title: Specific phosphorylation of proteins in pore complex-laminae from the sponge Geodia cydonium by the homologous aggregation factor and phorbol ester. Role of protein kinase C in the phosphorylation of DNA topoisomerase II.
abstract: We have recently shown that the aggregation factor (AF) from the sponge Geodia cydonium stimulates DNA synthesis in quiescent, dissociated cells from the same organism; this event was correlated with the release of the two second messengers: inositol trisphosphate and diacylglycerol. Here we describe that after binding of the AF to the plasma membrane-bound aggregation receptor, a rapid and drastic increase in the incorporation of 32Pi into a series of proteins in the pore complex-lamina fraction occurs. Addition of the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate, to quiescent cells resulted in a similar stimulation of phosphorylation of nuclear proteins. Among them we have selected one protein with a polypeptide Mr of 170,000 (pp170) for detailed studies. By immunoblotting pp170 was identified as DNA topoisomerase II. In vitro studies with nuclei and purified, homogeneous protein kinase C together with the required activators of this enzyme also showed a phosphorylation of pp170. After phosphorylation, DNA topoisomerase II activity was found to be 2.5-fold that of the non-phosphorylated enzyme. From these data we conclude that protein kinase C is involved in AF induced transmembrane signalling, ultimately leading to an initiation of DNA synthesis.
authors.affiliation: Institut für Physiologische Chemie, Universität, Mainz, FRG.
authors.forename: M
authors.initials: M
authors.lastname: Rottmann
authors.forename: H C
authors.initials: HC
authors.lastname: Schröder
authors.forename: M
authors.initials: M
authors.lastname: Gramzow
authors.forename: K
authors.initials: K
authors.lastname: Renneisen
authors.forename: B
authors.initials: B
authors.lastname: Kurelec
authors.forename: A
authors.initials: A
authors.lastname: Dorn
authors.forename: U
authors.initials: U
authors.lastname: Friese
authors.forename: W E
authors.initials: WE
authors.lastname: Müller
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules; D002449:Cell Aggregation; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D010766:Phosphorylation; D011161:Porifera / Q000166:cytology / Q000201:enzymology*; D011493:Protein Kinase C / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism* / Q000502:physiology*
chemical_list: D015815:Cell Adhesion Molecules; D011506:Proteins; C013065:cell aggregation factors; D011493:Protein Kinase C; D004250:DNA Topoisomerases, Type II