1 / 19

Zipper Mechanism

Zipper Mechanism. Ingestion occurs by sequential engagement of the phagocyte membrane with the particle surface. Pseudopod advance proceeds no further than the receptor-ligand interaction permits. TRIGGER MECHANISM. Particle binding initiates an ‘all or none’ phagocytic response.

alpha
Download Presentation

Zipper Mechanism

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. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Zipper Mechanism • Ingestion occurs by sequential engagement of the phagocyte membrane with the particle surface. Pseudopod advance proceeds no further than the receptor-ligand interaction permits.

  2. TRIGGER MECHANISM • Particle binding initiates an ‘all or none’ phagocytic response.

  3. Salmonellosis Factors for disease: Pathogen – Virulence? Host – Immune function? Environment – Dose? http://www.worldwidevaccines.com/typhoid/typhoid_4.jpg

  4. Salmonella Virulence • SPI-1: TTSS to deliver effector proteins to cytoplasm that induce cytoskeletal rearrangments to facilitate Salmonella uptake in SCV. • SPI-2: TTSS to deliver effector proteins from SCV to cell cytoplasm that induce focal actin condensation around SCV. • spv: prevents actin polymerization needed for F-actin filament formation.

  5. SIGNALS FROM OUTSIDE • How to invade non-phagocytic cells? • SPI-1 TTSS: • Activate regulators Cdc42 and Rac1 in host. • Bacteria-host interaction to promote polymerization and bundling of actin filaments. • Restore normal actin dynamics after invasion.

  6. MEMBRANE RUFFLING Ruffles, Macropinocytosis, Engulfment: • Sop B, E, E2 activate GTPases Cdc42, Rac1. • Activate WASP, Scar/Wave, Arp2/3 to initiate actin polymerization. • Translocate: • SipC – Insert in target cell membrane, direct filament formation at sites adjacent to bacteria? • SipA – ‘Molecular staple’ to stabilize actin filaments. • SptP – Reverse cytoskeletal rearrangements.

  7. SIGNALS FROM INSIDE • How to proliferate within cells? • SPI-2 TTSS: • Translocate effectors from SCV to cytoplasm: • Form filamentous endosomes • Decrease recruitment of NADPH oxidase • Change SCV fusion pathway • VAP formation of actin around SCV • SpvB: • Depolymerizes actin from F filaments to G monomers with ADP ribosylation.

  8. TIMING IS EVERYTHING • Events are carefully orchestrated: • Focal actin polymerization for cell invasion. • Caused by SPI-1 effectors • Reversed by SptP • Focal actin condensation for effects from SCV. • Caused by SPI-2 effectors • Reversed by SpvB • Depolymerization leads to apoptosis and further Salmonella phagocytosis!

  9. Does all this talk of phagocytosis make you hungry? The End http://www.sph.tulane.edu/%7Edmsander/WWW/Video/Macmov.html

More Related