The RickA protein of Rickettsia conorii activates the Arp2/3 complex.
Actin polymerization, the main driving force for cell locomotion, is also used by the bacteria Listeria and Shigella and vaccinia virus for intracellular and intercellular movements. Seminal studies have shown the key function of the Arp2/3 complex in nucleating actin and generating a branched array of actin filaments during membrane extension and pathogen movement. Arp2/3 requires activation by proteins such as the WASP-family proteins or ActA of Listeria. We previously reported that actin tails of Rickettsia conorii, another intracellular bacterium, unlike those of Listeria, Shigella or vaccinia, are made of long unbranched actin filaments apparently devoid of Arp2/3 (ref. 4). Here we identify a R. conorii surface protein, RickA, that activates Arp2/3 in vitro, although less efficiently than ActA. In infected cells, Arp2/3 is detected on the rickettsial surface but not in actin tails. When expressed in mammalian cells and targeted to the membrane, RickA induces filopodia. Thus RickA-induced actin polymerization, by generating long actin filaments reminiscent of those present in filopodia, has potential as a tool for studying filopodia formation.
Gouin
Edith
E
Unité des Interactions Bactéries-Cellules, Institut Pasteur, 28 Rue du Docteur Roux, Paris 75015, France.
Egile
Coumaran
C
Dehoux
Pierre
P
Villiers
Véronique
V
Adams
Josephine
J
Gertler
Frank
F
Li
Rong
R
Cossart
Pascale
P
D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D020114:Rickettsia conorii / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D000199:Actins; D001426:Bacterial Proteins; D003598:Cytoskeletal Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins