Armadillo Repeat Containing 8alpha Binds to HRS and Promotes HRS Interaction with Ubiquitinated Proteins.

Recently, we reported that a complex with an essential role in the degradation of Fructose-1,6-bisphosphatase in yeast is well conserved in mammalian cells; we named this mammalian complex C-terminal to the Lissencephaly type-1-like homology (CTLH) complex. Although the function of the CTLH complex remains unclear, here we used yeast two-hybrid screening to isolate Hepatocyte growth factor-regulated tyrosine kinase substrate (HRS) as a protein binding to a key component of CTLH complex, Armadillo repeat containing 8 (ARMc8) alpha. The association was confirmed by a yeast two-hybrid assay and a co-immunoprecipitation assay. The proline-rich domain of HRS was essential for the association. As demonstrated through immunofluorescence microscopy, ARMc8alpha co-localized with HRS. ARMc8alpha promoted the interaction of HRS with various ubiquitinated proteins through the ubiquitin-interacting motif. These findings suggest that HRS mediates protein endosomal trafficking partly through its interaction with ARMc8alpha.