Clustering of Nck by a 12-residue Tir phosphopeptide is sufficient to trigger localized actin assembly.
Enteropathogenic Escherichia coli (EPEC) translocates effector proteins into mammalian cells to promote reorganization of the cytoskeleton into filamentous actin pedestals. One effector, Tir, is a transmembrane receptor for the bacterial surface adhesin intimin, and intimin binding by the extracellular domain of Tir is required for actin assembly. The cytoplasmic NH2 terminus of Tir interacts with focal adhesion proteins, and its tyrosine-phosphorylated COOH terminus binds Nck, a host adaptor protein critical for pedestal formation. To define the minimal requirements for EPEC-mediated actin assembly, Tir derivatives were expressed in mammalian cells in the absence of all other EPEC components. Replacement of the NH2 terminus of Tir with a viral membrane-targeting sequence promoted efficient surface expression of a COOH-terminal Tir fragment. Artificial clustering of this fusion protein revealed that the COOH terminus of Tir, by itself, is sufficient to initiate a complete signaling cascade leading to pedestal formation. Consistent with this finding, clustering of Nck by a 12-residue Tir phosphopeptide triggered actin tail formation in Xenopus egg extracts.
Campellone
Kenneth G
KG
Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Ave. North, Worcester, MA 01655, USA.
Rankin
Susannah
S
Pawson
Tony
T
Kirschner
Marc W
MW
Tipper
Donald J
DJ
Leong
John M
JM
D000185:Actinin / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D018829:Adhesins, Bacterial / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D009419:Nerve Tissue Proteins / Q000378:metabolism; D015513:Oncogene Proteins / Q000378:metabolism*; D009865:Oocytes / Q000502:physiology; D010748:Phosphopeptides / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D014981:Xenopus
D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D018829:Adhesins, Bacterial; D029968:Escherichia coli Proteins; C078332:Nck protein; D009419:Nerve Tissue Proteins; D015513:Oncogene Proteins; D010748:Phosphopeptides; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; C109287:Tir protein, E coli; C495771:WASL protein, human; C495772:Wasl protein, mouse; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D000185:Actinin; C073819:eaeA protein, E coli