%0 Journal Article
%T Iron-dependent degradation of IRP2 requires its C-terminal region and IRP structural integrity
%A Jian Wang
%A Guohua Chen
%A Julie Lee
%A Kostas Pantopoulos
%J BMC Molecular Biology
%D 2008
%I BioMed Central
%R 10.1186/1471-2199-9-15
%X To identify elements within IRP2 involved in the control of its stability, we undertook a systematic mutagenesis approach. Truncated versions of IRP2 were expressed in H1299 cells and analyzed for their response to iron. Deletion mutants lacking the entire C-terminal domain 4 (amino acids 719¨C963) of IRP2 remained stable following iron treatments. Moreover, the replacement of domain 4 of IRP1 with the corresponding region of IRP2 sensitized the chimerical IRP11¨C3/IRP24 protein to iron-dependent degradation, while the reverse manipulation gave rise to a stable chimerical IRP21¨C3/IRP14 protein. The deletion of just 26 or 34 C-terminal amino acids stabilized IRP2 against iron. However, the fusion of C-terminal IRP2 fragments to luciferase failed to sensitize the indicator protein for degradation in iron-loaded cells.Our data suggest that the C-terminus of IRP2 contains elements that are necessary but not sufficient for iron-dependent degradation. The functionality of these elements depends upon the overall IRP structure.Iron regulatory proteins, IRP1 and IRP2, post-transcriptionally control the expression of several mRNAs bearing iron responsive elements (IREs). In iron-deficient cells, IRE/IRP interactions account for the stabilization of transferrin receptor 1 (TfR1) mRNA and the translational inhibition of ferritin (H- and L-) mRNAs, resulting in increased uptake and reduced sequestration of iron [1]. IRPs regulate the expression of additional IRE-containing transcripts, such as those encoding erythroid aminolevulinate synthase (ALAS2), mitochondrial aconitase, the iron transporter ferroportin 1, myotonic dystrophy kinase-related Cdc42-binding kinase ¦Á (MRCK ¦Á), hypoxia inducible factor 2 ¦Á (HIF2¦Á), and splice variants of the divalent metal transporter DMT1 and the kinase Cdc14A [2-4]. Experiments with IRP1-/- and IRP2-/- cells and animals revealed that IRP2 exerts a dominant regulatory function in vivo [5].Both IRP1 and IRP2 share significant sequence similarity [1
%U http://www.biomedcentral.com/1471-2199/9/15