Mechanistic Studies of Membrane Remodeling in Receptor Mediated Endocytosis

Abstract

Receptor mediated endocytosis requires the generation of membrane curvature. Followed by external stimulation, various G-protein coupled receptors and epidermal growth factor receptors are internalized and recycled by this crucial membrane trafficking pathway. Bin/Amphiphysin/RVS (BAR) superfamily proteins have emerged as key effectors in membrane reshaping during the endocytic events. In addition to a crescent shaped BAR domain, many of these proteins contain a Src homology 3 (SH3) domain. BAR proteins sense and generate membrane curvature with their membrane binding domain whereas the SH3 domain regulates their interaction with other protein binding partners. Receptors containing proline rich domains (PRD) have been found to interact with different classes of SH3 domain containing proteins. While it has been hypothesized that the SH3 domain-PRD interaction plays an important role in BAR protein mediated receptor internalization, the exact mechanism has thus far remained elusive. We mimic SH3 domain-PRD interactions in artificial lipid bilayers and investigate their effects on the characteristic membrane curvature generation properties of BAR proteins. PRDs covalently linked to the lipid bilayer are designed to recruit the BAR proteins. The associated membrane shape changes are monitored by both optical and electron microscopy. Insights into BAR protein mediated membrane remodeling in receptor internalization processes from these biophysical studies will be discussed in this contribution.