Tumor suppressive effect of lysyl oxidase proenzyme.
Lysyl oxidase acts as both a matrix modifying enzyme and an oncogene suppressor. It is synthesized as a 50-kDa proenzyme, secreted, and processed into an approximately 30 kDa mature, active enzyme and an 18-kDa propeptide. The tumor suppressive effect of lysyl oxidase appears to be exerted within the cell, so the subcellular localization of protein forms was investigated. Propeptide-specific antibody detected 50-kDa proenzyme in cytoplasmic and nuclear extracts of non-transformed mouse fibroblasts, but free 18-kDa propeptide was not detected in any extract. Antibody to epitope near the N-terminus of mature lysyl oxidase detected the proenzyme product in non-transformed cells, and a 30-kDa cytoplasmic protein in both non-transformed and transformed cells. RNA interference reduced the expression of lysyl oxidase mRNA and 50-kDa proenzyme in non-transformed cells, but had no effect on 30-kDa protein, indicating that although this protein displays a lysyl oxidase epitope, it is not derived from lysyl oxidase message. The absence of both free 18-kDa propeptide and mature lysyl oxidase within non-transformed cells suggests that cellular reversion after restoration of lysyl oxidase gene expression is mediated by the 50-kDa proenzyme within cells.
Department of Pathology, United States Military Cancer Institute, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA. scontente@usuhs.mil
Sara
S
Contente
Tze-Jou Annie
TJ
Yeh
Robert M
RM
Friedman
D000818:Animals; D002461:Cell Line, Transformed; D004622:Embryo, Mammalian / Q000166:cytology / Q000201:enzymology*; D004792:Enzyme Precursors / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology*; D015151:Immunoblotting; D051379:Mice; D041681:NIH 3T3 Cells; D010446:Peptide Fragments / Q000276:immunology; D014176:Protein Biosynthesis; D008249:Protein-Lysine 6-Oxidase / Q000378:metabolism*; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D004792:Enzyme Precursors; D010446:Peptide Fragments; D025521:Tumor Suppressor Proteins; D008249:Protein-Lysine 6-Oxidase