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CAP promoted osteoblast differentiation and vinexin inhibited calcification. Vinexin-or CAPdepleted (a,b,c,j,k) cells and vinexin α re-expressing cells (d,f,h) or CAP re-expressing cells seeded on plastic dishes were induced to differentiate into osteoblasts by incubating them with αMEM medium. (a,d,e) On day 6, RNAs were extracted and the expression of the ALP mRNA was quantified by qRT-PCR. The relative expression compared to control cells is shown from triplicate experiment. (b,c,f-i) On day 4, ALP activity was visualized and six images from each condition were obtained from two independent experiments. Representative images are shown. Scale bars: 400 μm. (c,h,i) Total intensity was quantified using ImageJ. (j,k) On day 6, cells were stained with Alizarin Red S and six images were obtained from two independent experiments. Representative images are shown. Scale bars: 200 μm. (k) The relative stained area was quantified using ImageJ. Values represent the mean ± s.e.m. Statistical significance was determined by one-way ANOVA with Tukey's test (a,c,k) and Student's t-test (d,e,h,i). ***p < 0.001 (by Tukey's test). § p < 0.01 (compared to mock using Student's t-test).
Source publication
The stiffness of extracellular matrix (ECM) directs the differentiation of mesenchymal stem cells (MSCs) through the transcriptional co-activators Yes-associated protein (YAP) and transcriptional coactivator with a PDZ-binding motif (TAZ). Although a recent study revealed the involvement of vinexin α and CAP (c-Cbl-associated proteins), two of vine...
Contexts in source publication
Context 1
... address whether cytoskeletal association of vinculin at FAs induced by CAP is involved in the regula- tion of MSC differentiation, vinculin T12, a semi-open and constitutively CSK-resistant vinculin mutant 12,16,39 , was introduced into CAP depleted cells and the adipocyte differentiation was examined (Fig. 4k,l). As shown in Fig. 4l, expression of GFP-T12 vinculin in CAP depleted cells suppressed the accumulation of lipid droplets to the levels comparable to control cells. In contrast, GFP-T12 suppressed the accumulation only slightly in control cells. These results suggest that CAP induces the cytoskeletal association of vinculin at FAs to suppress the adipocyte differentiation on rigid substrates. CAP promotes, but vinexin suppresses, differentiation into osteoblasts. We next investigated the effects of vinexin and CAP on osteoblast differentiation. Vinexin-or CAP-depleted cells were seeded onto rigid (plastic) substrates and differentiation into osteoblasts was induced. The mRNA expression of alka- line phosphatase (ALP), a marker for osteoblast differentiation, was down-regulated in CAP-depleted cells, whereas it was upregulated in vinexin-depleted cells (Fig. 5a). The osteoblastic phenotype was further analyzed using ALP-activity staining (Fig. 5b,c). Quantified data showed that CAP depletion significantly decreased the ALP-activity staining compared to control cells (Fig. 5c). On the other hand, vinexin depletion did not affect the staining. Re-expression of CAP rescued the decrease in ALP mRNA expression and activity stain- ing (Fig. 5e,g,i). Re-expression of vinexin α rescued the mRNA expression but, again, did not affect ALP activ- ity (Fig. 5d,f,h). The reason why vinexin depletion has different effects on ALP mRNA and activity staining is not clear. Post-transcriptional regulation could explain the difference, since ALP activity can be regulated post-transcriptionally 40 . Next, Alizarin Red S staining was performed to examine the effect on calcification. Vinexin depletion increased the staining compared to that in control cells (Fig. 5j,k), whereas CAP depletion slightly decreased the staining. Thus, these results suggest that CAP promotes differentiation into osteoblasts, whereas vinexin suppresses the ...
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... address whether cytoskeletal association of vinculin at FAs induced by CAP is involved in the regula- tion of MSC differentiation, vinculin T12, a semi-open and constitutively CSK-resistant vinculin mutant 12,16,39 , was introduced into CAP depleted cells and the adipocyte differentiation was examined (Fig. 4k,l). As shown in Fig. 4l, expression of GFP-T12 vinculin in CAP depleted cells suppressed the accumulation of lipid droplets to the levels comparable to control cells. In contrast, GFP-T12 suppressed the accumulation only slightly in control cells. These results suggest that CAP induces the cytoskeletal association of vinculin at FAs to suppress the adipocyte differentiation on rigid substrates. CAP promotes, but vinexin suppresses, differentiation into osteoblasts. We next investigated the effects of vinexin and CAP on osteoblast differentiation. Vinexin-or CAP-depleted cells were seeded onto rigid (plastic) substrates and differentiation into osteoblasts was induced. The mRNA expression of alka- line phosphatase (ALP), a marker for osteoblast differentiation, was down-regulated in CAP-depleted cells, whereas it was upregulated in vinexin-depleted cells (Fig. 5a). The osteoblastic phenotype was further analyzed using ALP-activity staining (Fig. 5b,c). Quantified data showed that CAP depletion significantly decreased the ALP-activity staining compared to control cells (Fig. 5c). On the other hand, vinexin depletion did not affect the staining. Re-expression of CAP rescued the decrease in ALP mRNA expression and activity stain- ing (Fig. 5e,g,i). Re-expression of vinexin α rescued the mRNA expression but, again, did not affect ALP activ- ity (Fig. 5d,f,h). The reason why vinexin depletion has different effects on ALP mRNA and activity staining is not clear. Post-transcriptional regulation could explain the difference, since ALP activity can be regulated post-transcriptionally 40 . Next, Alizarin Red S staining was performed to examine the effect on calcification. Vinexin depletion increased the staining compared to that in control cells (Fig. 5j,k), whereas CAP depletion slightly decreased the staining. Thus, these results suggest that CAP promotes differentiation into osteoblasts, whereas vinexin suppresses the ...
Context 3
... address whether cytoskeletal association of vinculin at FAs induced by CAP is involved in the regula- tion of MSC differentiation, vinculin T12, a semi-open and constitutively CSK-resistant vinculin mutant 12,16,39 , was introduced into CAP depleted cells and the adipocyte differentiation was examined (Fig. 4k,l). As shown in Fig. 4l, expression of GFP-T12 vinculin in CAP depleted cells suppressed the accumulation of lipid droplets to the levels comparable to control cells. In contrast, GFP-T12 suppressed the accumulation only slightly in control cells. These results suggest that CAP induces the cytoskeletal association of vinculin at FAs to suppress the adipocyte differentiation on rigid substrates. CAP promotes, but vinexin suppresses, differentiation into osteoblasts. We next investigated the effects of vinexin and CAP on osteoblast differentiation. Vinexin-or CAP-depleted cells were seeded onto rigid (plastic) substrates and differentiation into osteoblasts was induced. The mRNA expression of alka- line phosphatase (ALP), a marker for osteoblast differentiation, was down-regulated in CAP-depleted cells, whereas it was upregulated in vinexin-depleted cells (Fig. 5a). The osteoblastic phenotype was further analyzed using ALP-activity staining (Fig. 5b,c). Quantified data showed that CAP depletion significantly decreased the ALP-activity staining compared to control cells (Fig. 5c). On the other hand, vinexin depletion did not affect the staining. Re-expression of CAP rescued the decrease in ALP mRNA expression and activity stain- ing (Fig. 5e,g,i). Re-expression of vinexin α rescued the mRNA expression but, again, did not affect ALP activ- ity (Fig. 5d,f,h). The reason why vinexin depletion has different effects on ALP mRNA and activity staining is not clear. Post-transcriptional regulation could explain the difference, since ALP activity can be regulated post-transcriptionally 40 . Next, Alizarin Red S staining was performed to examine the effect on calcification. Vinexin depletion increased the staining compared to that in control cells (Fig. 5j,k), whereas CAP depletion slightly decreased the staining. Thus, these results suggest that CAP promotes differentiation into osteoblasts, whereas vinexin suppresses the ...
Context 4
... address whether cytoskeletal association of vinculin at FAs induced by CAP is involved in the regula- tion of MSC differentiation, vinculin T12, a semi-open and constitutively CSK-resistant vinculin mutant 12,16,39 , was introduced into CAP depleted cells and the adipocyte differentiation was examined (Fig. 4k,l). As shown in Fig. 4l, expression of GFP-T12 vinculin in CAP depleted cells suppressed the accumulation of lipid droplets to the levels comparable to control cells. In contrast, GFP-T12 suppressed the accumulation only slightly in control cells. These results suggest that CAP induces the cytoskeletal association of vinculin at FAs to suppress the adipocyte differentiation on rigid substrates. CAP promotes, but vinexin suppresses, differentiation into osteoblasts. We next investigated the effects of vinexin and CAP on osteoblast differentiation. Vinexin-or CAP-depleted cells were seeded onto rigid (plastic) substrates and differentiation into osteoblasts was induced. The mRNA expression of alka- line phosphatase (ALP), a marker for osteoblast differentiation, was down-regulated in CAP-depleted cells, whereas it was upregulated in vinexin-depleted cells (Fig. 5a). The osteoblastic phenotype was further analyzed using ALP-activity staining (Fig. 5b,c). Quantified data showed that CAP depletion significantly decreased the ALP-activity staining compared to control cells (Fig. 5c). On the other hand, vinexin depletion did not affect the staining. Re-expression of CAP rescued the decrease in ALP mRNA expression and activity stain- ing (Fig. 5e,g,i). Re-expression of vinexin α rescued the mRNA expression but, again, did not affect ALP activ- ity (Fig. 5d,f,h). The reason why vinexin depletion has different effects on ALP mRNA and activity staining is not clear. Post-transcriptional regulation could explain the difference, since ALP activity can be regulated post-transcriptionally 40 . Next, Alizarin Red S staining was performed to examine the effect on calcification. Vinexin depletion increased the staining compared to that in control cells (Fig. 5j,k), whereas CAP depletion slightly decreased the staining. Thus, these results suggest that CAP promotes differentiation into osteoblasts, whereas vinexin suppresses the ...
Context 5
... address whether cytoskeletal association of vinculin at FAs induced by CAP is involved in the regula- tion of MSC differentiation, vinculin T12, a semi-open and constitutively CSK-resistant vinculin mutant 12,16,39 , was introduced into CAP depleted cells and the adipocyte differentiation was examined (Fig. 4k,l). As shown in Fig. 4l, expression of GFP-T12 vinculin in CAP depleted cells suppressed the accumulation of lipid droplets to the levels comparable to control cells. In contrast, GFP-T12 suppressed the accumulation only slightly in control cells. These results suggest that CAP induces the cytoskeletal association of vinculin at FAs to suppress the adipocyte differentiation on rigid substrates. CAP promotes, but vinexin suppresses, differentiation into osteoblasts. We next investigated the effects of vinexin and CAP on osteoblast differentiation. Vinexin-or CAP-depleted cells were seeded onto rigid (plastic) substrates and differentiation into osteoblasts was induced. The mRNA expression of alka- line phosphatase (ALP), a marker for osteoblast differentiation, was down-regulated in CAP-depleted cells, whereas it was upregulated in vinexin-depleted cells (Fig. 5a). The osteoblastic phenotype was further analyzed using ALP-activity staining (Fig. 5b,c). Quantified data showed that CAP depletion significantly decreased the ALP-activity staining compared to control cells (Fig. 5c). On the other hand, vinexin depletion did not affect the staining. Re-expression of CAP rescued the decrease in ALP mRNA expression and activity stain- ing (Fig. 5e,g,i). Re-expression of vinexin α rescued the mRNA expression but, again, did not affect ALP activ- ity (Fig. 5d,f,h). The reason why vinexin depletion has different effects on ALP mRNA and activity staining is not clear. Post-transcriptional regulation could explain the difference, since ALP activity can be regulated post-transcriptionally 40 . Next, Alizarin Red S staining was performed to examine the effect on calcification. Vinexin depletion increased the staining compared to that in control cells (Fig. 5j,k), whereas CAP depletion slightly decreased the staining. Thus, these results suggest that CAP promotes differentiation into osteoblasts, whereas vinexin suppresses the ...
Context 6
... address whether cytoskeletal association of vinculin at FAs induced by CAP is involved in the regula- tion of MSC differentiation, vinculin T12, a semi-open and constitutively CSK-resistant vinculin mutant 12,16,39 , was introduced into CAP depleted cells and the adipocyte differentiation was examined (Fig. 4k,l). As shown in Fig. 4l, expression of GFP-T12 vinculin in CAP depleted cells suppressed the accumulation of lipid droplets to the levels comparable to control cells. In contrast, GFP-T12 suppressed the accumulation only slightly in control cells. These results suggest that CAP induces the cytoskeletal association of vinculin at FAs to suppress the adipocyte differentiation on rigid substrates. CAP promotes, but vinexin suppresses, differentiation into osteoblasts. We next investigated the effects of vinexin and CAP on osteoblast differentiation. Vinexin-or CAP-depleted cells were seeded onto rigid (plastic) substrates and differentiation into osteoblasts was induced. The mRNA expression of alka- line phosphatase (ALP), a marker for osteoblast differentiation, was down-regulated in CAP-depleted cells, whereas it was upregulated in vinexin-depleted cells (Fig. 5a). The osteoblastic phenotype was further analyzed using ALP-activity staining (Fig. 5b,c). Quantified data showed that CAP depletion significantly decreased the ALP-activity staining compared to control cells (Fig. 5c). On the other hand, vinexin depletion did not affect the staining. Re-expression of CAP rescued the decrease in ALP mRNA expression and activity stain- ing (Fig. 5e,g,i). Re-expression of vinexin α rescued the mRNA expression but, again, did not affect ALP activ- ity (Fig. 5d,f,h). The reason why vinexin depletion has different effects on ALP mRNA and activity staining is not clear. Post-transcriptional regulation could explain the difference, since ALP activity can be regulated post-transcriptionally 40 . Next, Alizarin Red S staining was performed to examine the effect on calcification. Vinexin depletion increased the staining compared to that in control cells (Fig. 5j,k), whereas CAP depletion slightly decreased the staining. Thus, these results suggest that CAP promotes differentiation into osteoblasts, whereas vinexin suppresses the ...
Citations
... Sorbs1 interactions with several structural and signaling cytoskeletal components, such as vinculin and paxillin, strengthened the idea that it might function as an adaptor protein coordinating multiple signaling complexes regulating the actin cytoskeleton [46,47]. In agreement with these observations, in vitro studies showed that Sorbs1 and the other family members are important regulators of actin-dependent processes, such as migration, adhesion, and mechano-transduction [45,48,49]. These cytoskeleton-based processes are essential to support and control the morphogenic events that endothelial cells have to go through during blood and lymphatic vessel formation [50]. ...
Background
Lymphangiogenesis, the formation of lymphatic vessels, is tightly linked to the development of the venous vasculature, both at the cellular and molecular levels. Here, we identify a novel role for Sorbs1, the founding member of the SoHo family of cytoskeleton adaptor proteins, in vascular and lymphatic development in the zebrafish.
Results
We show that Sorbs1 is required for secondary sprouting and emergence of several vascular structures specifically derived from the axial vein. Most notably, formation of the precursor parachordal lymphatic structures is affected in sorbs1 mutant embryos, severely impacting the establishment of the trunk lymphatic vessel network. Interestingly, we show that Sorbs1 interacts with the BMP pathway and could function outside of Vegfc signaling. Mechanistically, Sorbs1 controls FAK/Src signaling and subsequently impacts on the cytoskeleton processes regulated by Rac1 and RhoA GTPases. Inactivation of Sorbs1 altered cell-extracellular matrix (ECM) contacts rearrangement and cytoskeleton dynamics, leading to specific defects in endothelial cell migratory and adhesive properties.
Conclusions
Overall, using in vitro and in vivo assays, we identify Sorbs1 as an important regulator of venous and lymphatic angiogenesis independently of the Vegfc signaling axis. These results provide a better understanding of the complexity found within context-specific vascular and lymphatic development.
... A prior study showed that CAP protein encoded by the SORBS1 gene, combined with vinculin in the integrin complex and mediates homeostatic adaptation in response to external forces [90,91]. Numerous reports have confirmed that the knockdown of SORBS1 suppressed the osteogenic differentiation process of stem cells [92,93]. ...
Orthodontic tooth movement relies on bone remodeling and periodontal tissue regeneration in response to the complicated mechanical cues on the compressive and tensive side. In general, mechanical stimulus regulates the expression of mechano-sensitive coding and non-coding genes, which in turn affects how cells are involved in bone remodeling. Growing numbers of non-coding RNAs, particularly mechano-sensitive non-coding RNA, have been verified to be essential for the regulation of osteogenesis and osteoclastogenesis and have revealed how they interact with signaling molecules to do so. This review summarizes recent findings of non-coding RNAs, including microRNAs and long non-coding RNAs, as crucial regulators of gene expression responding to mechanical stimulation, and outlines their roles in bone deposition and resorption. We focused on multiple mechano-sensitive miRNAs such as miR-21, - 29, -34, -103, -494-3p, -1246, -138-5p, -503-5p, and -3198 that play a critical role in osteogenesis function and bone resorption. The emerging roles of force-dependent regulation of lncRNAs in bone remodeling are also discussed extensively. We summarized mechano-sensitive lncRNA XIST, H19, and MALAT1 along with other lncRNAs involved in osteogenesis and osteoclastogenesis. Ultimately, we look forward to the prospects of the novel application of non-coding RNAs as potential therapeutics for tooth movement and periodontal tissue regeneration.
... The sorbin homology (SoHo) family of adapter and scaffold proteins consists of three proteins: c-Cbl associated protein (CAP), also known as Sorbin and SH3 domain containing 1 (SORBS1), ArgBP2 (SORBS2), and Vinexin (SORBS3) (Ichikawa et al., 2017). Previous reports have suggested that SORBS1 encodes an insulin-signaling molecule mainly expressed in adipose and skeletal muscles, affects actin cytoskeleton organization, and modulates the location of focal adhesion complex, acting as a unique stiffness-mediated sensor for osteogenic differentiation (Hong et al., 2005;Engler et al., 2006;Wada et al., 2011;Kuroda et al., 2018). CAP protein encoded by the SORBS1 gene, combined with vinculin in the integrin complex, mediates homeostatic adaptation to external forces (Carisey and Ballestrem, 2011;Bharadwaj et al., 2013;Chen and Jacobs, 2013). ...
... CAP protein encoded by the SORBS1 gene, combined with vinculin in the integrin complex, mediates homeostatic adaptation to external forces (Carisey and Ballestrem, 2011;Bharadwaj et al., 2013;Chen and Jacobs, 2013). Reports from different groups have confirmed that SORBS1 knockdown inhibits the osteogenic differentiation process of stem cells (Holle et al., 2013(Holle et al., , 2016Kuroda et al., 2018). The present study used RNA sequences to profile gene and transcript expression associated with these RNAs during osteogenesis in BMSCs. ...
... Collectively, these results indicate that LOC100126784 and POM121L9P sponge miR-503-5p to modulate osteogenic differentiation at the early stages in induced BMSCs. SORBS1, also known as CAP, participates in MSC differentiation depending on the stiffness of the ECM (Lin et al., 2001a,b;Kuroda et al., 2018). MSCs link ECM with focal adhesions and activate internal biochemical signaling pathways related to the cytoskeleton (Watt and Huck, 2013). ...
Long non-coding RNAs (lncRNAs) play pivotal roles in mesenchymal stem cell differentiation. However, the mechanisms by which non-coding RNA (ncRNA) networks regulate osteogenic differentiation remain unclear. Therefore, our aim was to identify RNA-associated gene and transcript expression profiles during osteogenesis in bone marrow mesenchymal stem cells (BMSCs). Using transcriptome sequencing for differentially expressed ncRNAs and mRNAs between days 0 and 21 of osteogenic differentiation of BMSCs, we found that the microRNA (miRNA) miR-503-5p was significantly downregulated. However, the putative miR-503-5p target, sorbin and SH3 domain containing 1 (SORBS1), was significantly upregulated in osteogenesis. Moreover, through lncRNA-miRNA-mRNA interaction analyses and loss- and gain-of-function experiments, we discovered that the lncRNAs LOC100126784 and POM121L9P were abundant in the cytoplasm and enhanced BMSC osteogenesis by promoting SORBS1 expression. In contrast, miR-503-5p reversed this effect. Ago2 RNA-binding protein immunoprecipitation and dual-luciferase reporter assays further validated the direct binding of miR-503-5p to LOC100126784 and POM121L9P. Furthermore, SORBS1 knockdown suppressed early osteogenic differentiation in BMSCs, and co-transfection with SORBS1 small interfering RNAs counteracted the BMSCs’ osteogenic capacity promoted by LOC100126784- and POM121L9P-overexpressing lentivirus plasmids. Thus, the present study demonstrated that the lncRNAs LOC100126784 and POM121L9P facilitate the osteogenic differentiation of BMSCs via the miR-503-5p/SORBS1 axis, providing potential therapeutic targets for treating osteoporosis and bone defects.
... This result is consistent with the observed upregulated expression of Vinexin α and Cap in the BMSCs cultured on the SFH surface (Fig. 4k, l), which is related to the activation and unfolding of vinculin. 36,45 Silk fibroin and osteogenic cell behavior Y Long et al. ...
Silk fibroin (SF) can be used to construct various stiff material interfaces to support bone formation. An essential preparatory step is to partially transform SF molecules from random coils to β-sheets to render the material water insoluble. However, the influence of the SF conformation on osteogenic cell behavior at the material interface remains unknown. Herein, three stiff SF substrates were prepared by varying the β-sheet content (high, medium, and low). The substrates had a comparable chemical composition, surface topography, and wettability. When adsorbed fibronectin was used as a model cellular adhesive protein, the stability of the adsorbed protein-material interface, in terms of the surface stability of the SF substrates and the accompanying fibronectin detachment resistance, increased with the increasing β-sheet content of the SF substrates. Furthermore, (i) larger areas of cytoskeleton-associated focal adhesions, (ii) higher orders of cytoskeletal organization and (iii) more elongated cell spreading were observed for bone marrow-derived mesenchymal stromal cells (BMSCs) cultured on SF substrates with high vs. low β-sheet contents, along with enhanced nuclear translocation and activation of YAP/TAZ and RUNX2. Consequently, osteogenic differentiation of BMSCs was stimulated on high β-sheet substrates. These results indicated that the β-sheet content influences osteogenic differentiation of BMSCs on SF materials in vitro by modulating the stability of the adsorbed protein-material interface, which proceeds via protein-focal adhesion-cytoskeleton links and subsequent intracellular mechanotransduction. Our findings emphasize the role of the stability of the adsorbed protein-material interface in cellular mechanotransduction and the perception of stiff SF substrates with different β-sheet contents, which should not be overlooked when engineering stiff biomaterials.
... Force generation can be adjusted by controlling stress fiber dynamics or focal adhesion stability. One example of subfunctionalization is the differential use of SORBS family members to control the amount of force applied to the ECM (Kuroda et al., 2018). While the vertebrate paralogue SORBS2 interacts with α-actinin to regulate stress fiber contractility, the ancestral paralogue SORBS1 interacts with vinculin to control focal adhesion maturation (Ichikawa et al., 2017). ...
The emergence of collagen I in vertebrates resulted in a dramatic increase in the stiffness of the extracellular environment, supporting long-range force propagation and the development of low-compliant tissues necessary for the development of vertebrate traits including pressurized circulation and renal filtration. Vertebrates have also evolved integrins that can bind to collagens, resulting in the generation of higher tension and more efficient force transmission in the extracellular matrix. The stiffer environment provides an opportunity for the vertebrates to create new structures such as the stress fibers, new cell types such as endothelial cells, new developmental processes such as neural crest delamination, and new tissue organizations such as the blood-brain barrier. Molecular players found only in vertebrates allow the modification of conserved mechanisms as well as the design of novel strategies that can better serve the physiological needs of the vertebrates. These innovations collectively contribute to novel morphogenetic behaviors and unprecedented increases in the complexities of tissue mechanics and functions.
... The predictive power likely depends on the large size of the data sets, the combination of approaches at the discovery stage (correlation plus histology), and the fact that MYOCD is a constitutively nuclear transcription factor (62). Two of the four most MYOCD-responsive proteins examined, SLMAP and SORBS1, have been shown in recent studies to promote YAP/TAZ activation (4,31). Whether MYOCD promotes YAP/TAZ activity via these and/or other target predictions (SLMAP, SORBS1, SORBS2, PDLIM5, and PDLIM7) is an exciting avenue of future investigation. ...
Myocardin (MYOCD) is a critical regulator of smooth muscle cell (SMC) differentiation, but its transcriptional targets remain to be exhaustively characterized, especially at the protein level. Here we used a bioinformatics approach to identify novel potential MYOCD targets, and we confirm several at the protein level, including SORBS1, SLMAP, SYNM, and MCAM. We focused on SYNM, which encodes the intermediate filament protein synemin. SYNM rivalled smooth muscle myosin ( MYH11) for SMC specificity, and was controlled at the mRNA and protein levels by all myocardin-related transcription factors (MRTFs: MYOCD, MRTF-A/MKL1, and MRTF-B/MKL2). MRTF activity is regulated by the ratio of filamentous to globular actin, and SYNM was accordingly reduced by interventions that depolymerize actin, such as Latrunculin treatment and overexpression of constitutively active cofilin. Many MRTF target genes depend on SRF, but SYNM lacked SRF-binding motifs in its proximal promoter which was not directly regulated by MYOCD. Further, SYNM resisted SRF-silencing, and yet the time-course of induction closely paralleled that of the SRF-dependent target gene ACTA2. SYNM was repressed by the Ternary Complex Factor (TCF) FLI1, and was increased in mouse embryonic fibroblasts lacking three classical TCFs (ELK1, ELK3, and ELK4). Imaging showed co-localization of SYNM with the intermediate filament proteins desmin and vimentin, and MRTF-A/MKL1 increased SYNM-containing intermediate filaments in SMCs. These studies identify SYNM as a novel SRF-independent target of myocardin that is abundantly expressed in all SMCs.
... Additionally, MSC osteogenesis is dependent on substrate stiffness-induced adhesion reinforcement: on stiff matrices, vinculin depletion promotes the usually suppressed adipogenic differentiation [81]. This is linked to vinculin function in integrin-mediated adhesions, as knockdown of c-CBL-associated protein (CAP), a vinculin-binding protein that immobilizes vinculin in adhesions, is enough to recapitulate the phenotype [82]. ...
Somatic stem cells are characterized by their capacity for self-renewal and differentiation, making them integral for normal tissue homeostasis. Different stem cell functions are strongly affected by the specialized microenvironment surrounding the cells. Consisting of soluble signaling factors, extracellular matrix (ECM) ligands and other cells, but also biomechanical cues such as the viscoelasticity and topography of the ECM, these factors are collectively known as the niche. Cell-ECM interactions are mediated largely by integrins, a class of heterodimeric cell adhesion molecules. Integrins bind their ligands in the extracellular space and associate with the cytoskeleton inside the cell, forming a direct mechanical link between the cells and their surroundings. Indeed, recent findings have highlighted the importance of integrins in translating biophysical cues into changes in cell signaling and function, a multistep process known as mechanotransduction. The mechanical properties of the stem cell niche are important, yet the underlying molecular details of integrin-mediated mechanotransduction in stem cells, especially the roles of the different integrin heterodimers, remain elusive. Here, we introduce the reader to the concept of integrin-mediated mechanotransduction, summarize current knowledge on the role of integrin signaling and mechanotransduction in regulation of somatic stem cell functions, and discuss open questions in the field.
Cells within tissues are subject to various mechanical forces, including hydrostatic pressure, shear stress, compression, and tension. These mechanical stimuli can be converted into biochemical signals through mechanoreceptors or cytoskeleton-dependent response processes, shaping the microenvironment and maintaining cellular physiological balance. Several studies have demonstrated the roles of Yes-associated protein (YAP) and its homolog transcriptional coactivator with PDZ-binding motif (TAZ) as mechanotransducers, exerting dynamic influence on cellular phenotypes including differentiation and disease pathogenesis. This regulatory function entails the involvement of the cytoskeleton, nucleoskeleton, integrin, focal adhesions (FAs), and the integration of multiple signaling pathways, including extracellular signal-regulated kinase (ERK), wingless/ integrated (WNT), and Hippo signaling. Furthermore, emerging evidence substantiates the implication of long non-coding RNAs (lncRNAs) as mechanosensitive molecules in cellular mechanotransduction. In this review, we discuss the mechanisms through which YAP/TAZ and lncRNAs serve as effectors in responding to mechanical stimuli. Additionally, we summarize and elaborate on the crucial signal molecules involved in mechanotransduction.
Stem cells are regulated not only by biochemical signals but also by biophysical properties of extracellular matrix (ECM). The ECM is constantly monitored and remodeled because the fate of stem cells can be misdirected when the mechanical interaction between cells and ECM is imbalanced. A well‐defined ECM model for bone marrow‐derived human mesenchymal stem cells (hMSCs) based on supramolecular hydrogels containing reversible host–guest crosslinks is fabricated. The stiffness (Young's modulus E) of the hydrogels can be switched reversibly by altering the concentration of non‐cytotoxic, free guest molecules dissolved in the culture medium. Fine‐adjustment of substrate stiffness enables the authors to determine the critical stiffness level E* at which hMSCs turn the mechano‐sensory machinery on or off. Next, the substrate stiffness across E* is switched and the dynamic adaptation characteristics such as morphology, traction force, and YAP/TAZ signaling of hMSCs are monitored. These data demonstrate the instantaneous switching of traction force, which is followed by YAP/TAZ signaling and morphological adaptation. Periodical switching of the substrate stiffness across E* proves that frequent applications of mechanical stimuli drastically suppress hMSC proliferation. Mechanical stimulation across E* level using dynamic hydrogels is a promising strategy for the on‐demand control of hMSC transcription and proliferation.
Arginine kinase-binding protein 2 (ArgBP2) is an adapter protein that belongs to the sorbin homology (SoHo) family. The SoHo family also includes c-Cbl-associated protein (CAP) and vinexin, both of which share structural and functional similarities to ArgBP2. However, the role of SoHo family proteins in cell signaling, drug resistance, metabolism, and diseases, especially cancer, is not fully understood. Herein, we summarize the structure of SoHo family proteins, their post-translational modifications and the comprehensive network of cellular pathways regulated by these proteins, with an emphasis on ArgBP2. We also discuss the relevance of the SoHo family proteins in lipid raft distribution, extracellular matrix-associated microenvironments, and drug discovery. This review provides insights into the possibility of targeting ArgBP2 and other SoHo family proteins as drugs for use in preclinical trials.
