Phosphatidylinositol-4-kinase type II alpha contains an AP-3-sorting motif and a kinase domain that are both required for endosome traffic

Mol Biol Cell. 2008 Apr;19(4):1415-26. doi: 10.1091/mbc.e07-12-1239. Epub 2008 Feb 6.

Abstract

The adaptor complex 3 (AP-3) targets membrane proteins from endosomes to lysosomes, lysosome-related organelles and synaptic vesicles. Phosphatidylinositol-4-kinase type II alpha (PI4KIIalpha) is one of several proteins possessing catalytic domains that regulate AP-3-dependent sorting. Here we present evidence that PI4KIIalpha uniquely behaves both as a membrane protein cargo as well as an enzymatic regulator of adaptor function. In fact, AP-3 and PI4KIIalpha form a complex that requires a dileucine-sorting motif present in PI4KIIalpha. Mutagenesis of either the PI4KIIalpha-sorting motif or its kinase-active site indicates that both are necessary to interact with AP-3 and properly localize PI4KIIalpha to LAMP-1-positive endosomes. Similarly, both the kinase activity and the sorting signal present in PI4KIIalpha are necessary to rescue endosomal PI4KIIalpha siRNA-induced mutant phenotypes. We propose a mechanism whereby adaptors use canonical sorting motifs to selectively recruit a regulatory enzymatic activity to restricted membrane domains.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Motifs
  • Animals
  • Base Sequence
  • Binding Sites / genetics
  • Catalytic Domain / genetics
  • Cell Line
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Endosomes / metabolism*
  • Humans
  • Lysosomal Membrane Proteins / metabolism
  • Minor Histocompatibility Antigens
  • Multiprotein Complexes
  • Mutagenesis, Site-Directed
  • PC12 Cells
  • Phosphotransferases (Alcohol Group Acceptor) / antagonists & inhibitors
  • Phosphotransferases (Alcohol Group Acceptor) / chemistry*
  • Phosphotransferases (Alcohol Group Acceptor) / genetics
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Protein Structure, Tertiary
  • RNA, Small Interfering / genetics
  • Rats
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Transcription Factors / chemistry
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Transfection

Substances

  • DNA-Binding Proteins
  • LAMP1 protein, human
  • Lysosomal Membrane Proteins
  • Minor Histocompatibility Antigens
  • Multiprotein Complexes
  • RNA, Small Interfering
  • Recombinant Fusion Proteins
  • Transcription Factors
  • enhancer-binding protein AP-3
  • Phosphotransferases (Alcohol Group Acceptor)
  • phosphatidylinositol phosphate 4-kinase