Single molecule polymerization, annealing and bundling dynamics of SipA induced actin filaments.
Salmonella bacteria cause more than three million deaths each year. They hijack cells and inject among other proteins SipA via a "molecular syringe" into the cell, which can tether actin subunits in opposing strands to form mechanically stabilized filaments which rapidly reshape the cells surface into extended ruffles, leading to bacterial internalization. Exactly how these ruffles form at a single filament level remains unknown. Our real time total internal fluorescence microscopy observations show that both bidirectional elongation of actin by SipA as well as end-to-end annealing of SipA-actin filaments are rapid processes. Complementary electron microscopy investigations demonstrate that crowding agents in vitro readily induce stiff bundles of SipA-actin filaments. Taken together these three effects, rapid SipA induced actin polymerization, filament annealing and bundle formation due to molecular crowding can explain how Salmonella invades cells at molecular level.
Popp
David
D
ERATO Actin Filament Dynamics Project, Japan Science and Technology Corporation, c/o RIKEN Harima Institute at Spring 8, Kouto, Sayo, Hyogo 679-5148, Japan. dpopp@spring8.or.jp
Yamamoto
Akihiro
A
Iwasa
Mitsusada
M
Nitanai
Yasushi
Y
Maéda
Yuichiro
Y
D008841:Actin Cytoskeleton / Q000378:metabolism* / Q000648:ultrastructure; D000199:Actins / Q000378:metabolism*; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D051347:CapZ Actin Capping Protein / Q000378:metabolism; D002645:Chickens; D007700:Kinetics; D008840:Microfilament Proteins / Q000378:metabolism*; D008854:Microscopy, Electron; D011108:Polymers / Q000378:metabolism; D012475:Salmonella; D012480:Salmonella Infections / Q000378:metabolism* / Q000382:microbiology; D037521:Virulence Factors / Q000378:metabolism
D000199:Actins; D001426:Bacterial Proteins; D051347:CapZ Actin Capping Protein; D008840:Microfilament Proteins; D011108:Polymers; C118287:SipA protein, Salmonella; D037521:Virulence Factors