GSK3 Inhibits Macropinocytosis and Lysosomal Activity through the Wnt Destruction Complex Machinery

Summary: Canonical Wnt signaling is emerging as a major regulator of endocytosis. Here, we report that Wnt-induced macropinocytosis is regulated through glycogen synthase kinase 3 (GSK3) and the β-catenin destruction complex. We find that mutation of Axin1, a tumor suppressor and component of the destruction complex, results in the activation of macropinocytosis. Surprisingly, inhibition of GSK3 by lithium chloride (LiCl), CHIR99021, or dominant-negative GSK3 triggers macropinocytosis. GSK3 inhibition causes a rapid increase in acidic endolysosomes that is independent of new protein synthesis. GSK3 inhibition or Axin1 mutation increases lysosomal activity, which can be followed with tracers of active cathepsin D, β-glucosidase, and ovalbumin degradation. Microinjection of LiCl into the blastula cavity of Xenopus embryos causes a striking increase in dextran macropinocytosis. The effects of GSK3 inhibition on protein degradation in endolysosomes are blocked by the macropinocytosis inhibitors EIPA or IPA-3, suggesting that increases in membrane trafficking drive lysosomal activity

Fibroblast Growth Factor 2 Regulates High Mobility Group A2 Expression in Human Bone Marrow‐Derived Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are an excellent source for numerous cellular therapies due to their simple isolation, low immunogenicity, multipotent differentiation potential and regenerative secretion profile. However, over-expanded MSCs show decreased therapeutic efficacy. This shortcoming may be circumvented by identifying methods that promote self-renewal of MSCs in culture. HMGA2 is a DNA-binding protein that regulates self-renewal in multiple types of stem cells through chromatin remodeling, but its impact on human bone marrow-derived MSCs is not known. Using an isolation method to obtain pure MSCs within 9 days in culture, we show that expression of HMGA2 quickly decreases during early expansion of MSCs, while let-7 microRNAs (which repress HMGA2) are simultaneously increased. Remarkably, we demonstrate that FGF-2, a growth factor commonly used to promote self-renewal in MSCs, rapidly induces HMGA2 expression in a time- and concentration-dependent manner. The signaling pathway involves FGF-2 receptor 1 (FGFR1) and ERK1/2, but acts independent from let-7. By silencing HMGA2 using shRNAs, we demonstrate that HMGA2 is necessary for MSC proliferation. However, we also show that over-expression of HMGA2 does not increase cell proliferation, but rather abrogates the mitogenic effect of FGF-2, possibly through inhibition of FGFR1. In addition, using different methods to assess in vitro differentiation, we show that modulation of HMGA2 inhibits adipogenesis, but does not affect osteogenesis of MSCs. Altogether, our results show that HMGA2 expression is associated with highly proliferating MSCs, is tightly regulated by FGF-2, and is involved in both proliferation and adipogenesis of MSCs. J. Cell. Biochem. 117: 2128-2137, 2016. © 2016 Wiley Periodicals, Inc

Fibroblast Growth Factor 2 Regulates High Mobility Group A2 Expression in Human Bone Marrow-Derived Mesenchymal Stem Cells.

Mesenchymal stem cells (MSCs) are an excellent source for numerous cellular therapies due to their simple isolation, low immunogenicity, multipotent differentiation potential and regenerative secretion profile. However, over-expanded MSCs show decreased therapeutic efficacy. This shortcoming may be circumvented by identifying methods that promote self-renewal of MSCs in culture. HMGA2 is a DNA-binding protein that regulates self-renewal in multiple types of stem cells through chromatin remodeling, but its impact on human bone marrow-derived MSCs is not known. Using an isolation method to obtain pure MSCs within 9 days in culture, we show that expression of HMGA2 quickly decreases during early expansion of MSCs, while let-7 microRNAs (which repress HMGA2) are simultaneously increased. Remarkably, we demonstrate that FGF-2, a growth factor commonly used to promote self-renewal in MSCs, rapidly induces HMGA2 expression in a time- and concentration-dependent manner. The signaling pathway involves FGF-2 receptor 1 (FGFR1) and ERK1/2, but acts independent from let-7. By silencing HMGA2 using shRNAs, we demonstrate that HMGA2 is necessary for MSC proliferation. However, we also show that over-expression of HMGA2 does not increase cell proliferation, but rather abrogates the mitogenic effect of FGF-2, possibly through inhibition of FGFR1. In addition, using different methods to assess in vitro differentiation, we show that modulation of HMGA2 inhibits adipogenesis, but does not affect osteogenesis of MSCs. Altogether, our results show that HMGA2 expression is associated with highly proliferating MSCs, is tightly regulated by FGF-2, and is involved in both proliferation and adipogenesis of MSCs. J. Cell. Biochem. 117: 2128-2137, 2016. © 2016 Wiley Periodicals, Inc

ZFP36-mediated mRNA decay regulates metabolism

Cellular metabolism is tightly regulated by growth factor signaling, which promotes metabolic rewiring to support growth and proliferation. While growth factor-induced transcriptional and post-translational modes of metabolic regulation have been well defined, whether post-transcriptional mechanisms impacting mRNA stability regulate this process is less clear. Here, we present the ZFP36/L1/L2 family of RNA-binding proteins and mRNA decay factors as key drivers of metabolic regulation downstream of acute growth factor signaling. We quantitatively catalog metabolic enzyme and nutrient transporter mRNAs directly bound by ZFP36 following growth factor stimulation-many of which encode rate-limiting steps in metabolic pathways. Further, we show that ZFP36 directly promotes the mRNA decay of Enolase 2 (Eno2), altering Eno2 protein expression and enzymatic activity, and provide evidence of a ZFP36/Eno2 axis during VEGF-stimulated developmental retinal angiogenesis. Thus, ZFP36-mediated mRNA decay serves as an important mode of metabolic regulation downstream of growth factor signaling within dynamic cell and tissue states

Endothelial Jagged1 levels and distribution are post-transcriptionally controlled by ZFP36 decay proteins

Summary: Vascular morphogenesis requires a delicate gradient of Notch signaling controlled, in part, by the distribution of ligands (Dll4 and Jagged1). How Jagged1 (JAG1) expression is compartmentalized in the vascular plexus remains unclear. Here, we show that Jag1 mRNA is a direct target of zinc-finger protein 36 (ZFP36), an RNA-binding protein involved in mRNA decay that we find robustly induced by vascular endothelial growth factor (VEGF). Endothelial cells lacking ZFP36 display high levels of JAG1 and increase angiogenic sprouting in vitro. Furthermore, mice lacking Zfp36 in endothelial cells display mispatterned and increased levels of JAG1 in the developing retinal vascular plexus. Abnormal levels of JAG1 at the sprouting front alters NOTCH1 signaling, increasing the number of tip cells, a phenotype that is rescued by imposing haploinsufficiency of Jag1. Our findings reveal an important feedforward loop whereby VEGF stimulates ZFP36, consequently suppressing Jag1 to enable adequate levels of Notch signaling during sprouting angiogenesis

Human and feline adipose-derived mesenchymal stem cells have comparable phenotype, immunomodulatory functions, and transcriptome.

BackgroundAdipose-derived mesenchymal stem cells (ASCs) are a promising cell therapy to treat inflammatory and immune-mediated diseases. Development of appropriate pre-clinical animal models is critical to determine safety and attain early efficacy data for the most promising therapeutic candidates. Naturally occurring diseases in cats already serve as valuable models to inform human clinical trials in oncologic, cardiovascular, and genetic diseases. The objective of this study was to complete a comprehensive side-by-side comparison of human and feline ASCs, with an emphasis on their immunomodulatory capacity and transcriptome.MethodsHuman and feline ASCs were evaluated for phenotype, immunomodulatory profile, and transcriptome. Additionally, transwells were used to determine the role of cell-cell contact in ASC-mediated inhibition of lymphocyte proliferation in both humans and cats.ResultsSimilar to human ASCs, feline ASCs were highly proliferative at low passages and fit the minimal criteria of multipotent stem cells including a compatible surface protein phenotype, osteogenic capacity, and normal karyotype. Like ASCs from all species, feline ASCs inhibited mitogen-activated lymphocyte proliferation in vitro, with or without direct ASC-lymphocyte contact. Feline ASCs mimic human ASCs in their mediator secretion pattern, including prostaglandin E2, indoleamine 2,3 dioxygenase, transforming growth factor beta, and interleukin-6, all augmented by interferon gamma secretion by lymphocytes. The transcriptome of three unactivated feline ASC lines were highly similar. Functional analysis of the most highly expressed genes highlighted processes including: 1) the regulation of apoptosis; 2) cell adhesion; 3) response to oxidative stress; and 4) regulation of cell differentiation. Finally, feline ASCs had a similar gene expression profile to noninduced human ASCs.ConclusionsFindings suggest that feline ASCs modulate lymphocyte proliferation using soluble mediators that mirror the human ASC secretion pattern. Uninduced feline ASCs have similar gene expression profiles to uninduced human ASCs, as revealed by transcriptome analysis. These data will help inform clinical trials using cats with naturally occurring diseases as surrogate models for human clinical trials in the regenerative medicine arena

Human and feline adipose-derived mesenchymal stem cells have comparable phenotype, immunomodulatory functions, and transcriptome.

BackgroundAdipose-derived mesenchymal stem cells (ASCs) are a promising cell therapy to treat inflammatory and immune-mediated diseases. Development of appropriate pre-clinical animal models is critical to determine safety and attain early efficacy data for the most promising therapeutic candidates. Naturally occurring diseases in cats already serve as valuable models to inform human clinical trials in oncologic, cardiovascular, and genetic diseases. The objective of this study was to complete a comprehensive side-by-side comparison of human and feline ASCs, with an emphasis on their immunomodulatory capacity and transcriptome.MethodsHuman and feline ASCs were evaluated for phenotype, immunomodulatory profile, and transcriptome. Additionally, transwells were used to determine the role of cell-cell contact in ASC-mediated inhibition of lymphocyte proliferation in both humans and cats.ResultsSimilar to human ASCs, feline ASCs were highly proliferative at low passages and fit the minimal criteria of multipotent stem cells including a compatible surface protein phenotype, osteogenic capacity, and normal karyotype. Like ASCs from all species, feline ASCs inhibited mitogen-activated lymphocyte proliferation in vitro, with or without direct ASC-lymphocyte contact. Feline ASCs mimic human ASCs in their mediator secretion pattern, including prostaglandin E2, indoleamine 2,3 dioxygenase, transforming growth factor beta, and interleukin-6, all augmented by interferon gamma secretion by lymphocytes. The transcriptome of three unactivated feline ASC lines were highly similar. Functional analysis of the most highly expressed genes highlighted processes including: 1) the regulation of apoptosis; 2) cell adhesion; 3) response to oxidative stress; and 4) regulation of cell differentiation. Finally, feline ASCs had a similar gene expression profile to noninduced human ASCs.ConclusionsFindings suggest that feline ASCs modulate lymphocyte proliferation using soluble mediators that mirror the human ASC secretion pattern. Uninduced feline ASCs have similar gene expression profiles to uninduced human ASCs, as revealed by transcriptome analysis. These data will help inform clinical trials using cats with naturally occurring diseases as surrogate models for human clinical trials in the regenerative medicine arena