title: A 60-kilodalton protein component of the counting factor complex regulates group size in Dictyostelium discoideum.
abstract: Much remains to be understood about how a group of cells or a tissue senses and regulates its size. Dictyostelium discoideum cells sense and regulate the size of groups and fruiting bodies using a secreted 450-kDa complex of proteins called counting factor (CF). Low levels of CF result in large groups, and high levels of CF result in small groups. We previously found three components of CF (D. A. Brock and R. H. Gomer, Genes Dev. 13:1960-1969, 1999; D. A. Brock, R. D. Hatton, D.-V. Giurgiutiu, B. Scott, R. Ammann, and R. H. Gomer, Development 129:3657-3668, 2002; and D. A. Brock, R. D. Hatton, D.-V. Giurgiutiu, B. Scott, W. Jang, R. Ammann, and R. H. Gomer, Eukaryot. Cell 2:788-797, 2003). We describe here a fourth component, CF60. CF60 has similarity to acid phosphatases, although it has very little, if any, acid phosphatase activity. CF60 is secreted by starving cells and is lost from the 450-kDa CF when a different CF component, CF50, is absent. Although we were unable to obtain cells lacking CF60, decreasing CF60 levels by antisense resulted in large groups, and overexpressing CF60 resulted in small groups. When added to wild-type cells, conditioned starvation medium from CF60 overexpressor cells as well as recombinant CF60 caused the formation of small groups. The ability of recombinant CF60 to decrease group size did not require the presence of the CF component CF45-1 or countin but did require the presence of CF50. Recombinant CF60 does not have acid phosphatase activity, indicating that the CF60 bioactivity is not due to a phosphatase activity. Together, the data suggest that CF60 is a component of CF, and thus this secreted signal has four different protein components.
authors.affiliation: Howard Hughes Medical Institute, Rice University, 6100 S. Main Street, Houston, Texas 77005-1892, USA.
authors.forename: Debra A
authors.initials: DA
authors.lastname: Brock
authors.forename: Wouter N
authors.initials: WN
authors.lastname: van Egmond
authors.forename: Yousif
authors.initials: Y
authors.lastname: Shamoo
authors.forename: R Diane
authors.initials: RD
authors.lastname: Hatton
authors.forename: Richard H
authors.initials: RH
authors.lastname: Gomer
mesh_terms: D000135:Acid Phosphatase / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D002448:Cell Adhesion / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D016373:DNA, Antisense / Q000235:genetics; D004023:Dictyostelium / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D015870:Gene Expression / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D015800:Protozoan Proteins / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000494:pharmacology
chemical_list: D016373:DNA, Antisense; D015800:Protozoan Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; C120918:countin protein, Dictyostelium discoideum; D000135:Acid Phosphatase