Selective translational control of the Alzheimer amyloid precursor protein transcript by iron regulatory protein-1
Authors: Bin Wang
Xudong Huang
Clemens R Scherzer
Hyun-Hee Cho
Charles R Vanderburg
Jack T Rogers
Catherine M Cahill
Journal: Journal of Biological Chemistry (2010)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: Iron influx; Alzheimer amyloid precursor protein (APP); iron-responsive element (IRE); iron regulatory proteins (IRP1 and IRP2); RNA stem loop
Affiliations: Neurochemistry Laboratory, Department of Psychiatry-Neuroscience, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA.

Abstract:  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. 

Retracted: No

PubPeer comments:
 According to the caption fig 6a compares the specificity of IRP1 and IRP2 in binding to the 5u2032-UTR-specific APP IRE sequences concluding that IRP1 binds but not IRP2. However in the AD tissue, there are shadow boxes where one would expect to see IRP2. ![file] , 
 #1 To Lottia Cassis Many Thanks Lottia, Hyun Hee Cho performed this biotin-RNA Pull down experiment several times and could not see the IRP2 binding to the biotinylated APP IRE while it did interact with the ferritin counterpart. Your point is worth following up on, however, and we can soon indeed reprobe with several new IPR2 antibodies with new epitope specificities from our colleagues. Jack Jack Rogers , Ph.D. , 
 There are many undeclared slice sites in Fig 6A (red). The bands are from different images. ![file] , 
 #2 Could the authors please provide an update? ,