The small GTPase Arl8b regulates assembly of the mammalian HOPS complex on lysosomes

J Cell Sci. 2015 May 1;128(9):1746-61. doi: 10.1242/jcs.162651. Epub 2015 Apr 23.


The homotypic fusion and protein sorting (HOPS) complex is a multi-subunit complex conserved from yeast to mammals that regulates late endosome and lysosome fusion. However, little is known about how the HOPS complex is recruited to lysosomes in mammalian cells. Here, we report that the small GTPase Arl8b, but not Rab7 (also known as RAB7A), is essential for membrane localization of the human (h)Vps41 subunit of the HOPS complex. Assembly of the core HOPS subunits to Arl8b- and hVps41-positive lysosomes is guided by their subunit-subunit interactions. RNA interference (RNAi)-mediated depletion of hVps41 resulted in the impaired degradation of EGFR that was rescued upon expression of wild-type but not an Arl8b-binding-defective mutant of hVps41, suggesting that Arl8b-dependent lysosomal localization of hVps41 is required for its endocytic function. Furthermore, we have also identified that the Arl8b effector SKIP (also known as PLEKHM2) interacts with and recruits HOPS subunits to Arl8b and kinesin-positive peripheral lysosomes. Accordingly, RNAi-mediated depletion of SKIP impaired lysosomal trafficking and degradation of EGFR. These findings reveal that Arl8b regulates the association of the human HOPS complex with lysosomal membranes, which is crucial for the function of this tethering complex in endocytic degradation.

Keywords: Arl8b; Lysosome; Mammalian HOPS complex; SKIP; hVps41.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ADP-Ribosylation Factors / chemistry
  • ADP-Ribosylation Factors / metabolism*
  • Adaptor Proteins, Signal Transducing / metabolism
  • Animals
  • Autophagy-Related Proteins
  • Cell Membrane / metabolism
  • Endocytosis
  • ErbB Receptors / metabolism
  • Guanosine Triphosphate / metabolism
  • HeLa Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Lysosomes / metabolism*
  • Mammals / metabolism*
  • Multiprotein Complexes / metabolism*
  • Polymorphism, Single Nucleotide / genetics
  • Protein Binding
  • Protein Structure, Tertiary
  • Protein Subunits / metabolism
  • Protein Transport
  • Proteolysis
  • Vesicular Transport Proteins / genetics
  • Vesicular Transport Proteins / metabolism


  • ARL8B protein, human
  • Adaptor Proteins, Signal Transducing
  • Autophagy-Related Proteins
  • Intracellular Signaling Peptides and Proteins
  • Multiprotein Complexes
  • Protein Subunits
  • SPHKAP protein, human
  • VPS39 protein, human
  • VPS41 protein, human
  • Vesicular Transport Proteins
  • Guanosine Triphosphate
  • ErbB Receptors
  • ADP-Ribosylation Factors