title: Differential up-regulation of Rap1a and Rap1b proteins during smooth muscle cell cycle.
abstract: The relationship between Rap1 proteins and cell proliferation was assessed by investigating the effect of isoforms AA and BB of platelet-derived growth factor (PDGF) on Rap1 protein and mRNA expression throughout the smooth muscle cell cycle. Firstly, PDGF BB-induced cell cycle traverse was studied, thus demonstrating entry into S phase at 18 to 20 h. Western blotting carried out on total Rap1 proteins showed that 5 ng/ml of PDGF BB instigated a biphasic induction of total Rap1 proteins during the cell cycle. This involved a 2.1 +/- 0.4-fold increase at 6 h (early G1) and a 2.8 +/- 0.6-fold increase at 20 to 24 h (G1/S transition). Such an up-regulation was abolished by addition of 1 ng/ml of transforming growth factor-beta 1 (TGF-beta 1), which inhibited up to 80% of the PDGF BB-induced entry into S phase. Comparative RT-PCR of both rap1a and rap1b mRNAs throughout the cell cycle allowed us to differentiate between the two rap1a and rap1b species. PDGF BB induced a 1.9 +/- 0.3-fold increase at 4 h and a 2.4 +/- 0.2-fold relative increase at 16 h for rap1b mRNA, whereas a unique 1.9 +/- 0.5-fold increase in rap1a mRNA was observed at 14 h. Again, this induction of rap1a and rap1b mRNAs by PDGF BB was totally abolished by TGF-beta 1. We conclude that the differential up-regulation of Rap1a and Rap1b proteins during the smooth muscle cell cycle is directly linked to cell proliferation.
authors.affiliation: INSERM U 348, IFR Circulation Lariboisière, Hôpital Lariboisière, Paris/France.
authors.forename: R
authors.initials: R
authors.lastname: Quarck
authors.forename: E
authors.initials: E
authors.lastname: Berrou
authors.forename: C
authors.initials: C
authors.lastname: Magnier
authors.forename: R
authors.initials: R
authors.lastname: Bobe
authors.forename: R
authors.initials: R
authors.lastname: Bredoux
authors.forename: G
authors.initials: G
authors.lastname: Tobelem
authors.forename: J
authors.initials: J
authors.lastname: Enouf
authors.forename: M
authors.initials: M
authors.lastname: Bryckaert
mesh_terms: D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology; D001011:Aorta / Q000166:cytology; D000077214:Becaplermin; D015139:Blotting, Southern; D002453:Cell Cycle / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D007700:Kinetics; D009131:Muscle, Smooth, Vascular / Q000737:chemistry* / Q000166:cytology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger / Q000378:metabolism; D016196:S Phase / Q000187:drug effects / Q000235:genetics; D013552:Swine; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D015854:Up-Regulation / Q000502:physiology; D020668:rap GTP-Binding Proteins
chemical_list: D000925:Anticoagulants; D010982:Platelet-Derived Growth Factor; D011518:Proto-Oncogene Proteins; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; C075278:platelet-derived growth factor A; D000077214:Becaplermin; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins