title: Expression of the contact site A glycoprotein in Dictyostelium discoideum: quantitation and developmental regulation.
abstract: We have previously reported that a monoclonal antibody directed specifically against a surface glycoprotein of Mr 80,000 (gp80) inhibits the EDTA-resistant contact sites A of Dictyostelium discoideum (Siu, C.-H., and Choi, A.H.C. (1985) J. Biol. Chem. 260, 16030-16036). In this report, we describe an assay using this monoclonal antibody to quantitate the amount of gp80 expressed at different developmental stages. Under normal conditions, gp80 is detectable after 6 h of development and it rapidly accumulates between 6 and 10 h, corresponding to the time when cells acquire their EDTA-resistant binding sites. At the peak level, there are 1.5.10(5) gp80 molecules per cell. More than 90% of the cellular gp80 is located on the cell surface. When cells are given exogenous pulses of cAMP, a precocious and enhanced expression of gp80 is induced. At the peak level, the cAMP-pulsed cells accumulate five times more gp80 than the non-pulsed cells. This is preceeded by an equally rapid accumulation of gp80 transcripts, suggesting that cAMP regulates gp80 synthesis at the transcriptional level.
authors.affiliation: Banting and Best Department of Medical Research, University of Toronto, Ontario, Canada.
authors.forename: C H
authors.initials: CH
authors.lastname: Siu
authors.forename: T Y
authors.initials: TY
authors.lastname: Lam
authors.forename: L M
authors.initials: LM
authors.lastname: Wong
mesh_terms: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface / Q000032:analysis / Q000096:biosynthesis* / Q000276:immunology; D015815:Cell Adhesion Molecules; D002450:Cell Communication; D002462:Cell Membrane / Q000032:analysis / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology; D004023:Dictyostelium / Q000032:analysis / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D008562:Membrane Glycoproteins / Q000032:analysis / Q000096:biosynthesis* / Q000276:immunology; D009693:Nucleic Acid Hybridization; D015800:Protozoan Proteins; D012331:RNA, Fungal / Q000032:analysis; D014158:Transcription, Genetic
chemical_list: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D015815:Cell Adhesion Molecules; D008562:Membrane Glycoproteins; D015800:Protozoan Proteins; D012331:RNA, Fungal; C052291:cell cohesion molecule, Dictyostelium; D000242:Cyclic AMP