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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-associated transcripts ARF6 and ARHGEF4 are translated in cell protrusions(A) Control-RNAi (Scr-1) S2-013 cells or IGF2BP3-RNAi (siIGF-1) S2-013 cells were incubated on fibronectin and stained with anti-ARF6 or anti-ARHGEF4 antibody (green). Actin filaments were labeled by phalloidin (red). Arrows, ARF and ARHGEF4 localized in cell protrusions. Blue, DAPI staining. Bars, 10 μm. (B) The myc-tagged IGF2BP3-rescue construct was transfected into IGF2BP3-RNAi S2-013 cells (siIGF-1). 48 h later, the cells were incubated on fibronectin. The cells were stained with antibodies against myc (green) and ARF6 (violet). Actin filaments were labeled by phalloidin (red). Arrows, ARF6 expression in cell protrusions. Blue, DAPI staining. Bars, 10 μm. (C) S2-013 cells treated as in (B) were stained with antibodies against myc (green) and ARHGEF4 (violet). Actin filaments were labeled by phalloidin (red). Arrows, ARHGEF4 expression in cell protrusions. Blue, DAPI staining. Bars, 10 μm.
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Figure 5: IGF2BP3-associated transcripts ARF6 and ARHGEF4 are translated in cell protrusions(A) Control-RNAi (Scr-1) S2-013 cells or IGF2BP3-RNAi (siIGF-1) S2-013 cells were incubated on fibronectin and stained with anti-ARF6 or anti-ARHGEF4 antibody (green). Actin filaments were labeled by phalloidin (red). Arrows, ARF and ARHGEF4 localized in cell protrusions. Blue, DAPI staining. Bars, 10 μm. (B) The myc-tagged IGF2BP3-rescue construct was transfected into IGF2BP3-RNAi S2-013 cells (siIGF-1). 48 h later, the cells were incubated on fibronectin. The cells were stained with antibodies against myc (green) and ARF6 (violet). Actin filaments were labeled by phalloidin (red). Arrows, ARF6 expression in cell protrusions. Blue, DAPI staining. Bars, 10 μm. (C) S2-013 cells treated as in (B) were stained with antibodies against myc (green) and ARHGEF4 (violet). Actin filaments were labeled by phalloidin (red). Arrows, ARHGEF4 expression in cell protrusions. Blue, DAPI staining. Bars, 10 μm.

Mentions: We hypothesized that IGF2BP3-bound mRNAs accumulated in cell protrusions may be locally translated in the protrusions. Specifically, we used control-RNAi S2-013 cells, IGF2BP3-RNAi S2-013 cells, and immunocytochemistry to determine whether IGF2BP3 had a role in ARF6 or ARHGEF4 protein localization. All cells were cultured on fibronectin. ARF6 and ARHGEF4 were expressed in the cytoplasm and membrane protrusions of control-RNAi cells; notably, immunofluorescent signals from ARF6 and ARHGEF4 in cell protrusions were weaker in IGF2BP3-RNAi cells than in control-RNAi cells; in fact, the ARF6 and ARHGEF4 signals in IGF2BP3-RNAi cells were restricted to cytoplasm of cell bodies (Figure 5A). Interestingly, peripheral actin structures seemed to be decreased in IGF2BP3-knockdown cells, compared to control cells (Figure 5A). Transfection of an IGF2BP3-rescue construct renewed expression of ARF6 (Figure 5B) and of ARHGEF4 (Figure 5C) in membrane protrusions of IGF2BP3-RNAi S2-013 cells. These findings indicated that IGF2BP3 was associated with translational regulation of the transcripts for ARF6 and ARHGEF4 in these 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-associated transcripts ARF6 and ARHGEF4 are translated in cell protrusions(A) Control-RNAi (Scr-1) S2-013 cells or IGF2BP3-RNAi (siIGF-1) S2-013 cells were incubated on fibronectin and stained with anti-ARF6 or anti-ARHGEF4 antibody (green). Actin filaments were labeled by phalloidin (red). Arrows, ARF and ARHGEF4 localized in cell protrusions. Blue, DAPI staining. Bars, 10 μm. (B) The myc-tagged IGF2BP3-rescue construct was transfected into IGF2BP3-RNAi S2-013 cells (siIGF-1). 48 h later, the cells were incubated on fibronectin. The cells were stained with antibodies against myc (green) and ARF6 (violet). Actin filaments were labeled by phalloidin (red). Arrows, ARF6 expression in cell protrusions. Blue, DAPI staining. Bars, 10 μm. (C) S2-013 cells treated as in (B) were stained with antibodies against myc (green) and ARHGEF4 (violet). Actin filaments were labeled by phalloidin (red). Arrows, ARHGEF4 expression in cell protrusions. Blue, DAPI staining. Bars, 10 μm.
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Figure 5: IGF2BP3-associated transcripts ARF6 and ARHGEF4 are translated in cell protrusions(A) Control-RNAi (Scr-1) S2-013 cells or IGF2BP3-RNAi (siIGF-1) S2-013 cells were incubated on fibronectin and stained with anti-ARF6 or anti-ARHGEF4 antibody (green). Actin filaments were labeled by phalloidin (red). Arrows, ARF and ARHGEF4 localized in cell protrusions. Blue, DAPI staining. Bars, 10 μm. (B) The myc-tagged IGF2BP3-rescue construct was transfected into IGF2BP3-RNAi S2-013 cells (siIGF-1). 48 h later, the cells were incubated on fibronectin. The cells were stained with antibodies against myc (green) and ARF6 (violet). Actin filaments were labeled by phalloidin (red). Arrows, ARF6 expression in cell protrusions. Blue, DAPI staining. Bars, 10 μm. (C) S2-013 cells treated as in (B) were stained with antibodies against myc (green) and ARHGEF4 (violet). Actin filaments were labeled by phalloidin (red). Arrows, ARHGEF4 expression in cell protrusions. Blue, DAPI staining. Bars, 10 μm.
Mentions: We hypothesized that IGF2BP3-bound mRNAs accumulated in cell protrusions may be locally translated in the protrusions. Specifically, we used control-RNAi S2-013 cells, IGF2BP3-RNAi S2-013 cells, and immunocytochemistry to determine whether IGF2BP3 had a role in ARF6 or ARHGEF4 protein localization. All cells were cultured on fibronectin. ARF6 and ARHGEF4 were expressed in the cytoplasm and membrane protrusions of control-RNAi cells; notably, immunofluorescent signals from ARF6 and ARHGEF4 in cell protrusions were weaker in IGF2BP3-RNAi cells than in control-RNAi cells; in fact, the ARF6 and ARHGEF4 signals in IGF2BP3-RNAi cells were restricted to cytoplasm of cell bodies (Figure 5A). Interestingly, peripheral actin structures seemed to be decreased in IGF2BP3-knockdown cells, compared to control cells (Figure 5A). Transfection of an IGF2BP3-rescue construct renewed expression of ARF6 (Figure 5B) and of ARHGEF4 (Figure 5C) in membrane protrusions of IGF2BP3-RNAi S2-013 cells. These findings indicated that IGF2BP3 was associated with translational regulation of the transcripts for ARF6 and ARHGEF4 in these 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