A novel cytoplasmic tail MXXXL motif mediates the internalization of prostate-specific membrane antigen

Mol Biol Cell. 2003 Dec;14(12):4835-45. doi: 10.1091/mbc.e02-11-0731. Epub 2003 Oct 3.


Prostate-specific membrane antigen (PSMA) is a transmembrane protein expressed at high levels in prostate cancer and in tumor-associated neovasculature. In this study, we report that PSMA is internalized via a clathrin-dependent endocytic mechanism and that internalization of PSMA is mediated by the five N-terminal amino acids (MWNLL) present in its cytoplasmic tail. Deletion of the cytoplasmic tail abolished PSMA internalization. Mutagenesis of N-terminal amino acid residues at position 2, 3, or 4 to alanine did not affect internalization of PSMA, whereas mutation of amino acid residues 1 or 5 to alanine strongly inhibited internalization. Using a chimeric protein composed of Tac antigen, the alpha-chain of interleukin 2-receptor, fused to the first five amino acids of PSMA (Tac-MWNLL), we found that this sequence is sufficient for PSMA internalization. In addition, inclusion of additional alanines into the MWNLL sequence either in the Tac chimera or the full-length PSMA strongly inhibited internalization. From these results, we suggest that a novel MXXXL motif in the cytoplasmic tail mediates PSMA internalization. We also show that dominant negative micro2 of the adaptor protein (AP)-2 complex strongly inhibits the internalization of PSMA, indicating that AP-2 is involved in the internalization of PSMA mediated by the MXXXL motif.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adaptor Protein Complex 2 / metabolism*
  • Amino Acid Motifs / physiology
  • Animals
  • Antigens, Surface / chemistry
  • Antigens, Surface / genetics
  • Antigens, Surface / metabolism*
  • COS Cells
  • Chlorocebus aethiops
  • Clathrin / metabolism*
  • Endocytosis / physiology*
  • Glutamate Carboxypeptidase II / chemistry
  • Glutamate Carboxypeptidase II / genetics
  • Glutamate Carboxypeptidase II / metabolism*
  • HeLa Cells
  • Humans
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • Models, Molecular
  • Mutation
  • Plasmids / genetics
  • Protein Binding
  • Receptors, Interleukin-2 / metabolism


  • Adaptor Protein Complex 2
  • Antigens, Surface
  • Clathrin
  • Receptors, Interleukin-2
  • FOLH1 protein, human
  • Glutamate Carboxypeptidase II