Autocrine motility factor stimulates a three-fold increase in inositol trisphosphate in human melanoma cells.
The biochemical pathways through which tumor cell locomotion is mediated are poorly understood. Autocrine motility factor (AMF), which is produced by and stimulates motility in A2058 human melanoma cells, was used to characterize phosphoinositide (PtdIns) metabolism activated in association with tumor cell motility. AMF stimulated up to a 400% increase in de novo incorporation of 3H-myo-inositol into cellular lipids beginning 40 minutes after exposure. In cells prelabeled with 3H-myo-inositol, AMF stimulated a 200% increase in total inositol phosphates (inositol monophosphate, InsP1; inositol bisphosphate, InsP2; inositol trisphosphate, InsP3) after 90 minutes of exposure, with a 300% maximal increase in InsP3 at 120 minutes. InsP1 and InsP2 were maximally increased 130% of control values. Treatment with AMF stimulated a parallel dose-dependent increase in both motility and PtdIns levels. We have shown previously that the A2058 motile response to AMF is inhibited markedly by cell pretreatment with pertussis toxin (PT). Inositol phosphate production was inhibited by a 2-hour pretreatment of cells with PT (0.5 microgram/ml). PT treatment of A2058 membranes was associated with ADP-ribosylation of a 40-kDa protein consistent with the presence of an alpha subunit of a guanine nucleotide-binding protein (G protein). These data indicate that AMF elicits increases in cell motility and phosphoinositide metabolism via a PT-sensitive G protein signal transduction pathway.
Kohn
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EC
Medicine Branch, National Cancer Institute, National Institute of Health, Bethesda, MD 20892.
Liotta
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LA
Schiffmann
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D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D002465:Cell Movement; D019204:GTP-Binding Proteins / Q000378:metabolism; D005956:Glucose-6-Phosphate Isomerase; D006801:Humans; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000378:metabolism*; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology; D008565:Membrane Proteins / Q000378:metabolism; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000494:pharmacology*; D037342:Pertussis Toxin; D010716:Phosphatidylinositols / Q000378:metabolism*; D015398:Signal Transduction; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D007295:Inositol Phosphates; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D010716:Phosphatidylinositols; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D005956:Glucose-6-Phosphate Isomerase