Receptor Mediated Endocytosis 8 Utilizes an N-terminal Phosphoinositide Binding Motif to Regulate Endosomal Clathrin Dynamics [Signal Transduction]

July 1st, 2015 by Xhabija, B., Vacratsis, P. O.

Receptor mediated endocytosis 8 (RME-8) is a DnaJ domain containing protein implicated in translocation of Hsc70 to early endosomes for clathrin removal during retrograde transport. Previously, we have demonstrated that RME-8 associates with early endosomes in a PI(3)P dependent fashion. In this study we have now identified amino acid determinants required for PI(3)P binding within a region predicted to adopt a pleckstrin-homology like fold in the N-terminus of RME-8. The ability of RME-8 to associate with PI(3)P and early endosomes is largely abolished when residues Lys17, Trp20, Tyr24, or Arg26 are mutated resulting in diffuse cytoplasmic localization of RME-8 while maintaining the ability to interact with Hsc70. We also provide evidence that RME-8 PI(3)P binding regulates early endosomal clathrin dynamics and alters the steady state localization of the cation-independent mannose 6-phosphate receptor. Interestingly, RME-8 endosomal association is also regulated by the PI(3)P binding protein SNX1, a member of the retromer complex. Wild type SNX1 restores endosomal localization of RME-8 W20A while a SNX1 variant deficient in PI(3)P binding disrupts endosomal localization of wild type RME-8. These results further highlight the critical role for PI(3)P in the RME-8 mediated organizational control of various endosomal activities including retrograde transport.
  • Posted in Journal of Biological Chemistry, Publications
  • Comments Off on Receptor Mediated Endocytosis 8 Utilizes an N-terminal Phosphoinositide Binding Motif to Regulate Endosomal Clathrin Dynamics [Signal Transduction]