Abstract
Like neutrophilic leukocytes, differentiated HL-60 cells respond to chemoattractant by adopting a polarized morphology, with F-actin in a protruding pseudopod at the leading edge and contractile actin-myosin complexes at the back and sides. Experiments with pharmacological inhibitors, toxins, and mutant proteins show that this polarity depends on divergent, opposing "frontness" and "backness" signals generated by different receptor-activated trimeric G proteins. Frontness depends upon Gi-mediated production of 3'-phosphoinositol lipids (PI3Ps), the activated form of Rac, a small GTPase, and F-actin. G12 and G13 trigger backness signals, including activation of a second GTPase (Rho), a Rho-dependent kinase, and myosin II. Functional incompatibility causes the two resulting actin assemblies to aggregate into separate domains, making the leading edge more sensitive to attractant than the back. The latter effect explains both the neutrophil's ability to polarize in uniform concentrations of chemoattractant and its response to reversal of an attractant gradient by performing a U-turn.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Cell Polarity / physiology*
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Chemotaxis, Leukocyte
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Cytoskeleton / metabolism*
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HL-60 Cells
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Humans
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Models, Biological
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Mutation
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Myosin Type II / metabolism
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N-Formylmethionine Leucyl-Phenylalanine / analogs & derivatives*
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N-Formylmethionine Leucyl-Phenylalanine / pharmacology
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Neutrophils / cytology
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Neutrophils / enzymology
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Neutrophils / physiology*
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Pertussis Toxin / pharmacology
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Phosphoinositide-3 Kinase Inhibitors
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-akt
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Pseudopodia / drug effects
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Recombinant Fusion Proteins / metabolism
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Signal Transduction*
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Transfection
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cdc42 GTP-Binding Protein / drug effects
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cdc42 GTP-Binding Protein / genetics
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cdc42 GTP-Binding Protein / metabolism*
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rac GTP-Binding Proteins / metabolism
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rhoA GTP-Binding Protein / drug effects
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rhoA GTP-Binding Protein / genetics
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rhoA GTP-Binding Protein / metabolism
Substances
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Phosphoinositide-3 Kinase Inhibitors
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Proto-Oncogene Proteins
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Recombinant Fusion Proteins
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N-Formylmethionine Leucyl-Phenylalanine
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formylmethionyl-leucyl-phenylalanine methyl ester
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Pertussis Toxin
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-akt
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Myosin Type II
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cdc42 GTP-Binding Protein
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rac GTP-Binding Proteins
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rhoA GTP-Binding Protein