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Internalization of insulin: structures involved and significance
Advances in Experimental Medicine and Biology
|January 1, 1985
Summary
Insulin binds its receptor, leading to cell internalization. Endosomes sort these complexes, directing insulin to lysosomes and receptors for reuse, potentially initiating insulin action.
Area of Science:
- Cell biology
- Endocrinology
- Molecular signaling
Background:
- Insulin receptor binding triggers hormone-receptor complex internalization.
- Internalized complexes aggregate and concentrate in endocytotic structures, distinct from lysosomes.
- These structures are heterogeneous and involved in sorting and dissociation.
Purpose of the Study:
- To elucidate the role of endosomes in insulin internalization and signaling.
- To characterize the endosomal apparatus involved in hormone-receptor complex processing.
- To investigate potential initiation of insulin action within endosomes.
Main Methods:
- Cellular internalization studies using insulin and its receptor.
- Centrifugation techniques to resolve endocytotic structures.
- Biochemical assays to identify Golgi elements and receptor kinase activity.
Main Results:
- Internalized insulin-receptor complexes concentrate in Golgi-enriched endosomes, not lysosomes.
- Endocytotic structures can be separated from Golgi elements.
- Endosomes exhibit insulin-stimulable receptor kinase activity.
Conclusions:
- Endosomes function as a sorting center for internalized insulin-receptor complexes.
- Hormone is directed to lysosomes, while receptors are recycled to the cell surface.
- Insulin action may be initiated within endosomal compartments due to identified kinase activity.