A novel cytoplasmic tail MXXXL motif mediates the internalization of prostate-specific membrane antigen.
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.
Rajasekaran
Sigrid A
SA
Department of Pathology and Laboratory Medicine, Molecular Biology Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90095, USA. arajasekaran@mednet.ucla.edu
Anilkumar
Gopalakrishnapillai
G
Oshima
Eri
E
Bowie
James U
JU
Liu
He
H
Heston
Warren
W
Bander
Neil H
NH
Rajasekaran
Ayyappan K
AK
D033962:Adaptor Protein Complex 2 / Q000378:metabolism*; D020816:Amino Acid Motifs / Q000502:physiology; D000818:Animals; D000954:Antigens, Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019556:COS Cells; D002522:Chlorocebus aethiops; D002966:Clathrin / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology*; D043425:Glutamate Carboxypeptidase II / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D011485:Protein Binding; D015375:Receptors, Interleukin-2 / Q000378:metabolism
D033962:Adaptor Protein Complex 2; D000954:Antigens, Surface; D002966:Clathrin; D015375:Receptors, Interleukin-2; C473848:FOLH1 protein, human; D043425:Glutamate Carboxypeptidase II