ADAM-9 is an insulin-like growth factor binding protein-5 protease produced and secreted by human osteoblasts.
IGF binding protein-5 (BP-5) is an important bone formation regulator. Therefore, elucidation of the identity of IGF binding protein-5 (BP-5) protease produced by osteoblasts is important for our understanding of the molecular pathways that control the action of BP-5. In this regard, BP-5 protease purified by various chromatographic steps from a conditioned medium of U2 human osteosarcoma cells migrated as a single major band, which comigrated with the protease activity in native PAGE and yielded multiple bands in SDS-PAGE under reducing conditions. N-Terminal sequencing of these bands revealed that three of the bands yielded amino acid sequences that were identical to that of alpha2 macroglobulin (alpha2M). Although alpha2M was produced by human osteoblasts (OBs), it was not found to be a BP-5 protease. Because alpha2M had been shown to complex with ADAM proteases and because ADAM-12 was found to cleave BP-3 and BP-5, we evaluated if one of the members of ADAM family was the BP-5 protease. On the basis of the findings that (1) purified preparations of BP-5 protease from U2 cell CM contained ADAM-9, (2) ADAM-9 is produced and secreted in high abundance by various human OB cell types, (3) purified ADAM-9 cleaved BP-5 effectively while it did not cleave other IGFBPs or did so with less potency, and (4) purified ADAM-9 bound to alpha2M, we conclude that ADAM-9 is a BP-5 protease produced by human OBs.
Mohan
Subburaman
S
Musculoskeletal Diseases Center, Jerry L. Pettis VA Medical Center, 11201 Benton Street, Loma Linda, California 92357, USA. mohans@lom.med.va.gov
Thompson
Garrett R
GR
Amaar
Yousef G
YG
Hathaway
Gary
G
Tschesche
Harald
H
Baylink
David J
DJ
D051722:ADAM Proteins; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D019483:Disintegrins; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000378:metabolism*; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D008666:Metalloendopeptidases / Q000096:biosynthesis* / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D009124:Muscle Proteins / Q000096:biosynthesis* / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D010006:Osteoblasts / Q000201:enzymology* / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D011485:Protein Binding; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D020539:Sequence Analysis, Protein; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured; D000511:alpha-Macroglobulins / Q000096:biosynthesis / Q000737:chemistry
D019483:Disintegrins; D018975:Insulin-Like Growth Factor Binding Protein 5; D008565:Membrane Proteins; D009124:Muscle Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D000511:alpha-Macroglobulins; D051722:ADAM Proteins; C098339:ADAM9 protein, human; D008666:Metalloendopeptidases