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Nuclear Export of Smads by RanBP3L Regulates Bone Morphogenetic Protein Signaling and Mesenchymal Stem Cell Differentiation.

ABSTRACT: Bone morphogenetic proteins (BMPs) play vital roles in regulating stem cell maintenance and differentiation. BMPs can induce osteogenesis and inhibit myogenesis of mesenchymal stem cells. Canonical BMP signaling is stringently controlled through reversible phosphorylation and nucleocytoplasmic shuttling of Smad1, Smad5, and Smad8 (Smad1/5/8). However, how the nuclear export of Smad1/5/8 is regulated remains unclear. Here we report that the Ran-binding protein RanBP3L acts as a nuclear export factor for Smad1/5/8. RanBP3L directly recognizes dephosphorylated Smad1/5/8 and mediates their nuclear export in a Ran-dependent manner. Increased expression of RanBP3L blocks BMP-induced osteogenesis of mouse bone marrow-derived mesenchymal stem cells and promotes myogenic induction of C2C12 mouse myoblasts, whereas depletion of RanBP3L expression enhances BMP-dependent stem cell differentiation activity and transcriptional responses. In conclusion, our results demonstrate that RanBP3L, as a nuclear exporter for BMP-specific Smads, plays a critical role in terminating BMP signaling and regulating mesenchymal stem cell differentiation.

SUBMITTER: Chen F

PROVIDER: S-EPMC4405638 | biostudies-literature | 2015 May

REPOSITORIES: biostudies-literature

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Nuclear Export of Smads by RanBP3L Regulates Bone Morphogenetic Protein Signaling and Mesenchymal Stem Cell Differentiation.

Chen Fenfang F Lin Xia X Xu Pinglong P Zhang Zhengmao Z Chen Yanzhen Y Wang Chao C Han Jiahuai J Zhao Bin B Xiao Mu M Feng Xin-Hua XH

Molecular and cellular biology 20150309 10

Bone morphogenetic proteins (BMPs) play vital roles in regulating stem cell maintenance and differentiation. BMPs can induce osteogenesis and inhibit myogenesis of mesenchymal stem cells. Canonical BMP signaling is stringently controlled through reversible phosphorylation and nucleocytoplasmic shuttling of Smad1, Smad5, and Smad8 (Smad1/5/8). However, how the nuclear export of Smad1/5/8 is regulated remains unclear. Here we report that the Ran-binding protein RanBP3L acts as a nuclear export fac ...[more]

PMID: 25755279

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Project description:Skeletal tissue regeneration following traumatic injury involves a complex cascade of growth factor signals that direct the differentiation of mesenchymal stem cells (MSCs) within the fracture. The necessity for controlled and localized expression of these factors has highlighted the role gene therapy may play as a promising treatment option for bone repair. However, the design of nanocarrier systems that negotiate efficient intracellular trafficking and nuclear delivery represents a significant challenge. Recent investigations have highlighted the roles histone tail sequences play in directing nuclear delivery and activating DNA transcription. We previously established the ability to recapitulate these natural histone tail activities within non-viral nanocarriers, improving gene transfer and expression by enabling effective navigation to the nucleus via retrograde vesicular trafficking. Herein, we demonstrate that histone-targeting leads to ∼4-fold enhancements in osteogenic bone morphogenetic protein-2 (BMP-2) expression by MSCs over 6 days, as compared with standard polymeric transfection reagents. This improved expression augmented chondrogenesis, an essential first step in fracture healing. Importantly, significant enhancements of cartilage-specific protein expression were triggered by histone-targeted gene transfer, as compared with the response to treatment with equivalent amounts of recombinant BMP-2 protein. In fact, an ∼100-fold increase in recombinant BMP-2 was required to achieve similar levels of chondrogenic gene and protein expression. The enhancements in differentiation achieved using histone-targeting were in part enabled by an increase in transcription factor expression, which functioned to drive MSC chondrogenesis. These novel findings demonstrate the utility of histone-targeted gene transfer strategies to enable substantial reductions in BMP-2 dosing for bone regenerative applications.Statement of significanceThis contribution addresses significant limitations in non-viral gene transfer for bone regenerative applications by exploiting a novel histone-targeting approach for cell-triggered delivery that induces osteogenic BMP-2 expression coincident with the initiation of bone repair. During repair, proliferating MSCs respond to a complex series of growth factor signals that direct their differentiation along cellular lineages essential to mature bone formation. Although these MSCs are ideal targets for enhanced transfection during cellular mitosis, few non-viral delivery approaches exist to enable maximization of this effect. Accordingly, this contribution seeks to utilize our histone-targeted nanocarrier design strategy to stimulate BMP-2 gene transfer in dividing MSCs. This gene-based approach leads to significantly augmented MSC chondrogenesis, an essential first step in bone tissue repair.

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Dataset Information

Nuclear Export of Smads by RanBP3L Regulates Bone Morphogenetic Protein Signaling and Mesenchymal Stem Cell Differentiation.

Publications

Nuclear Export of Smads by RanBP3L Regulates Bone Morphogenetic Protein Signaling and Mesenchymal Stem Cell Differentiation.

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