A putative receptor mediating cell-density sensing in Dictyostelium.
When Dictyostelium cells starve, they begin secreting a glycoprotein called conditioned medium factor (CMF). When there is a high density of starved cells, as indicated by a high concentration of CMF, the cells begin expressing some genes and aggregate using pulses of cAMP as a chemoattractant. CMF regulates gene expression via a G protein-independent pathway, whereas CMF regulates cAMP signal transduction via a G protein-dependent pathway. To elucidate receptors mediating cell density sensing, we used CMF-Sepharose to isolate membrane proteins that bind CMF. We identified a 50-kDa protein, CMFR1, that is sensitive to trypsin treatment of whole cells. We obtained partial amino acid sequence of CMFR1 and isolated the cDNA encoding it. The derived amino acid sequence has no significant similarity to known proteins and has two or three predicted transmembrane domains. Expression of CMFR1 in insect cells caused an increase in CMF binding. Repression of CMFR1 in Dictyostelium by gene disruption resulted in a approximately 50% decrease of the CMF binding and a loss of CMF-induced G protein-independent gene expression. The G protein-dependent CMF signal transduction pathways appear to be functional in cmfr1 cells, suggesting that cells sense the density-sensing factor CMF using two or more different receptors.
Deery
W J
WJ
Howard Hughes Medical Institute, Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005-1892, USA.
Gomer
R H
RH
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002448:Cell Adhesion / Q000235:genetics; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004023:Dictyostelium / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D015800:Protozoan Proteins; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014357:Trypsin / Q000378:metabolism
D015815:Cell Adhesion Molecules; D018076:DNA, Complementary; D008565:Membrane Proteins; D015800:Protozoan Proteins; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; C052291:cell cohesion molecule, Dictyostelium; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D005982:Glutathione Transferase; D014357:Trypsin; D019204:GTP-Binding Proteins