron microscopy of endogenous LC3. Autophagy 2022; 18:3004-3022. [PMID: 35387562 PMCID: PMC9673964 DOI: 10.1080/15548627.2022.2056864] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
MAP1LC3/LC3 (microtubule associated protein 1 light chain 3) is widely used as marker of autophagic compartments at different stages of maturation. Electron microscopy (EM) combined with immunolabeling is the only technique that can reveal the ultrastructural identity of LC3-labeled compartments. However, immuno-EM of endogenous LC3 proteins has proven difficult. Here, we test a panel of commercially available antibodies and apply different labeling conditions to present an optimized procedure for LC3 immuno-EM. Using ultrathin cryosections and protein A-colloidal gold or gold enhancement labeling, we localize endogenous LC3 in starved cells or tissues in the presence or absence of the proton pump inhibitor bafilomycin A1. We localize LC3 to early and late stage autophagic compartments that can be classified by their morphology. By on-section correlative light-electron microscopy (CLEM) we show that comparable fluorescent LC3-positive puncta can represent different autophagic intermediates. We also show that our approach is sufficiently robust to label endogenous LC3 simultaneously with other lysosomal and autophagy markers, LAMP1 or SQSTM1/p62, and can be used for quantitative approaches. Thus, we demonstrate that bafilomycin A1 treatment from 2.5 up to 24 h does not inhibit fusion between autophagosomes and lysosomes, but leads to the accumulation of LC3-positive material inside autolysosomes. Together, this is the first study presenting an extensive overview of endogenous LC3 localization at ultrastructural resolution without the need for cell permeabilization and using a commercially available antibody. This provides researchers with a tool to study canonical and non-canonical roles of LC3 in native conditions.Abbreviations: BafA1: bafilomycin A1; BSA: bovine serum albumin; BSA-c: acetylated BSA; BSA5: BSA conjugated to 5-nm gold particles; CLEM: correlative light-electron microscopy; EGFP: enhanced green fluorescent protein; EM: electron microscopy; FBS: fetal bovine serum; FSG: fish skin gelatin; GA: glutaraldehyde; IF: immunofluorescence; LAMP1: lysosomal associated membrane protein 1; LC3s: LC3 proteins; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; ON: overnight; PAG: protein A-conjugated gold particles; PAG1-3: PAG5, PAG10, PAG15, protein A conjugated to 1-3-, 5-, 10-, or 15-nm gold particles; PB: Sorensen's phosphate buffer; PBS: phosphate-buffered saline; PFA: paraformaldehyde; RT: room temperature.
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Affiliation(s)
- Ann De Mazière
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Jan van der Beek
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Suzanne van Dijk
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Cecilia de Heus
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Fulvio Reggiori
- Department of Biomedical Sciences of Cells & Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Masato Koike
- Department of Cell Biology and Neuroscience, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Judith Klumperman
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands,CONTACT Judith Klumperman Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
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2
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Dejanovic B, Wu T, Tsai MC, Graykowski D, Gandham VD, Rose CM, Bakalarski CE, Ngu H, Wang Y, Pandey S, Rezzonico MG, Friedman BA, Edmonds R, De Mazière A, Rakosi-Schmidt R, Singh T, Klumperman J, Foreman O, Chang MC, Xie L, Sheng M, Hanson JE. Complement C1q-dependent excitatory and inhibitory synapse elimination by astrocytes and microglia in Alzheimer's disease mouse models. Nat Aging 2022; 2:837-850. [PMID: 37118504 PMCID: PMC10154216 DOI: 10.1038/s43587-022-00281-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 08/05/2022] [Indexed: 04/30/2023]
Abstract
Microglia and complement can mediate neurodegeneration in Alzheimer's disease (AD). By integrative multi-omics analysis, here we show that astrocytic and microglial proteins are increased in TauP301S synapse fractions with age and in a C1q-dependent manner. In addition to microglia, we identified that astrocytes contribute substantially to synapse elimination in TauP301S hippocampi. Notably, we found relatively more excitatory synapse marker proteins in astrocytic lysosomes, whereas microglial lysosomes contained more inhibitory synapse material. C1q deletion reduced astrocyte-synapse association and decreased astrocytic and microglial synapses engulfment in TauP301S mice and rescued synapse density. Finally, in an AD mouse model that combines β-amyloid and Tau pathologies, deletion of the AD risk gene Trem2 impaired microglial phagocytosis of synapses, whereas astrocytes engulfed more inhibitory synapses around plaques. Together, our data reveal that astrocytes contact and eliminate synapses in a C1q-dependent manner and thereby contribute to pathological synapse loss and that astrocytic phagocytosis can compensate for microglial dysfunction.
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Affiliation(s)
- Borislav Dejanovic
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA.
- Department of Neuroscience, Genentech, South San Francisco, CA, USA.
| | - Tiffany Wu
- Department of Neuroscience, Genentech, South San Francisco, CA, USA
| | - Ming-Chi Tsai
- Department of Neuroscience, Genentech, South San Francisco, CA, USA
| | - David Graykowski
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Vineela D Gandham
- Department of Biomedical Imaging, Genentech, South San Francisco, CA, USA
| | - Christopher M Rose
- Department of Microchemistry Proteomics and Lipidomics, Genentech, South San Francisco, CA, USA
| | - Corey E Bakalarski
- Department of Microchemistry Proteomics and Lipidomics, Genentech, South San Francisco, CA, USA
| | - Hai Ngu
- Department of Pathology, Genentech, South San Francisco, CA, USA
| | - Yuanyuan Wang
- Department of Neuroscience, Genentech, South San Francisco, CA, USA
| | - Shristi Pandey
- Department of OMNI Bioinformatics, Genentech, South San Francisco, CA, USA
| | | | - Brad A Friedman
- Department of OMNI Bioinformatics, Genentech, South San Francisco, CA, USA
| | - Rose Edmonds
- Department of Biomarker Development, Genentech, South San Francisco, CA, USA
| | - Ann De Mazière
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Raphael Rakosi-Schmidt
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Tarjinder Singh
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Judith Klumperman
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Oded Foreman
- Department of Pathology, Genentech, South San Francisco, CA, USA
| | - Michael C Chang
- Department of Biomarker Development, Genentech, South San Francisco, CA, USA
| | - Luke Xie
- Department of Biomedical Imaging, Genentech, South San Francisco, CA, USA
| | - Morgan Sheng
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Neuroscience, Genentech, South San Francisco, CA, USA
| | - Jesse E Hanson
- Department of Neuroscience, Genentech, South San Francisco, CA, USA.
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Gao X, Mazière AD, Beard R, Klumperman J, Hannoush RN. Fatty acylation enhances the cellular internalization and cytosolic distribution of a cystine-knot peptide. iScience 2021; 24:103220. [PMID: 34712919 PMCID: PMC8529511 DOI: 10.1016/j.isci.2021.103220] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 06/14/2021] [Accepted: 09/30/2021] [Indexed: 02/07/2023] Open
Abstract
Delivering peptides into cells could open up possibilities for targeting intracellular proteins. Although fatty acylation of peptide therapeutics improves their systemic half-life, it remains unclear how it influences their cellular uptake. Here, we demonstrate that a fatty acylated peptide exhibits enhanced cellular internalization and cytosolic distribution compared to the un-acylated version. By using a cystine-knot peptide as a model system, we report an efficient strategy for site-specific conjugation of fatty acids. Peptides modified with fatty acids of different chain lengths entered cells through clathrin-mediated and macropinocytosis pathways. The cellular uptake was mediated by the length of the hydrocarbon chain, with myristic acid conjugates displaying the highest distribution across the cytoplasm including the cytosol, and endomembranes of the ER, Golgi and mitochondria. Our studies demonstrate how fatty acylation improves the cellular uptake of peptides, and lay the groundwork for future development of bioactive peptides with enhanced intracellular distribution. A synthetic strategy comprises site-specific conjugation of fatty acids to peptides Fatty acylation of a peptide enhances its cellular uptake and cytosolic distribution Myristoylated peptides display a high cytoplasmic distribution Fatty acylated peptides are internalized via multiple endocytic routes
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Affiliation(s)
- Xinxin Gao
- Department of Early Discovery Biochemistry, Genentech, South San Francisco, CA, USA
| | - Ann De Mazière
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Rhiannon Beard
- Department of Early Discovery Biochemistry, Genentech, South San Francisco, CA, USA
| | - Judith Klumperman
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Rami N Hannoush
- Department of Early Discovery Biochemistry, Genentech, South San Francisco, CA, USA
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Tran NH, Carter SD, De Mazière A, Ashkenazi A, Klumperman J, Walter P, Jensen GJ. The stress-sensing domain of activated IRE1α forms helical filaments in narrow ER membrane tubes. Science 2021; 374:52-57. [PMID: 34591618 PMCID: PMC9041316 DOI: 10.1126/science.abh2474] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The signaling network of the unfolded protein response (UPR) adjusts the protein-folding capacity of the endoplasmic reticulum (ER) according to need. The most conserved UPR sensor, IRE1α, spans the ER membrane and activates through oligomerization. IRE1α oligomers accumulate in dynamic foci. We determined the in situ structure of IRE1α foci by cryogenic correlated light and electron microscopy combined with electron cryo-tomography and complementary immuno–electron microscopy in mammalian cell lines. IRE1α foci localized to a network of narrow anastomosing ER tubes (diameter, ~28 nm) with complex branching. The lumen of the tubes contained protein filaments, which were likely composed of arrays of IRE1α lumenal domain dimers that were arranged in two intertwined, left-handed helices. This specialized ER subdomain may play a role in modulating IRE1α signaling.
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Affiliation(s)
- Ngoc-Han Tran
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Stephen D. Carter
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Ann De Mazière
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, Netherlands
| | - Avi Ashkenazi
- Cancer Immunology, Genentech, Inc., South San Francisco, CA, USA
| | - Judith Klumperman
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, Netherlands
| | - Peter Walter
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
- Corresponding author. (P.W.); (G.J.J.)
| | - Grant J. Jensen
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
- Corresponding author. (P.W.); (G.J.J.)
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Gao X, De Mazière A, Iaea DB, Arthur CP, Klumperman J, Ciferri C, Hannoush RN. Visualizing the cellular route of entry of a cystine-knot peptide with Xfect transfection reagent by electron microscopy. Sci Rep 2019; 9:6907. [PMID: 31061420 PMCID: PMC6502800 DOI: 10.1038/s41598-019-43285-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 04/16/2019] [Indexed: 01/08/2023] Open
Abstract
Cystine-knot peptides are attractive templates in drug discovery due to a number of features they possess including their 3D conformation, physicochemical stability and synthetic tractability. Yet, their cellular uptake mechanisms remain largely unexplored. Recently, we demonstrated that the cystine-knot peptide EETI-II is internalized into cells and that its cellular uptake could be modulated by using a protein transfection reagent Xfect. However, the mechanism of Xfect-mediated cellular internalization of EETI-II remained unclear. Here, by using high resolution electron microscopy, we observe the formation of EETI-II-positive macropinosomes and clathrin-coated pits at early time points after treatment of cells with EETI-II/Xfect complexes. Internalized EETI-II subsequently accumulates in intracellular Xfect-induced detergent-resistant membrane compartments which appear to lack characteristic endosomal or lysosomal markers. Notably, Xfect enables the uptake of cell impermeable nuclear dyes into similar intracellular compartments that do not seem to deliver the cargo to the cytosol or nucleus. Altogether, our findings reveal mechanistic insights into the cellular uptake route of Xfect, and underscore the need for the development of effective tools to enhance the cytosolic delivery of cystine-knot peptides. Finally, our data illustrate that electron microscopy is a powerful approach for studying endocytic mechanisms of cell-penetrating peptides and their effects on cellular membranes.
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Affiliation(s)
- Xinxin Gao
- Department of Early Discovery Biochemistry, Genentech, South San Francisco, California, USA
| | - Ann De Mazière
- Section of Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - David B Iaea
- Department of Biochemical and Cellular Pharmacology, Genentech, South San Francisco, California, USA
| | - Christopher P Arthur
- Department of Structural Biology, Genentech, South San Francisco, California, USA
| | - Judith Klumperman
- Section of Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Claudio Ciferri
- Department of Structural Biology, Genentech, South San Francisco, California, USA
| | - Rami N Hannoush
- Department of Early Discovery Biochemistry, Genentech, South San Francisco, California, USA.
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Johnson L, Huseni M, Smyczek T, Lima A, Yeung S, Cheng JH, Molina R, Kan D, De Mazière A, Klumperman J, Kasman I, Zhang Y, Dennis MS, Eastham-Anderson J, Jubb AM, Hwang O, Desai R, Schmidt M, Nannini MA, Barck KH, Carano RAD, Forrest WF, Song Q, Chen DS, Naumovski L, Singh M, Ye W, Hegde PS. Anti-EGFL7 antibodies enhance stress-induced endothelial cell death and anti-VEGF efficacy. J Clin Invest 2013; 123:3997-4009. [PMID: 23945239 DOI: 10.1172/jci67892] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Accepted: 06/13/2013] [Indexed: 01/13/2023] Open
Abstract
Many oncology drugs are administered at their maximally tolerated dose without the knowledge of their optimal efficacious dose range. In this study, we describe a multifaceted approach that integrated preclinical and clinical data to identify the optimal dose for an antiangiogenesis agent, anti-EGFL7. EGFL7 is an extracellular matrix-associated protein expressed in activated endothelium. Recombinant EGFL7 protein supported EC adhesion and protected ECs from stress-induced apoptosis. Anti-EGFL7 antibodies inhibited both of these key processes and augmented anti-VEGF-mediated vascular damage in various murine tumor models. In a genetically engineered mouse model of advanced non-small cell lung cancer, we found that anti-EGFL7 enhanced both the progression-free and overall survival benefits derived from anti-VEGF therapy in a dose-dependent manner. In addition, we identified a circulating progenitor cell type that was regulated by EGFL7 and evaluated the response of these cells to anti-EGFL7 treatment in both tumor-bearing mice and cancer patients from a phase I clinical trial. Importantly, these preclinical efficacy and clinical biomarker results enabled rational selection of the anti-EGFL7 dose currently being tested in phase II clinical trials.
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Affiliation(s)
- Leisa Johnson
- Genentech Inc., South San Francisco, California 94080, USA.
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Abstract
Akt has emerged as an attractive cancer therapeutic target with a central role in cell survival, growth, proliferation and metabolism.A key to the clinical success of Akt inhibitors is the maximal possible antitumor efficacy achievable without intolerable side effects. In our recent work, we show that although Akt inhibition does not always induce a clear apoptotic response, autophagy is a more readily detectable response to pan-Akt knockdown or selective small molecule inhibitors of the PI3K/Akt pathway. Autophagy isa catabolic process of bulk lysosomal degradation and recycling of cytoplasmic material and organelles, which can provide a temporary survival mechanism for cells under stress conditions, but can also make cells vulnerable to several forms of cell death under specific circumstances. We hypothesize that autophagy induced by Akt inhibition may sensitize tumor cells to agents targeting the later steps of this lysosomal degradation process. Indeed, agents that interfere with the lysosomal degradation function could precipitate cell death when combined with Akt inhibition and promote complete tumor remissions in preclinical models. These findings suggest that manipulating the autophagic response may be a promising strategy to increase the therapeutic efficacy of Akt inhibitors.
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Affiliation(s)
- Michael Degtyarev
- Department of Cancer Signaling and Translational Oncology, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
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Collins CA, De Mazière A, van Dijk S, Carlsson F, Klumperman J, Brown EJ. Atg5-independent sequestration of ubiquitinated mycobacteria. PLoS Pathog 2009; 5:e1000430. [PMID: 19436699 PMCID: PMC2673685 DOI: 10.1371/journal.ppat.1000430] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Accepted: 04/14/2009] [Indexed: 12/19/2022] Open
Abstract
Like several other intracellular pathogens, Mycobacterium marinum (Mm) escapes from phagosomes into the host cytosol where it can polymerize actin, leading to motility that promotes spread to neighboring cells. However, only approximately 25% of internalized Mm form actin tails, and the fate of the remaining bacteria has been unknown. Here we show that cytosolic access results in a new and intricate host pathogen interaction: host macrophages ubiquitinate Mm, while Mm shed their ubiquitinated cell walls. Phagosomal escape and ubiquitination of Mm occurred rapidly, prior to 3.5 hours post infection; at the same time, ubiquitinated Mm cell wall material mixed with host-derived dense membrane networks appeared in close proximity to cytosolic bacteria, suggesting cell wall shedding and association with remnants of the lysed phagosome. At 24 hours post-infection, Mm that polymerized actin were not ubiquitinated, whereas ubiquitinated Mm were found within LAMP-1-positive vacuoles resembling lysosomes. Though double membranes were observed which sequestered Mm away from the cytosol, targeting of Mm to the LAMP-1-positive vacuoles was independent of classical autophagy, as demonstrated by absence of LC3 association and by Atg5-independence of their formation. Further, ubiquitination and LAMP-1 association did not occur with mutant avirulent Mm lacking ESX-1 (type VII) secretion, which fail to escape the primary phagosome; apart from its function in phagosome escape, ESX-1 was not directly required for Mm ubiquitination in macrophages or in vitro. These data suggest that virulent Mm follow two distinct paths in the cytosol of infected host cells: bacterial ubiquitination is followed by sequestration into lysosome-like organelles via an autophagy-independent pathway, while cell wall shedding may allow escape from this fate to permit continued residence in the cytosol and formation of actin tails.
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Affiliation(s)
- Cathleen A. Collins
- Department of Microbial Pathogenesis, Genentech, Inc., South San Francisco, California, United States of America
- Biomedical Sciences Graduate Program and Medical Scientist Training Program, University of California San Francisco, San Francisco, California, United States of America
| | - Ann De Mazière
- Cell Microscopy Center, Department of Cell Biology and Institute for Biomembranes, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Suzanne van Dijk
- Cell Microscopy Center, Department of Cell Biology and Institute for Biomembranes, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Fredric Carlsson
- Department of Microbial Pathogenesis, Genentech, Inc., South San Francisco, California, United States of America
| | - Judith Klumperman
- Cell Microscopy Center, Department of Cell Biology and Institute for Biomembranes, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Eric J. Brown
- Department of Microbial Pathogenesis, Genentech, Inc., South San Francisco, California, United States of America
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Degtyarev M, De Mazière A, Orr C, Lin J, Lee BB, Tien JY, Prior WW, van Dijk S, Wu H, Gray DC, Davis DP, Stern HM, Murray LJ, Hoeflich KP, Klumperman J, Friedman LS, Lin K. Akt inhibition promotes autophagy and sensitizes PTEN-null tumors to lysosomotropic agents. J Cell Biol 2008; 183:101-16. [PMID: 18838554 PMCID: PMC2557046 DOI: 10.1083/jcb.200801099] [Citation(s) in RCA: 345] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2008] [Accepted: 09/05/2008] [Indexed: 12/13/2022] Open
Abstract
Although Akt is known as a survival kinase, inhibitors of the phosphatidylinositol 3-kinase (PI3K)-Akt pathway do not always induce substantial apoptosis. We show that silencing Akt1 alone, or any combination of Akt isoforms, can suppress the growth of tumors established from phosphatase and tensin homologue-null human cancer cells. Although these findings indicate that Akt is essential for tumor maintenance, most tumors eventually rebound. Akt knockdown or inactivation with small molecule inhibitors did not induce significant apoptosis but rather markedly increased autophagy. Further treatment with the lysosomotropic agent chloroquine caused accumulation of abnormal autophagolysosomes and reactive oxygen species, leading to accelerated cell death in vitro and complete tumor remission in vivo. Cell death was also promoted when Akt inhibition was combined with the vacuolar H(+)-adenosine triphosphatase inhibitor bafilomycin A1 or with cathepsin inhibition. These results suggest that blocking lysosomal degradation can be detrimental to cancer cell survival when autophagy is activated, providing rationale for a new therapeutic approach to enhancing the anticancer efficacy of PI3K-Akt pathway inhibition.
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De Mazière A, Parker L, Van Dijk S, Ye W, Klumperman J. Egfl7 knockdown causes defects in the extension and junctional arrangements of endothelial cells during zebrafish vasculogenesis. Dev Dyn 2008; 237:580-91. [PMID: 18224713 DOI: 10.1002/dvdy.21441] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The endothelial cell (EC) -specific secreted protein EGFL7 is important for tubulogenesis in newly forming blood vessels. We studied its role in vascular tube formation by a quantitative ultrastructural analysis of Egfl7-knockdown zebrafish embryos. At 24 hours postfertilization, the endothelia of dorsal aorta (DA) and posterior cardinal vein (PCV) were correctly anchored to the hypochord and endoderm, respectively, but failed to expand into the vascular area. This resulted in vessels with reduced or split lumen and open sheets of ECs. Concomitantly, the organization of hematopoietic cells-identified by the presence of previously undescribed membrane tubules-between DA and PCV, and within the vessels, was severely disturbed. Strikingly, ectopic cell junctions occurred across the obstructed vessel lumen, on the luminal EC surfaces, which in control conditions never display junctions of any kind. These data suggest that Egfl7 provides ECs with a cue for their extension into the vascular area and in establishing EC cell polarity.
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Affiliation(s)
- Ann De Mazière
- Cell Microscopy Center, Department of Cell Biology, University Medical Center Utrecht and Institute for Biomembranes, Utrecht, Netherlands
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Griffith J, Mari M, De Mazière A, Reggiori F. A cryosectioning procedure for the ultrastructural analysis and the immunogold labelling of yeast Saccharomyces cerevisiae. Traffic 2008; 9:1060-72. [PMID: 18429928 DOI: 10.1111/j.1600-0854.2008.00753.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Yeast Saccharomyces cerevisiae has been a crucial model system for the study of a multitude of cellular processes because of its amenability to genetics, molecular biology and biochemical procedures. By contrast, the morphological analysis of this organism by immunoelectron microscopy (IEM) has remained in a primordial phase preventing researchers to routinely incorporate this technique into their investigations. Here, in addition to simple but detailed protocols to perform conventional electron microscopy (EM) on plastic embedded sections, we present a new IEM procedure adapted from the Tokuyasu method to prepare cryosections from mildly fixed cells. This novel approach allows an excellent cell preservation and the negatively stained membranes create superb contrast that leads to a unique resolution of the yeast morphology. This, plus the optimal preservation of the epitopes, permits combined localization studies with a fine resolution of protein complexes, vesicular carriers and organelles at an ultrastructural level. Importantly, we also show that this cryo-immunogold protocol can be combined with high-pressure freezing and therefore cryofixation can be employed if difficulties are encountered to immobilize a particular structure with chemical fixation. This new IEM technique will be a valuable tool for the large community of scientists using yeast as a model system, in particular for those studying membrane transport and dynamics.
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Affiliation(s)
- Janice Griffith
- Department of Cell Biology, University Medical Centre Utrecht, 3584 CX Utrecht, the Netherlands
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12
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Schmidt M, Paes K, De Mazière A, Smyczek T, Yang S, Gray A, French D, Kasman I, Klumperman J, Rice DS, Ye W. EGFL7 regulates the collective migration of endothelial cells by restricting their spatial distribution. Development 2007; 134:2913-23. [PMID: 17626061 DOI: 10.1242/dev.002576] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
During sprouting angiogenesis, groups of endothelial cells (ECs) migrate together in units called sprouts. In this study, we demonstrate that the vascular-specific secreted factor EGFL7 regulates the proper spatial organization of ECs within each sprout and influences their collective movement. In the homozygous Egfl7-knockout mice, vascular development is delayed in many organs despite normal EC proliferation, and 50% of the knockout embryos die in utero. ECs in the mutant vasculatures form abnormal aggregates and the vascular basement membrane marker collagen IV is mislocalized, suggesting that ECs fail to recognize the proper spatial position of their neighbors. Although the migratory ability of individual ECs in isolation is not affected by the loss of EGFL7, the aberrant spatial organization of ECs in the mutant tissues decreases their collective movement. Using in vitro and in vivo analyses, we showed that EGFL7 is a component of the interstitial extracellular matrix deposited on the basal sides of sprouts, a location suitable for conveying positional information to neighboring ECs. Taken together, we propose that EGFL7 defines the optimal path of EC movement by assuring the correct positioning of each EC in a nascent sprout.
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Affiliation(s)
- Maike Schmidt
- Tumor Biology and Angiogenesis Department, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
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