Membrane proteins are major sensors of extracellular stimuli and initiators of intracellular signal transduction, and their abundance on the cell surface in particular is often dynamically regulated even when there are no significant changes of their total abundance in a cell. This protocol is designed to biochemically label and separate membrane proteins on the plasma membrane from those in the intracellular compartments. In conjunction with co-immunoprecipitation and western blot analysis, functional analysis of dynamic interaction of membrane proteins with other membrane proteins or intracellular adaptor and effector proteins can be achieved.