scholarly journals Nuclear export and mitochondrial and endoplasmic reticulum localization of IGF-binding protein 3 regulate its apoptotic properties

2010 ◽  
Vol 17 (2) ◽  
pp. 293-302 ◽  
Author(s):  
Vladislava Paharkova-Vatchkova ◽  
Kuk-Wha Lee
Keyword(s):  
Prostate Cancer ◽  
Endoplasmic Reticulum ◽  
Nuclear Export ◽  
Binding Protein ◽  
Subcellular Fractionation ◽  
Independent Manner ◽  
Fluorescence Confocal Microscopy ◽  
Igf Binding ◽  
Igf Binding Protein

Tumor suppression by IGF-binding protein 3 (IGFBP3) may occur in an IGF-independent manner, in addition to its role as a regulator of IGF bioavailability. After secretion, IGFBP3 is internalized, rapidly localized to the nucleus, and is later detected in the cytoplasm. We identified a putative nuclear export sequence (NES) in IGFBP3 between amino acids 217 and 228, analogous to the leucine-rich NES sequence of p53 and HIV Rev. Mutation of the NES prevents nucleocytoplasmic shuttling of IGFBP3 and blocks its ability to induce apoptosis. Targeting of IGFBP3 to the mitochondria and endoplasmic reticulum (ER) was confirmed by co-localization with organelle markers using fluorescence confocal microscopy and subcellular fractionation. Mitochondrial targeting was also demonstrated in vivo in IGFBP3-treated prostate cancer xenografts. These results show that IGFBP3 shuttles from the nucleus to the mitochondria and ER, and that nuclear export is essential for its effects on prostate cancer apoptosis.

scholarly journals The IGF system in neuroblastoma xenografts: focus on IGF-binding protein-6

2002 ◽  
Vol 172 (3) ◽  
pp. 467-476 ◽  
Author(s):  
P Grellier ◽  
D Berrebi ◽  
M Peuchmaur ◽  
S Babajko
Keyword(s):  
Binding Protein ◽  
Neuroblastoma Cell ◽  
Homogeneous Distribution ◽  
Tunel Staining ◽  
Human Neuroblastoma ◽  
Proteolytic Fragment ◽  
Igf Binding ◽  
Igf Binding Protein

With a view to investigating the implication of IGF-binding protein-6 (IGFBP-6) in the growth of neuroblastomas, nude mice were injected with IGFBP-6-expressing or control IGR-N-91 human neuroblastoma cells and the resulting xenografts examined. Expression of IGFBP-3, IGFBP-4 and type 1 and type 2 IGF receptor messengers was similar in control tumours and equal-sized IGFBP-6-expressing tumours that had developed. IGF-II was more strongly expressed in control tumours, and IGFBP-6-expressing tumours contained less IGFBP-2 than controls. In both populations, there was a significant positive correlation between IGF-II and IGFBP-2 expression. In small IGFBP-6-expressing xenografts where tumour development had apparently been arrested, haematoxylin--eosin and TUNEL staining revealed numerous apoptotic cells. In situ hybridization indicated homogeneous distribution of the IGFBP-6 signal in test tumours. In cell culture, IGFBP-6-expressing cells expressed similar amounts of IGFBP-2, IGF-II and N-myc mRNAs as control cells; but media conditioned by IGFBP-6-expressing cells contained less intact IGFBP-2 protein, with no increase in its proteolytic fragment. In media treated with plasminogen, in which IGFBP-2 was proteolysed, IGFBP-6 was increased. With its especially strong affinity for IGF-II and its resistance to proteolysis, IGFBP-6 would act by sequestering IGF-II, hence inhibiting its mitogenic and anti-apoptotic effects. In excess, IGFBP-6 would displace IGF-II from IGFBP-2 whose potentiation of IGF-II action would cease and whose susceptibility to degradation would be increased. This study therefore shows that IGFBP-6 plays a role in neuroblastoma cell growth in vivo and in vitro and that stable overexpression of IGFBP-6 leads to alteration of the initial balance between the IGFBPs.

scholarly journals Insulin-like growth factor (IgF)-I, IgF binding protein-3, and prostate cancer: correlation with gleason score

2015 ◽  
Vol 41 (1) ◽  
pp. 110-115 ◽  
Author(s):  
Lívia L. Corrêa ◽  
Leonardo Vieira Neto ◽  
Giovanna A. Balarini Lima ◽  
Rafael Gabrich ◽  
Luiz Carlos D. de Miranda ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Growth Factor ◽  
Gleason Score ◽  
Binding Protein ◽  
Insulin Like Growth Factor ◽  
Igf I ◽  
Igf Binding ◽  
Igf Binding Protein

scholarly journals The carboxy-terminal domain of IGF-binding protein-5 inhibits heparin binding to a site in the central domain

2001 ◽  
Vol 26 (3) ◽  
pp. 229-239 ◽  
Author(s):  
H Song ◽  
JH Shand ◽  
J Beattie ◽  
DJ Flint ◽  
GJ Allan
Keyword(s):  
Amino Acids ◽  
Binding Protein ◽  
Binding Activity ◽  
Heparin Binding ◽  
Central Domain ◽  
Basic Amino Acids ◽  
Terminal Domain ◽  
Igf Binding ◽  
Igf Binding Protein

The IGF-binding protein (IGFBP)-5 protein contains consensus heparin binding motifs in both its carboxy (C)-terminal and central domains, although only the C-terminal site has previously been shown to be functional. We have made two chimeric IGFBP proteins by switching domains between rat IGFBP-5 and -2, named BP552 and BP522 to reflect the domains present, and a truncated rat IGFBP-5 mutant (1-168), named BP550. The ability of these proteins and wild-type (wt) IGFBPs-5 and -2 to bind to either IGFs or heparin was determined using biosensor real-time analysis and heparin ligand blotting respectively. We report that the chimeric molecules have IGF binding affinities comparable to those of the native IGFBPs from which they were derived and, as expected, the binding of BP550 to IGFs was greatly compromised. More surprising was the finding that the ability of BP552 and BP550 to bind to heparin was equivalent to that of wtIGFBP-5, whereas wtIGFBP-2 and BP522 failed to bind. These results demonstrate that the active heparin binding site in BP552 and BP550 is contained within the central domain of IGFBP-5, and that this site is active only in the absence of the C-terminal domain. We subsequently mutated two basic amino acids (R136A:R137A) in the central consensus binding sites between residues 132-140. This resulted in the loss of heparin binding for BP550, confirming the importance of these two basic amino acids in the central domain heparin binding activity. In light of these findings, we suggest that C-terminally truncated fragments of IGFBP-5 generated in vivo by proteolysis could retain heparin/extracellular matrix binding properties.

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