Role of ER export signals in controlling surface potassium channel numbers

Little is known about the identity of endoplasmic reticulum (ER) export sig nals and how they are used to regulate the number of proteins on the cell s urface. Here, we describe two ER export signals that profoundly altered the steady-state distribution of potassium channels and were required for chan nel localization to the plasma membrane. When transferred to other potassiu m channels or a G protein-coupled receptor, these ER export signals increas ed the number of functional proteins on the cell surface. Thus, ER export o f membrane proteins is not necessarily limited by folding or assembly, but may be under the control of specific export signals.