Several weak signals in the cytosolic and transmembrane domains of the interleukin-2-receptor beta chain allow for its efficient endocytosis.

Plasma membrane receptors are retrieved continually from the cell surface by endocytosis and transported to intracellular organelles. They are internalized at various rates depending on their ability to interact with endocytic structures of the plasma membrane. The interleukin-2-receptor beta chain is endocytosed constitutively and efficiently. Here we show that different motifs in its cytosolic tail promote entry in an additive way, each of them acting as a weak internalization signal. The transmembrane domain of beta also participates in endocytosis. In conclusion, several weak endocytic determinants can be responsible for the rapid internalization of a membrane protein.