Antibody-feeding assay: A method to track the internalization of neuropilin-1 and other cell surface receptors

Ligand-induced endocytosis of receptors exposed on the plasma membrane is a fundamental regulatory step for their functional activation and interaction with intracellular signal transducers. Thus, elucidating the timing of endocytosis and tracing the intracellular fate of receptors is instrumental to understand their signaling cascade in different conditions. Here we describe an assay for the study of endocytosis and intracellular trafficking of individual surface receptors, in living cells subject to different experimental challenges. We applied this method for studying the functional interaction between semaphorin coreceptor Neuropilin-1 and a tyrosine kinase receptor exposed on the cell surface.