Abstract
The characterization and regulation of IGFBPs in TM-3 cells was performed. Western Ligand blots of conditioned media(CM) demonstrated the presence of 24 and 28 kDa bands as major IGFBPs, and 40 and 44 kDa as minor ones. The 24 and 28 kDa bands were immunoprecipitated with an antibody to rat IGFBP-4. The 28 kDa band was deglycosylated with endoglycosidase-F to 24 kDa.
Treatment of TM-3 cells with IGF-I increased the levels of IGFBP-4. Both IGF-II and [Leu27] IGF-II treatment resulted in a significant decrease in IGFBP-4. Neither IGF-I nor -II affected the expression of mRNA for IGFBP-4. Affinity cross-linking of IGF-I and -II to crude membranes prepared from TM-3 cells revealed type 1 and 2 receptors and a 31 kDa band. Immunoprecipitation of solubllized crude membranes Indicated that the 31 kDa protein was membrane bound IGFBP-4. In conclusion, TM-3 cells can produce IGFBP-4 and glycosylated IGFBP-4 as major IGFBPs. A unique divergent effect of IGF-I and -II on the levels of IGFBP-4 In CM must be posttranscriptional and occur through different mechanism. The significance of the presence of IGFBP-4 In CM and membrane bound IGFBP-4 should be elucidated.
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Hasegawa, T., Cohen, P., Fielder, P. et al. CHARACTERIZATION AND REGULATION OF IGFBP-4 IN CULTURED MOUSE LEYDIG CELLS (TM-3). Pediatr Res 33 (Suppl 5), S43 (1993). https://doi.org/10.1203/00006450-199305001-00238
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DOI: https://doi.org/10.1203/00006450-199305001-00238
