Regulation of lysyl oxidase by basic fibroblast growth factor in osteoblastic MC3T3-E1 cells.
Lysyl oxidase catalyzes the final known enzymatic step required for collagen and elastin cross-linking. A cross-linked collagenous extracellular matrix is required for bone formation. This study investigated whether lysyl oxidase, like its type I collagen substrate, is down-regulated by basic fibroblast growth factor (bFGF) in osteoblastic MC3T3-E1 cells and determined the degree of post-transcriptional control. Steady-state lysyl oxidase mRNA levels decreased to 30% of control after 24 h of treatment with 1 and 10 nm bFGF. This regulation was time-dependent. COL1A1 mRNA levels declined to less than 10% of control after 24 h of bFGF treatment. Media lysyl oxidase activity decreased consistent with steady-state mRNA changes in cultures that were refed after 24 h of growth factor treatment. Interestingly, treatment of MC3T3-E1 cells with 0.01-0.1 nm bFGF for 24 h and treatment with 1 nm bFGF for up to 12 h resulted in a modest stimulation of lysyl oxidase gene expression and enzyme activity. At least 50% of the down-regulation of lysyl oxidase was shown to be posttranscriptional. New protein synthesis was not required for the down-regulation by bFGF, but cycloheximide did increase constitutive lysyl oxidase mRNA levels 2.5-fold. We conclude that lysyl oxidase and COL1A1 are regulated similarly by bFGF in these osteoblastic cells, consistent with the in vivo effects of this growth factor on bone collagen metabolism.
Feres-Filho
E J
EJ
Department of Periodontology and Oral Biology, Boston University Goldman School of Graduate Dentistry, Massachusetts 02118, USA.
Menassa
G B
GB
Trackman
P C
PC
D016475:3T3 Cells; D000818:Animals; D003094:Collagen / Q000235:genetics; D003513:Cycloheximide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D016222:Fibroblast Growth Factor 2 / Q000008:administration & dosage / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects / Q000201:enzymology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D008249:Protein-Lysine 6-Oxidase / Q000235:genetics* / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology
D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D011994:Recombinant Proteins; D016222:Fibroblast Growth Factor 2; D003094:Collagen; D003513:Cycloheximide; D008249:Protein-Lysine 6-Oxidase