Clathrin Heavy Chain Expression and Subcellular Distribution in Embryos of Drosophila melanogaster

Tubular organs are essential for organisms to establish transport systems for nutrients, liquids and gases. The development of tubes requires endocytosis of bound ligands, receptors and proteins at the plasma membrane (Bonifacino and Traub, 2003; Nelson, 2009). Clathrin coated vesicles (CCVs) organize major routes of cargo selective endocytosis in higher eukaryotic cells (Conner and Schmid, 2003). The formation of CCVs requires clathrin molecules. During CCV budding, clathrin molecules assemble to form a cage-like coat around the nascent vesicle membrane. Clathrin assembly is assisted by numerous adaptor proteins. After inward budding, CCV scission from the membrane is mediated by the large GTPase Dynamin. Released CCVs diffuse from the membrane and undergo uncoating, whereby Clathrin molecules disassemble from the vesicles. The uncoating process is mediated by the ATPase function of the Heat shock cognate protein (Hsc70), which interacts with Chc and DnaJ adaptor proteins. The released Clathrin molecules reassemble for subsequent rounds of endocytosis while vesicles fuse with acceptor compartments, such as early endosomes (Conner and Schmid, 2003; Kirchhausen, 2000; Ungewickell and Hinrichsen, 2007).