The RGS homology domains of D‐AKAP2 regulate the endocytic recycling compartment through complexes with Rab4 and Rab11

Abstract

Although polymorphisms in D‐AKAP2 (AKAP10) have been linked to morbidity and mortality, heart disease, and breast cancer, the biological function of the protein has remained unknown. In addition to known PKA and PDZ binding motifs at the C‐terminus, D‐AKAP2 contains two Regulator of G‐protein signaling Homology (RH) domains with no known interacting partners. We have shown that the RH domains can localize the protein to the endocytic recycling compartment. Co‐expression of D‐AKAP2 with GFP‐tagged Rab4 or Rab11, but not Rab5 or Rab7, causes recruitment of D‐AKAP2 from the cytosol and enlargement of endosomal structures that are accessible to endocytosed transferrin. Flag‐tagged D‐AKAP2 can co‐immunoprecipitate the wild‐type and GTP‐locked mutants of Rab4 and Rab11, but not GDP‐locked mutants or Rab5. A yeast two‐hybrid screen identified the gamma subunit of the AP‐1 clathrin adaptor protein complex as an interacting partner, and we have confirmed this with co‐immunoprecipitation and in vitro GST pull‐down studies. Receptor trafficking experiments with overexpressed and knocked‐down D‐AKAP2 suggest that it may act as a Rab effector regulating the recycling of membrane proteins.