Selective translational control of the Alzheimer amyloid precursor protein transcript by iron regulatory protein-1.
Iron influx increases the translation of the Alzheimer amyloid precursor protein (APP) via an iron-responsive element (IRE) RNA stem loop in its 5'-untranslated region. Equal modulated interaction of the iron regulatory proteins (IRP1 and IRP2) with canonical IREs controls iron-dependent translation of the ferritin subunits. However, our immunoprecipitation RT-PCR and RNA binding experiments demonstrated that IRP1, but not IRP2, selectively bound the APP IRE in human neural cells. This selective IRP1 interaction pattern was evident in human brain and blood tissue from normal and Alzheimer disease patients. We computer-predicted an optimal novel RNA stem loop structure for the human, rhesus monkey, and mouse APP IREs with reference to the canonical ferritin IREs but also the IREs encoded by erythroid heme biosynthetic aminolevulinate synthase and Hif-2α mRNAs, which preferentially bind IRP1. Selective 2'-hydroxyl acylation analyzed by primer extension analysis was consistent with a 13-base single-stranded terminal loop and a conserved GC-rich stem. Biotinylated RNA probes deleted of the conserved CAGA motif in the terminal loop did not bind to IRP1 relative to wild type probes and could no longer base pair to form a predicted AGA triloop. An AGU pseudo-triloop is key for IRP1 binding to the canonical ferritin IREs. RNA probes encoding the APP IRE stem loop exhibited the same high affinity binding to rhIRP1 as occurs for the H-ferritin IRE (35 pm). Intracellular iron chelation increased binding of IRP1 to the APP IRE, decreasing intracellular APP expression in SH-SY5Y cells. Functionally, shRNA knockdown of IRP1 caused increased expression of neural APP consistent with IRP1-APP IRE-driven translation.
Cho
Hyun-Hee
HH
Neurochemistry Laboratory, Department of Psychiatry-Neuroscience, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA.
Cahill
Catherine M
CM
Vanderburg
Charles R
CR
Scherzer
Clemens R
CR
Wang
Bin
B
Huang
Xudong
X
Rogers
Jack T
JT
D020121:5' Untranslated Regions; D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D006801:Humans; D007501:Iron / Q000378:metabolism; D035941:Iron Regulatory Protein 1 / Q000235:genetics / Q000378:metabolism*; D008253:Macaca mulatta; D051379:Mice; D009690:Nucleic Acid Conformation; D058255:Protease Nexins; D014176:Protein Biosynthesis; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*
D020121:5' Untranslated Regions; C545487:APP protein, human; D016564:Amyloid beta-Protein Precursor; D058255:Protease Nexins; D011956:Receptors, Cell Surface; D007501:Iron; C546175:ACO1 protein, human; D035941:Iron Regulatory Protein 1