autophagy xenophagy l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Autophagy/xenophagy PowerPoint Presentation
Download Presentation
Autophagy/xenophagy

Loading in 2 Seconds...

play fullscreen
1 / 35

Autophagy/xenophagy - PowerPoint PPT Presentation


  • 1946 Views
  • Uploaded on

Autophagy/xenophagy Autophagy “eat onself” Xenophagy “eat foreign matter” Highly conserved and regulated process that maintains cellular homeostasis and protects cells against starvation and microbe invasion 3 types: macro-autophagy Microautophagy chaperone-mediated autophagy

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Autophagy/xenophagy' - Thomas


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
autophagy xenophagy
Autophagy/xenophagy
  • Autophagy “eat onself”
  • Xenophagy “eat foreign matter”
  • Highly conserved and regulated process that maintains cellular homeostasis and protects cells against starvation and microbe invasion
  • 3 types:
    • macro-autophagy
    • Microautophagy
    • chaperone-mediated autophagy
manipulating host responses
Manipulating host responses
  • Autophagy
  • Apoptosis
autophagic process
Autophagic process
  • Cytoplasmic organelles and portions of cytoplasm sequestered in double membrane-bound vacuoles
  • Source of membrane multifactorial (ribosome-free ER?)
  • Fuse with lysosomes

Nature reviews microbiology 2004 2:301

Science 2004 306:990

3 stages
3 Stages
  • Initiation: nutrient starvation, growth factor-mediated starvation
  • Execution
  • Maturation

Nature reviews microbiology 2004 2:301

initiation signaling pathways
Initiation:Signaling pathways
  • Trimeric G proteins
  • Growth receptors
  • PI3K (classes I & III)
  • protein phosphatases
  • mTOR
execution
Execution
  • Requires covalent-conjugation pathways
  • Requires Atg3, Atg7, Atg10
    • Homologs of ubiquitinylation proteins
    • Modifies pathway components but does not target them for degradation
execution cont
Execution (cont)
  • Production of PIP3 via hVPS34 (class III PI3K)
    • Inhibited by wortmanin, 3-Methyladenine
    • Promotes proteolysis->production of amino acids
  • Complex formed between hVPS34, Atg14, & Atg6 (Beclin-1) which is necessary for downstream recruitment and localization of Atg5 & Atg12
  • Covalent linkage of Atg5 and Atg12 on pre-autophagosomal membrane
  • Protease cleavage of Atg8 (MAP1 Light chain 3 (LC3), followed by covalent lipidation to phosphatidylethanolamine and translocation to autophagosome membrane
fusion
Fusion
  • Autophagosomes fuse with endosomes
  • Acquire characteristics of lysosomes
    • LAMP1 & 2
    • Accessible to DAMP
    • Cathepsins, acid phosphatases
  • Vesicle fusion mediated by Rabs (Rab24)
assays for autophagy
Assays for autophagy
  • EM
  • Marker labeling
    • Atg5: early autophagosomes
    • Atg8/LCM3: early & late
    • Lysosomal markers (DAMP, lysosotracker)
    • Monodansylcadaverine-fluorescent marker staining
  • Genetically tractable organisms
  • Knockout cells (Atg-5)
  • Inhibitors (wortmannin, 3-MA)
  • Inducers (amino acid starvation, rapamycin, IFN-gamma)
involved in many processes
Involved in many processes
  • ATG6/Beclin 1: tumour suppressor gene
    • Deleted in sporadic breast, ovarian, prostate CA
  • Dauer formation in C. elegans
  • ATG5 & ATG7: Dictyostelium nitrogen starvation
  • Prevent premature senescence
  • Host defense against pathogen invasion
microbes autophagy
Microbes & autophagy
  • Diverse strategies
    • Host defense
    • Bacterial manipulate it to survive intracellularly

Nature reviews microbiology 2004 2:301

legionella
Legionella
  • “pregnant pause” hypothesis
    • Initially enter into autophagosomes
    • Require type IV effector to delay maturation into lysosomes
legionella14
Legionella
  • Membranous vacuole surrounded by double membrane
  • Contains ER protein (BiP)
  • Contains LAMP1, cathepsin D
  • Dot/ICM mutants: enter late endosomes/lysosomes
  • Controversial
    • ER membrane
    • Inhibited by DN SAR1 & ARF1, involved in ER-golgi trafficking
    • Normal intracellular development in dictyostelium Atg1, atg5, atg6, atg7, atg8 genes
streptococcus pyogenes aka group a strep gas
Streptococcus pyogenes aka Group A Strep (GAS)
  • Sore throat
    • Glomerulonephritis
    • Rheumatic fever and valvular heart disease
  • Toxin-mediated skin infections
    • Impetigo
    • Scarlet Fever
  • Necrotizing fasciitis (flesh eating bacteria)
  • Toxic shock-like syndrome
grpa strep autophagy as host defense
GrpA strepAutophagy as host defense
  • Binds to ECM & produces toxins
  • Invades non-phagocytic cells->vacuolar escape->degraded by autophagy
    • Initially enters early endosome (EEA1+)
    • Requires SLO to escape and enter autophagic pathway
    • Vacuolar escape mutant (∆SLO) avoids autophagy
  • Atg5 deficient cells
    • Vacuolar escape
    • Avoids autophagic destruction
    • Modest increase in intracellular bacterial titers
  • Host cell ultimately undergo apoptosis
slide18
M. Tb
  • Induction of autophagy (AA starvation, rapamycin) augments phagolysome acidification
    • Blocked by Wortmannin & 3-MA
  • Induction of autophagy promotes maturation of phagolysosome
    • Acquisition of cathepsin D, Lamp-1, vacuolar ATPase, LBPA
  • Induction of autophagy promotes co-localization of autophagic markers (LC3, beclin-1)
  • Induction of autophagy inhibits mycobacterial survival
  • Mimicked by IFN-gamma
shigella a bug that disarms autophagy ogawa et al science 2005

Atg5

IcsB

VirG

Shigellaa bug that disarms autophagyOgawa et al Science 2005

Atg5

No autophagy

VirG

Atg5

∆IcsB:autophagy

IcsB

∆VirG: no autophagy

apoptosis
Apoptosis
  • Programmed cell death
    • Type I: caspase mediated
    • Type II: autophagy-mediated
  • Entire cell dismantled within membrane-enclosed vesicles
  • Taken up by phagocytes, preventing release of intracellular components from dying cells
  • Normal morphogenesis, removing genetically damaged cells, proper tissue homeostasis, invading microbes
mechanism
Mechanism
  • Sequential activation of cysteine proteases (caspases)
    • Caspase 1-related: 1,4,5,13,14
      • Cytokine processing and pro-inflammatory cell death
    • Initiator caspases: 2, 8, 9, 10
    • Effector caspases: 3,6,7
  • Regulated process
    • Extrinsic: stimulation of Fas or TNFR surface receptors
    • Intrinsic: altered mitochondrial membrane integrity
necrosis
Necrosis
  • Cell swelling and rupture
  • Release in intracellular components
  • Activation of inflammatory response
  • Can be regulated
  • Can occur in concert with or instead of apoptosis (e.g. if apoptosis is blocked)
pyroptosis
Pyroptosis
  • Caspase-1-dependent cell death
  • Convert IL-1B and IL-18 to active forms
  • Induced by Shigella IpaB and Salmonella SipB
apoptosis friend or foe
Apoptosis: friend or foe
  • Host view
    • Apoptosis is bad unless it takes away a privileged intracellular niche
  • Pathogen view
    • Inhibit apoptosis to provide for intracellular niche (Chlamydia)
    • Promote apoptosis (Yersinia, Shigella)
      • Dismantle host defense
      • Promote microbe dissemination
    • Many bacterial molecules can modulate apoptosis
      • Toxins
      • Type III secreted proteins
chlamydia species
Chlamydia species
  • Obligate intracellular bacteria
  • Interesting intracellular life cycle
  • Chlamydia trachomatis
    • Major cause of STDs in US and trachoma in developing countries
  • Chlamydia pneumoniae
    • Important cause of upper and lower respiratory infections
    • Possible association with atherosclerotic heart disease
slide29
Diverges from endoctyic pathway immediately
  • Acquires characteristics of golgli
    • Sphingomyelin
    • Cholesterol
    • Rab1 (ER to golgi trafficking), Rab 11 (recycling endosomes, TGN, plasma membrane), Rab 6 (Golgi-ER trafficking, EE to TGN transport)
chlamydia modulates apoptosis
Chlamydia modulates apoptosis
  • Chlamydiae-infected cells are protected against mitochondria-dependent cell death but not caspase-3 mediated cell death
  • Inhibits cytochrome C release
  • Destroys pro-apoptotic BH3 domain containing proteins (Bim/Bod, Puma, Bad) which are upstream of Bax/Bak
chlamydia both induces and inhibits apoptosis
Chlamydia both induces and inhibits apoptosis
  • Chlamydia protein associated with death domains, that interacts with death domains of TNF receptors to activate apoptotic caspases
salmonella induced cell death is complicated
Salmonella-induced cell death is complicated
  • Mutiple mechanisms
    • Appears heterogeneous
    • Apoptosis, necrosis, pyrotosis
  • SPI-1-dependent caspase-1 dependent cell death
    • Rapid
    • Caspase-1 dependent
    • Caspase-3 independent
    • SipB-dependent
    • SipB forms complex with Caspase-1
slide33
SPI-1 dependent caspase-1 independent cell death
    • Slower
    • SipB-dependent
    • Expression of SipB in caspase-1 deficient cells lead to formation of lamellar structures..autophagosomes? Fusing to mitochondria
    • SipB has fusogenic properties
spi 2 dependent macrophage cell death
SPI-2-dependent macrophage cell death
  • Prolonged incubation (24 hrs)
  • Caspase-1-dependent
  • Caspase-1-deficient mice are resistant to Salmonella infection