Expression and properties of the Rab4, Rabaptin-5alpha, AP-1 complex in endosomal recycling.

We previously showed that the small GTPase Rab4 regulates formation of recycling vesicles from early endosomes. To understand how Rab4 accomplishes this task, we started to identify the Rab4 effector protein network. In this chapter, we describe experiments leading to the characterization of a complex consisting of Rab4GTP, its effector Rabaptin-5alpha, and the adaptor protein complex AP-1, which regulates recycling from endosomes.

Rabip4' is an effector of rab5 and rab4 and regulates transport through early endosomes.

We describe the characterization of an 80-kDa protein cross-reacting with a monoclonal antibody against the human La autoantigen. The 80-kDa protein is a variant of rabip4 with an N-terminal extension of 108 amino acids and is expressed in the same cells. For this reason, we named it rabip4'.