All living cells are strictly separated from their surroundings by a membranous lipid bilayer. Into these membranes a variety of transport proteins are embedded that ensure the uptake and secretion of various molecules and ions. In order to respond properly to a changing nutrient supply or demand, as well as to external stress factors, cells must be able to adapt both amount and activity of the corresponding transporters. This book provides readers with state-of-the-art knowledge on the various regulatory mechanisms that control transmembrane transporter expression, activity and their subcellular localisation.