A novel conserved targeting motif found in ABCA transporters mediates trafficking to early post-Golgi compartments

J Lipid Res. 2011 Aug;52(8):1471-82. doi: 10.1194/jlr.M013284. Epub 2011 May 17.

Abstract

The ATP binding cassette, class A (ABCA) proteins are homologous polytopic transmembrane transporters that function as lipid pumps at distinct subcellular sites in a variety of cells. Located within the N terminus of these transporters, there exists a highly conserved xLxxKN motif of unknown function. To define its role, human ABCA3 was employed as a primary model representing ABCA transporters, while mouse ABCA1 was utilized to support major findings. Transfection studies showed colocalization of both transporters with surfactant protein C (SP-C), a marker peptide for successful protein targeting to lysosomal-like organelles. In contrast, alanine mutation of xLxxKN resulted in endoplasmic reticulum retention. As proof of principle, swapping xLxxKN for the known lysosomal targeting motif of SP-C resulted in post-Golgi targeting of the SP-C chimera. However, these products failed to reach their terminal processing compartments, suggesting that the xLxxKN motif only serves as a Golgi exit signal. We propose a model whereby an N-terminal signal sequence, xLxxKN, directs ABCA transporters to a post-Golgi vesicular sorting station where additional signals may be required for selective delivery of individual transporters to final subcellular destinations.

Publication types

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

MeSH terms

  • ATP Binding Cassette Transporter 1
  • ATP-Binding Cassette Transporters / chemistry
  • ATP-Binding Cassette Transporters / genetics
  • ATP-Binding Cassette Transporters / metabolism*
  • Amino Acid Motifs
  • Animals
  • Cell Line, Tumor
  • Endoplasmic Reticulum / metabolism*
  • Golgi Apparatus / metabolism*
  • Humans
  • Lysosomes / metabolism
  • Mice
  • Microscopy, Fluorescence
  • Molecular Sequence Data
  • Mutation
  • Plasmids
  • Protein Sorting Signals / physiology*
  • Protein Structure, Tertiary
  • Protein Transport
  • Pulmonary Surfactant-Associated Protein C / chemistry
  • Pulmonary Surfactant-Associated Protein C / genetics
  • Pulmonary Surfactant-Associated Protein C / metabolism*
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism*
  • Signal Transduction / physiology*
  • Transfection

Substances

  • ABCA1 protein, human
  • ABCA3 protein, human
  • ATP Binding Cassette Transporter 1
  • ATP-Binding Cassette Transporters
  • Protein Sorting Signals
  • Pulmonary Surfactant-Associated Protein C
  • Recombinant Fusion Proteins