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Mullerian inhibiting substance binding and uptake
E A Catlin1, R M Ezzell, P K Donahoe
1Division of Neonatal and Pediatric Intensive Care, Massachusetts General Hospital, Boston 02114.
Abstract:
Mullerian inhibiting substance (MIS) is a 140,000 M(r) Sertoli cell derived glycoprotein with a critical regulatory role in the male fetus initiated presumably by ligand binding with receptor. To localize this binding species we performed time course incubations of cultured fetal rat lungs or control tissues with MIS, applied rabbit anti-MIS IgG, and fluorescein conjugated anti-rabbit IgG, and examined specimens with laser confocal microscopy. Punctate surface fluorescence followed by cytosolic and nuclear localization in lung consistent with specific adsorptive endocytosis was seen. Confocal imaging also detected MIS binding to the Mullerian duct in the urogenital ridge. Crosslinking of 125I-MIS with plasma membranes revealed a high molecular mass binder with signal displaceable by excess unlabeled ligand. These data support the hypothesis that a specific plasma membrane binding protein for MIS exists.
Insights
Mullerian inhibiting substance (MIS) binds to a specific protein on the cell surface, initiating its function in male fetal development. This binding is crucial for understanding MIS action and potential therapeutic targets.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Endocrinology
Background:
- Mullerian inhibiting substance (MIS) is a glycoprotein from Sertoli cells.
- MIS plays a critical role in male fetal development.
- Its function is presumed to be initiated by ligand-receptor binding.
Purpose of the Study:
- To identify and localize the binding species for MIS.
- To investigate the mechanism of MIS action in fetal tissues.
Main Methods:
- Incubation of cultured fetal rat lungs and urogenital ridge tissues with MIS.
- Immunofluorescence labeling using anti-MIS IgG and fluorescein-conjugated secondary antibodies.
- Laser confocal microscopy for visualization.
- Crosslinking of 125I-MIS with plasma membranes.
Main Results:
- Punctate surface fluorescence followed by cytosolic and nuclear localization in lung tissue, suggesting adsorptive endocytosis.
- MIS binding was observed on the Mullerian duct in the urogenital ridge.
- Plasma membrane crosslinking identified a high molecular mass MIS binder, displaceable by unlabeled MIS.
Conclusions:
- A specific plasma membrane binding protein for MIS exists.
- These findings support the hypothesis of a specific receptor mediating MIS function.
- The study provides insights into the cellular mechanisms of MIS action during male development.