Clathrin is used in :

Receptor mediated endocytosis is a process by which cells internalize receptor bound ligands. Clathrin mediated endocytosis is so far the best characterized pathway by which cells internalize specific molecules and modulate the expression level of membrane bound receptors. Clathrin-mediated endocytosis occurs at membrane indentations where the protein clathrin accumulates. It has shape of triskelions, with three legs radiating from a central hub. Clathrin-mediated endocytosis is responsible for the internalization of many receptors and the ligands bound to them. Eg nerve growth factor and LDL. It also plays a major role in synaptic function. Ref: Nanopaiculate Drug Delivery Systems: Strategies, Technologies, and ... edited by Yoon Yeo, Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 2. Overview of Cellular Physiology in Medical Physiology. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.