title: A cell-surface receptor for lipocalin 24p3 selectively mediates apoptosis and iron uptake.
abstract: The lipocalin mouse 24p3 has been implicated in diverse physiological processes, including apoptosis due to interleukin-3 (IL-3) deprivation and iron transport. Here we report cloning of the 24p3 cell-surface receptor (24p3R). Ectopic 24p3R expression confers on cells the ability to undergo either iron uptake or apoptosis, dependent upon the iron content of the ligand: Iron-loaded 24p3 increases intracellular iron concentration without promoting apoptosis; iron-lacking 24p3 decreases intracellular iron levels, which induces expression of the proapoptotic protein Bim, resulting in apoptosis. Intracellular iron delivery blocks Bim induction and suppresses apoptosis due to 24p3 addition or IL-3 deprivation. We find, unexpectedly, that the BCR-ABL oncoprotein activates expression of 24p3 and represses 24p3R expression, rendering BCR-ABL(+) cells refractory to secreted 24p3. By inhibiting BCR-ABL, imatinib induces 24p3R expression and, consequently, apoptosis. Our results reveal an unanticipated role for intracellular iron regulation in an apoptotic pathway relevant to BCR-ABL-induced myeloproliferative disease and its treatment.
authors.affiliation: Howard Hughes Medical Institute, Programs in Gene Function and Expression and Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA.
authors.forename: Laxminarayana R
authors.initials: LR
authors.lastname: Devireddy
authors.forename: Claude
authors.initials: C
authors.lastname: Gazin
authors.forename: Xiaochun
authors.initials: X
authors.lastname: Zhu
authors.forename: Michael R
authors.initials: MR
authors.lastname: Green
mesh_terms: D000209:Acute-Phase Proteins / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D006367:HeLa Cells; D006801:Humans; D007501:Iron / Q000378:metabolism*; D000071068:Lipocalin-2; D054834:Lipocalins; D051379:Mice; D008969:Molecular Sequence Data; D015513:Oncogene Proteins / Q000235:genetics* / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000378:metabolism*; D014162:Transfection
chemical_list: D000209:Acute-Phase Proteins; D007501:Iron; D000071068:Lipocalin-2; D054834:Lipocalins; D015513:Oncogene Proteins; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; C508313:Slc22a17 protein, mouse; C489506:LCN2 protein, human; C071332:Lcn2 protein, mouse