Soluble collagen VI drives serum-starved fibroblasts through S phase and prevents apoptosis via down-regulation of Bax.
We previously showed that soluble, pepsin-solubilized collagen VI increases de novo DNA synthesis in serum-starved HT1080 and 3T3 fibroblasts up to 100-fold compared with soluble collagen I, reaching 80% of the stimulation caused by 10% fetal calf serum. Here we show that collagen VI also inhibits apoptotic cell death in serum-starved cells as evidenced by morphological criteria, DNA laddering, complementary apoptosis assays (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, enzyme-linked immunosorbent assay, and fluorescence-activated cell sorting), and quantification of apoptosis-regulating proteins. In the presence of starving medium alone or collagen I, the proapoptotic Bax was up-regulated 2-2.5-fold, compared with soluble collagen VI and fetal calf serum, whereas levels of the antiapoptotic Bcl-2 protein remained unaffected. In accordance with its potent stimulation of DNA synthesis, soluble collagen VI carries serum-starved HT1080 and Balb 3T3 fibroblasts through G(2) as shown by fluorescence-activated cell sorting analysis, whereas cells exposed to medium and collagen I where arrested at G(1)-S. This was accompanied by a 2-3-fold increase in cyclin A, B, and D1 protein expression. Collagen VI-induced inhibition of apoptotic cell death may be operative during embryogenesis, wound healing, and fibrosis when elevated tissue and blood levels of collagen VI are observed, thus initiating a feedback loop of mesenchymal cell activation and proliferation.
Rühl
M
M
Department of Medicine I, Klinikum B. Franklin, Free University of Berlin, Hindenburgdamm 30, 12200 Berlin, Germany.
Sahin
E
E
Johannsen
M
M
Somasundaram
R
R
Manski
D
D
Riecken
E O
EO
Schuppan
D
D
D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002448:Cell Adhesion / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003094:Collagen / Q000494:pharmacology*; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D019925:Cyclin A / Q000187:drug effects / Q000378:metabolism; D019926:Cyclin B / Q000187:drug effects / Q000378:metabolism; D019938:Cyclin D1 / Q000187:drug effects / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D015536:Down-Regulation; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D020287:In Situ Nick-End Labeling; D019012:Integrin beta1 / Q000502:physiology; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000187:drug effects* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D016196:S Phase; D012995:Solubility; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; C494827:Bax protein, mouse; D016895:Culture Media, Serum-Free; D019925:Cyclin A; D019926:Cyclin B; D019012:Integrin beta1; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D019938:Cyclin D1; D003094:Collagen