G protein signaling events are activated at the leading edge of chemotactic cells.
Directional sensing by eukaryotic cells does not require polarization of chemoattractant receptors. The translocation of the PH domain-containing protein CRAC in D. discoideum to binding sites on the inner face of the plasma membrane reflects activation of the G protein-linked signaling system. Increments in chemoattractant elicit a uniform response around the cell periphery. Yet when cells are exposed to a gradient, the activation occurs selectively at the stimulated edge, even in immobilized cells. We propose that such localized activation, transmitted by the recruitment of cytosolic proteins, may be a general mechanism for gradient sensing by G protein-linked chemotactic systems including those involving chemotactic cytokines in leukocytes.
Parent
C A
CA
Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Blacklock
B J
BJ
Froehlich
W M
WM
Murphy
D B
DB
Devreotes
P N
PN
D000818:Animals; D001665:Binding Sites; D001692:Biological Transport; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism; D002630:Chemotactic Factors / Q000494:pharmacology; D002633:Chemotaxis; D000242:Cyclic AMP / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D004023:Dictyostelium; D019204:GTP-Binding Proteins / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D006863:Hydrogen-Ion Concentration; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
D002630:Chemotactic Factors; D008164:Luminescent Proteins; D015800:Protozoan Proteins; C089420:dagA protein, Dictyostelium; D049452:Green Fluorescent Proteins; D000242:Cyclic AMP; D019204:GTP-Binding Proteins