Evidence for pretranslational regulation of collagen synthesis by procollagen propeptides.
We present, here, evidence for a pretranslational role of procollagen propeptides in the regulation of collagen synthesis. Amino- and carboxyl-terminal type I procollagen propeptides were isolated and purified from chick calvaria and tendon cultures. Human lung fibroblasts (IMR-90) were incubated in medium containing varying concentrations of propeptides. Amino-propeptides at 10 nM caused an 80% decrease in collagen synthesis compared to control. Higher concentrations of amino-propeptides did not decrease collagen synthesis further and no significant effect on non-collagen synthesis was found throughout the entire concentration range. Carboxyl-propeptides also inhibited collagen synthesis. At 10 nM, collagen synthesis was decreased by 30% and a concentration of 40 nM caused an 80% reduction. However, at the latter concentration non-collagen synthesis was also affected, decreasing by 20% relative to control. To assess possible pretranslational effects of propeptides, IMR-90 fibroblasts were treated with varying concentrations of each propeptide and levels of type I procollagen mRNA was determined by dot hybridization with a 32P-alpha 2(I) cDNA probe. Both propeptides caused significant concentration-dependent decreases in procollagen type I mRNA levels. At 10 nM, the amino-propeptide resulted in a 55% decrease in collagen mRNA levels while at 40 nM these levels decreased by 72% compared to control. Carboxyl-propeptides were also inhibitory, decreasing mRNA levels by 33% at 10 nM and 73% at 40 nM. Messenger RNA levels of a representative noncollagenous protein, beta-actin, were unaffected by either propeptide throughout the concentration range.
D002460:Cell Line; D003094:Collagen / Q000096:biosynthesis / Q000235:genetics*; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008168:Lung; D009693:Nucleic Acid Hybridization; D011347:Procollagen / Q000502:physiology*; D011392:Proline / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics; D014316:Tritium
D011347:Procollagen; D012333:RNA, Messenger; D014316:Tritium; D003094:Collagen; D011392:Proline