Mutations in human dynamin block an intermediate stage in coated vesicle formation

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Receptor-mediated endocytosis is a vital cellular process for nutrient uptake and signal transduction.
• Dynamin, a GTPase, is implicated in various membrane trafficking events, including endocytosis.
• The precise role of dynamin's GTP-binding domain in endocytosis remains to be fully elucidated.

Purpose of the Study:

• To investigate the function of human dynamin in receptor-mediated endocytosis.
• To determine the specific stage of endocytosis affected by dynamin GTP-binding domain mutants.
• To assess the necessity of a functional dynamin GTPase for clathrin-coated pit-mediated endocytosis.

Main Methods:

• Transient expression of GTP-binding domain mutants of human dynamin in mammalian cells.
• Utilizing assays to detect intermediates in coated vesicle formation.
• Monitoring transferrin (Tfn) endocytosis and membrane transport from the ER to the Golgi.

Main Results:

• Dynamin mutants blocked endocytosis after coat assembly initiation but before ligand sequestration.
• The observed blockage occurred specifically in early endocytic events.
• Membrane transport from the ER to the Golgi remained unaffected, indicating specificity.
• Mutations in the dynamin GTP-binding domain inhibited transferrin endocytosis.

Conclusions:

• A functional dynamin GTPase is essential for receptor-mediated endocytosis via clathrin-coated pits.
• Mutations in the dynamin GTP-binding domain disrupt early stages of endocytosis.
• Dynamin plays a critical role in the scission of coated vesicles during endocytosis.