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IGF2BP3-mediated translation in cell protrusions promotes cell invasiveness and metastasis of pancreatic cancer.

Taniuchi K, Furihata M, Hanazaki K, Saito M, Saibara T - Oncotarget (2014)

Bottom Line: Specific IGF2BP3-bound transcripts-ARF6 and ARHGEF4-that are preferentially translated in membrane protrusions induce further formation of membrane protrusions; consequently, IGF2BP3 promotes cell invasiveness and tumor metastasis.Our results provide insight into the link between regulation of localized translation in cell protrusions and the invasiveness and metastasis of pancreatic cancers.New therapies that prevent local translation in cell protrusions may hold significant clinical promise.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, Kochi Medical School, Kochi University, Nankoku, Kochi , Japan.

ABSTRACT
Pancreatic cancers are aggressive because they are highly invasive and highly metastatic; moreover, effective treatments for aggressive pancreatic cancers are lacking. Here, we report that IGF2BP3 promoted the invasiveness and metastasis of pancreatic cancers through locally translated IGF2BP3-bound transcripts. In neural cells, transcripts sorted into cytoplasmic RNA granules are transported to dendrites and translated in these dendrites, thereby mediating long-term synaptic plasticity; however, such cytoplasmic RNA granules are not known to contribute to the progression of pancreatic cancer. We show evidence that IGF2BP3 and IGF2BP3-bound transcripts are localized in cytoplasmic RNA granules that accumulate in membrane protrusions of pancreatic cancer cells. Specific IGF2BP3-bound transcripts-ARF6 and ARHGEF4-that are preferentially translated in membrane protrusions induce further formation of membrane protrusions; consequently, IGF2BP3 promotes cell invasiveness and tumor metastasis. Our results provide insight into the link between regulation of localized translation in cell protrusions and the invasiveness and metastasis of pancreatic cancers. New therapies that prevent local translation in cell protrusions may hold significant clinical promise.

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IGF2BP3 localizes in cytoplasmic SGs(A) S2-013 cells were incubated on fibronectin and stained with anti-IGF2BP3 (green) and anti-G3BP (red) antibodies. Actin filaments were labeled by phalloidin (violet). Arrows, IGF2BP3 colocalized with G3BP in cell protrusions. Blue, DAPI staining. Bar, 10 μm. (B) Immunoprecipitation of IGF2BP3 or G3BP from S2-013 cells cultured on fibronectin. Proteins in immunoprecipitates were examined on western blots probed with antibodies against IGF2BP3 and G3BP. Rabbit or mouse IgG isotype control antibody was used as an isotype control. (C) S2-013 cells were exposed to 500 μM SA for 30 min. Immunocytochemical staining with anti-IGF2BP3 antibody (green) and anti-G3BP or anti-TIA-1 (red) antibody are shown. Blue, DAPI staining. Bars, 10 μm.
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Figure 3: IGF2BP3 localizes in cytoplasmic SGs(A) S2-013 cells were incubated on fibronectin and stained with anti-IGF2BP3 (green) and anti-G3BP (red) antibodies. Actin filaments were labeled by phalloidin (violet). Arrows, IGF2BP3 colocalized with G3BP in cell protrusions. Blue, DAPI staining. Bar, 10 μm. (B) Immunoprecipitation of IGF2BP3 or G3BP from S2-013 cells cultured on fibronectin. Proteins in immunoprecipitates were examined on western blots probed with antibodies against IGF2BP3 and G3BP. Rabbit or mouse IgG isotype control antibody was used as an isotype control. (C) S2-013 cells were exposed to 500 μM SA for 30 min. Immunocytochemical staining with anti-IGF2BP3 antibody (green) and anti-G3BP or anti-TIA-1 (red) antibody are shown. Blue, DAPI staining. Bars, 10 μm.

Mentions: The intracellular CD24 that associates with RNA-binding proteins in cytoplasmic SGs interacts with an SG marker G3BP and immunoprecipitaes with IGF2BP3 in PDAC cells [9]. SGs contain some 40S subunit ribosomal proteins and several types of translation initiation factors, which together represent stalled translation preinitiation complexes; SGs also contain several types of RNA-binding proteins [17]. To investigate whether IGF2BP3-containing granules were SGs, S2-013 cells cultured on fibronectin were double-labeled with anti-IGF2BP3 and anti-G3BP [18] antibodies. We found that IGF2BP3 colocalized with G3BP in granules in membrane protrusions in which peripheral actin structures were increased (Figure 3A). Cytoplasmic IGF2BP3 that localized in the cytoplasm of the cell bodies did not colocalize with G3BP. Furthermore, extracts from S2-013 cells that had been grown on fibronectin were subjected to immunoprecipitation (IP) with anti-IGF2BP3 or anti-G3BP; notably, IGF2BP3 co-immunoprecipitated along with G3BP (Figure 3B). To verify that IGF2BP3 was present in SGs, S2-013 cells were subjected to sodium arsenite (SA)-induced oxidative stress and then double-labeled with anti-IGF2BP3 and anti-G3BP or anti-TIA-1. SGs form in the cytoplasm of S2-013 cells when SA is added to complete medium [9]. TIA-1 functions as a translation repressor, and like G3BP, it localizes to SGs [19]. When S2-013 cells were treated with SA, IGF2BP3 that localized in cytoplasmic granules colocalized with G3BP and with TIA-1, but cytoplasmic IGF2BP3 that did not localized in SGs did not colocalize with G3BP or TIA-1 (Figure 3C). These data indicated that IGF2BP3 localized in SGs may function to regulate levels of certain mRNAs in membrane protrusions.


IGF2BP3-mediated translation in cell protrusions promotes cell invasiveness and metastasis of pancreatic cancer.

Taniuchi K, Furihata M, Hanazaki K, Saito M, Saibara T - Oncotarget (2014)

IGF2BP3 localizes in cytoplasmic SGs(A) S2-013 cells were incubated on fibronectin and stained with anti-IGF2BP3 (green) and anti-G3BP (red) antibodies. Actin filaments were labeled by phalloidin (violet). Arrows, IGF2BP3 colocalized with G3BP in cell protrusions. Blue, DAPI staining. Bar, 10 μm. (B) Immunoprecipitation of IGF2BP3 or G3BP from S2-013 cells cultured on fibronectin. Proteins in immunoprecipitates were examined on western blots probed with antibodies against IGF2BP3 and G3BP. Rabbit or mouse IgG isotype control antibody was used as an isotype control. (C) S2-013 cells were exposed to 500 μM SA for 30 min. Immunocytochemical staining with anti-IGF2BP3 antibody (green) and anti-G3BP or anti-TIA-1 (red) antibody are shown. Blue, DAPI staining. Bars, 10 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Figure 3: IGF2BP3 localizes in cytoplasmic SGs(A) S2-013 cells were incubated on fibronectin and stained with anti-IGF2BP3 (green) and anti-G3BP (red) antibodies. Actin filaments were labeled by phalloidin (violet). Arrows, IGF2BP3 colocalized with G3BP in cell protrusions. Blue, DAPI staining. Bar, 10 μm. (B) Immunoprecipitation of IGF2BP3 or G3BP from S2-013 cells cultured on fibronectin. Proteins in immunoprecipitates were examined on western blots probed with antibodies against IGF2BP3 and G3BP. Rabbit or mouse IgG isotype control antibody was used as an isotype control. (C) S2-013 cells were exposed to 500 μM SA for 30 min. Immunocytochemical staining with anti-IGF2BP3 antibody (green) and anti-G3BP or anti-TIA-1 (red) antibody are shown. Blue, DAPI staining. Bars, 10 μm.
Mentions: The intracellular CD24 that associates with RNA-binding proteins in cytoplasmic SGs interacts with an SG marker G3BP and immunoprecipitaes with IGF2BP3 in PDAC cells [9]. SGs contain some 40S subunit ribosomal proteins and several types of translation initiation factors, which together represent stalled translation preinitiation complexes; SGs also contain several types of RNA-binding proteins [17]. To investigate whether IGF2BP3-containing granules were SGs, S2-013 cells cultured on fibronectin were double-labeled with anti-IGF2BP3 and anti-G3BP [18] antibodies. We found that IGF2BP3 colocalized with G3BP in granules in membrane protrusions in which peripheral actin structures were increased (Figure 3A). Cytoplasmic IGF2BP3 that localized in the cytoplasm of the cell bodies did not colocalize with G3BP. Furthermore, extracts from S2-013 cells that had been grown on fibronectin were subjected to immunoprecipitation (IP) with anti-IGF2BP3 or anti-G3BP; notably, IGF2BP3 co-immunoprecipitated along with G3BP (Figure 3B). To verify that IGF2BP3 was present in SGs, S2-013 cells were subjected to sodium arsenite (SA)-induced oxidative stress and then double-labeled with anti-IGF2BP3 and anti-G3BP or anti-TIA-1. SGs form in the cytoplasm of S2-013 cells when SA is added to complete medium [9]. TIA-1 functions as a translation repressor, and like G3BP, it localizes to SGs [19]. When S2-013 cells were treated with SA, IGF2BP3 that localized in cytoplasmic granules colocalized with G3BP and with TIA-1, but cytoplasmic IGF2BP3 that did not localized in SGs did not colocalize with G3BP or TIA-1 (Figure 3C). These data indicated that IGF2BP3 localized in SGs may function to regulate levels of certain mRNAs in membrane protrusions.

Bottom Line: Specific IGF2BP3-bound transcripts-ARF6 and ARHGEF4-that are preferentially translated in membrane protrusions induce further formation of membrane protrusions; consequently, IGF2BP3 promotes cell invasiveness and tumor metastasis.Our results provide insight into the link between regulation of localized translation in cell protrusions and the invasiveness and metastasis of pancreatic cancers.New therapies that prevent local translation in cell protrusions may hold significant clinical promise.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, Kochi Medical School, Kochi University, Nankoku, Kochi , Japan.

ABSTRACT
Pancreatic cancers are aggressive because they are highly invasive and highly metastatic; moreover, effective treatments for aggressive pancreatic cancers are lacking. Here, we report that IGF2BP3 promoted the invasiveness and metastasis of pancreatic cancers through locally translated IGF2BP3-bound transcripts. In neural cells, transcripts sorted into cytoplasmic RNA granules are transported to dendrites and translated in these dendrites, thereby mediating long-term synaptic plasticity; however, such cytoplasmic RNA granules are not known to contribute to the progression of pancreatic cancer. We show evidence that IGF2BP3 and IGF2BP3-bound transcripts are localized in cytoplasmic RNA granules that accumulate in membrane protrusions of pancreatic cancer cells. Specific IGF2BP3-bound transcripts-ARF6 and ARHGEF4-that are preferentially translated in membrane protrusions induce further formation of membrane protrusions; consequently, IGF2BP3 promotes cell invasiveness and tumor metastasis. Our results provide insight into the link between regulation of localized translation in cell protrusions and the invasiveness and metastasis of pancreatic cancers. New therapies that prevent local translation in cell protrusions may hold significant clinical promise.

Show MeSH
Related in: MedlinePlus