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Molecular Medicine (Cambridge, Mass.) Apr 2023The cytoskeletal architecture of osteoclasts (OCs) and bone resorption activity must be appropriately controlled for proper bone remodeling, which is associated with...
BACKGROUND
The cytoskeletal architecture of osteoclasts (OCs) and bone resorption activity must be appropriately controlled for proper bone remodeling, which is associated with osteoporosis. The RhoA protein of GTPase plays a regulatory role in cytoskeletal components and contributes to osteoclast adhesion, podosome positioning, and differentiation. Although osteoclast investigations have traditionally been performed by in vitro analysis, however, the results have been inconsistent, and the significance of RhoA in bone physiology and pathology is still unknown.
METHODS
We generated RhoA knockout mice by specifically deleting RhoA in the osteoclast lineage to understand more about RhoA's involvement in bone remodeling. The function of RhoA in osteoclast differentiation and bone resorption and the mechanisms were assessed using bone marrow macrophages (BMMs) in vitro. The ovariectomized (OVX) mouse model was adopted to examine the pathological effect of RhoA in bone loss.
RESULTS
Conditional deletion of RhoA in the osteoclast lineage causes a severe osteopetrosis phenotype, which is attributable to a bone resorption suppression. Further mechanistic studies suggest that RhoA deficiency suppresses Akt-mTOR-NFATc1 signaling during osteoclast differentiation. Additionally, RhoA activation is consistently related to the significant enhancement the osteoclast activity, which culminates in the development of an osteoporotic bone phenotype. Furthermore, in mice, the absence of RhoA in osteoclast precursors prevented occurring OVX-induced bone loss.
CONCLUSION
RhoA promoted osteoclast development via the Akt-mTOR-NFATc1 signaling pathway, resulting a osteoporosis phenotype, and that manipulating RhoA activity might be a therapeutic strategy for osteoporotic bone loss.
Topics: Animals; Mice; Bone Resorption; Cell Differentiation; NFATC Transcription Factors; Osteogenesis; Osteoporosis; Proto-Oncogene Proteins c-akt; rhoA GTP-Binding Protein; Signal Transduction; TOR Serine-Threonine Kinases
PubMed: 37020186
DOI: 10.1186/s10020-023-00638-1 -
Journal of Cell Science Dec 2019Podosomes are dynamic adhesion structures formed constitutively by macrophages, dendritic cells and osteoclasts and transiently in a wide variety of cells, such as... (Review)
Review
Podosomes are dynamic adhesion structures formed constitutively by macrophages, dendritic cells and osteoclasts and transiently in a wide variety of cells, such as endothelial cells and megakaryocytes. They mediate numerous functions, including cell-matrix adhesion, extracellular matrix degradation, mechanosensing and cell migration. Podosomes present as micron-sized F-actin cores surrounded by an adhesive ring of integrins and integrin-actin linkers, such as talin and vinculin. In this Review, we highlight recent research that has considerably advanced our understanding of the complex architecture-function relationship of podosomes by demonstrating that the podosome ring actually consists of discontinuous nano-clusters and that the actin network in between podosomes comprises two subsets of unbranched actin filaments, lateral and dorsal podosome-connecting filaments. These lateral and dorsal podosome-connecting filaments connect the core and ring of individual podosomes and adjacent podosomes, respectively. We also highlight recent insights into the podosome cap as a novel regulatory module of actomyosin-based contractility. We propose that these newly identified features are instrumental for the ability of podosomes to generate protrusion forces and to mechanically probe their environment. Furthermore, these new results point to an increasing complexity of podosome architecture and have led to our current view of podosomes as autonomous force generators that drive cell migration.
Topics: Animals; Cell Movement; Endothelial Cells; Humans; Megakaryocytes; Myosin Type II; Podosomes
PubMed: 31836688
DOI: 10.1242/jcs.236828 -
European Journal of Cell Biology Apr 2022Podosomes are highly dynamic actin-rich structures in a variety of cell types, especially monocytic cells. They fulfill multiple functions such as adhesion,... (Review)
Review
Podosomes are highly dynamic actin-rich structures in a variety of cell types, especially monocytic cells. They fulfill multiple functions such as adhesion, mechanosensing, or extracellular matrix degradation, thus allowing cells to detect and respond to a changing environment. These abilities are based on an intricate architecture that enables podosomes to sense mechanical properties of their substratum and to transduce them intracellularly in order to generate an appropriate cellular response. These processes are enabled through the tightly orchestrated interplay of more than 300 different components that are dynamically recruited during podosome formation and turnover. In this review, we discuss the different phases of the podosome life cycle and the current knowledge on regulatory factors that impact on the genesis, activity, dissolution and reemergence of podosomes. We also highlight mechanoregulatory processes that become important during these different stages, on the level of individual podosomes, and also at podosome sub- and superstructures.
Topics: Actins; Podosomes
PubMed: 35334303
DOI: 10.1016/j.ejcb.2022.151218 -
Journal of Cell Science May 2023Rac (herein referring to the Rac family) and Cdc42 are Rho GTPases that regulate the formation of lamellipoda and filopodia, and are therefore crucial in processes such...
Rac (herein referring to the Rac family) and Cdc42 are Rho GTPases that regulate the formation of lamellipoda and filopodia, and are therefore crucial in processes such as cell migration. Relocation-based biosensors for Rac and Cdc42 have not been characterized well in terms of their specificity or affinity. In this study, we identify relocation sensor candidates for both Rac and Cdc42. We compared their (1) ability to bind the constitutively active Rho GTPases, (2) specificity for Rac and Cdc42, and (3) relocation efficiency in cell-based assays. Subsequently, the relocation efficiency was improved by a multi-domain approach. For Rac1, we found a sensor candidate with low relocation efficiency. For Cdc42, we found several sensors with sufficient relocation efficiency and specificity. These optimized sensors enable the wider application of Rho GTPase relocation sensors, which was showcased by the detection of local endogenous Cdc42 activity at assembling invadopodia. Moreover, we tested several fluorescent proteins and HaloTag for their influence on the recruitment efficiency of the Rho location sensor, to find optimal conditions for a multiplexing experiment. This characterization and optimization of relocation sensors will broaden their application and acceptance.
Topics: rho GTP-Binding Proteins; Cell Movement; Podosomes; Pseudopodia
PubMed: 37226883
DOI: 10.1242/jcs.260802 -
Journal of Cellular Biochemistry Nov 2019Skeletal tissue homeostasis is maintained via the balance of osteoclastic bone resorption and osteoblastic bone formation. Autophagy and apoptosis are essential for the...
Skeletal tissue homeostasis is maintained via the balance of osteoclastic bone resorption and osteoblastic bone formation. Autophagy and apoptosis are essential for the maintenance of homeostasis and normal development in cells and tissues. We found that Bax-interacting factor 1 (Bif-1/Endophillin B1/SH3GLB1), involving in autophagy and apoptosis, was upregulated during osteoclastogenesis. Furthermore, mature osteoclasts expressed Bif-1 in the cytosol, particularly the perinuclear regions and podosome, suggesting that Bif-1 regulates osteoclastic bone resorption. Bif-1-deficient (Bif-1 ) mice showed increased trabecular bone volume and trabecular number. Histological analyses indicated that the osteoclast numbers increased in Bif-1 mice. Consistent with the in vivo results, osteoclastogenesis induced by receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL) was accelerated in Bif-1 mice without affecting RANKL-induced activation of RANK downstream signals, such as NF-κB and mitogen-activated protein kinases (MAPKs), CD115/RANK expression in osteoclast precursors, osteoclastic bone-resorbing activity and the survival rate. Unexpectedly, both the bone formation rate and osteoblast surface substantially increased in Bif-1 mice. Treatment with β-glycerophosphate (β-GP) and ascorbic acid (A.A) enhanced osteoblastic differentiation and mineralization in Bif-1 mice. Finally, bone marrow cells from Bif-1 mice showed a significantly higher colony-forming efficacy by the treatment with or without β-GP and A.A than cells from wild-type (WT) mice, suggesting that cells from Bif-1 mice had higher clonogenicity and self-renewal activity than those from WT mice. In summary, Bif-1 might regulate bone homeostasis by controlling the differentiation and function of both osteoclasts and osteoblasts (235 words).
Topics: Adaptor Proteins, Signal Transducing; Animals; Cancellous Bone; Homeostasis; Mice; Mice, Knockout; Osteoblasts; Osteoclasts; RANK Ligand; Receptor Activator of Nuclear Factor-kappa B
PubMed: 31243813
DOI: 10.1002/jcb.29193 -
Ageing Research Reviews Mar 2023With increasing age, bone tissue undergoes significant alterations in composition, architecture, and metabolic functions, probably causing senile osteoporosis.... (Review)
Review
With increasing age, bone tissue undergoes significant alterations in composition, architecture, and metabolic functions, probably causing senile osteoporosis. Osteoporosis possess the vast majority of bone disease and associates with a reduction in bone mass and increased fracture risk. Bone loss is on account of the disorder in osteoblast-induced bone formation and osteoclast-induced bone resorption. As a unique bone resorptive cell type, mature bone-resorbing osteoclasts exhibit dynamic actin-based cytoskeletal structures called podosomes that participate in cell-matrix adhesions specialized in the degradation of mineralized bone matrix. Podosomes share many of the same molecular constitutions as focal adhesions, but they have a unique structural organization, with a central core abundant in F-actin and encircled by scaffolding proteins, kinases and integrins. Here, we conclude recent advancements in our knowledge of the architecture and the functions of podosomes. We also discuss the regulatory pathways in osteoclast podosomes, providing a reference for future research on the podosomes of osteoclasts and considering podosomes as a therapeutic target for inhibiting bone resorption.
Topics: Humans; Actin Cytoskeleton; Actins; Bone Resorption; Osteoclasts; Podosomes
PubMed: 36621647
DOI: 10.1016/j.arr.2023.101842 -
Cancer Letters Feb 2024Growing evidence has suggested that increased matrix stiffness can significantly strengthen the malignant characteristics of hepatocellular carcinoma (HCC) cells....
Growing evidence has suggested that increased matrix stiffness can significantly strengthen the malignant characteristics of hepatocellular carcinoma (HCC) cells. However, whether and how increased matrix stiffness regulates the formation of invadopodia in HCC cells remain largely unknown. In the study, we developed different experimental systems in vitro and in vivo to explore the effects of matrix stiffness on the formation of invadopodia and its relevant molecular mechanism. Our results demonstrated that increased matrix stiffness remarkably augmented the migration and invasion abilities of HCC cells, upregulated the expressions of invadopodia-associated genes and enhanced the number of invadopodia. Two regulatory pathways contribute to matrix stiffness-driven invadopodia formation together in HCC cells, including direct triggering invadopodia formation through activating integrin β1 or Piezo1/ FAK/Src/Arg/cortactin pathway, and indirect stimulating invadopodia formation through improving EGF production to activate EGFR/Src/Arg/cortactin pathway. Src was identified as the common hub molecule of two synergistic regulatory pathways. Simultaneously, activation of integrin β1/RhoA/ROCK1/MLC2 and Piezo1/Ca/MLCK/MLC2 pathways mediate matrix stiffness-reinforced cell migration. This study uncovers a new mechanism by which mechanosensory pathway and biochemical signal pathway synergistically regulate the formation of invadopodia in HCC cells.
Topics: Humans; Carcinoma, Hepatocellular; Cortactin; Podosomes; Liver Neoplasms; Integrin beta1; Extracellular Matrix; Cell Line, Tumor; Neoplasm Invasiveness; rho-Associated Kinases
PubMed: 38145655
DOI: 10.1016/j.canlet.2023.216597 -
Journal of Cell Science Oct 2020Integrin adhesions are a structurally and functionally diverse family of transmembrane, multi-protein complexes that link the intracellular cytoskeleton to the... (Review)
Review
Integrin adhesions are a structurally and functionally diverse family of transmembrane, multi-protein complexes that link the intracellular cytoskeleton to the extracellular matrix (ECM). The different members of this family, including focal adhesions (FAs), focal complexes, fibrillar adhesions, podosomes and invadopodia, contain many shared scaffolding and signaling 'adhesome' components, as well as distinct molecules that perform specific functions, unique to each adhesion form. In this Hypothesis, we address the pivotal roles of mechanical forces, generated by local actin polymerization or actomyosin-based contractility, in the formation, maturation and functionality of two members of the integrin adhesions family, namely FAs and invadopodia, which display distinct structures and functional properties. FAs are robust and stable ECM contacts, associated with contractile stress fibers, while invadopodia are invasive adhesions that degrade the underlying matrix and penetrate into it. We discuss here the mechanisms, whereby these two types of adhesion utilize a similar molecular machinery to drive very different - often opposing cellular activities, and hypothesize that early stages of FAs and invadopodia assembly use similar biomechanical principles, whereas maturation of the two structures, and their 'adhesive' and 'invasive' functionalities require distinct sources of biomechanical reinforcement.
Topics: Cell Adhesion; Extracellular Matrix; Focal Adhesions; Integrins; Podosomes
PubMed: 33093229
DOI: 10.1242/jcs.244848 -
Journal of Cell Science Oct 2019Cell adhesion to the extracellular matrix is essential for cellular processes, such as migration and invasion. In response to cues from the microenvironment,... (Review)
Review
Cell adhesion to the extracellular matrix is essential for cellular processes, such as migration and invasion. In response to cues from the microenvironment, integrin-mediated adhesions alter cellular behaviour through cytoskeletal rearrangements. The tight association of the actin cytoskeleton with adhesive structures has been extensively studied, whereas the microtubule network in this context has gathered far less attention. In recent years, however, microtubules have emerged as key regulators of cell adhesion and migration through their participation in adhesion turnover and cellular signalling. In this Review, we focus on the interactions between microtubules and integrin-mediated adhesions, in particular, focal adhesions and podosomes. Starting with the association of microtubules with these adhesive structures, we describe the classical role of microtubules in vesicular trafficking, which is involved in the turnover of cell adhesions, before discussing how microtubules can also influence the actin-focal adhesion interplay through RhoGTPase signalling, thereby orchestrating a very crucial crosstalk between the cytoskeletal networks and adhesions.
Topics: Actin Cytoskeleton; Animals; Cytoskeleton; Focal Adhesions; Humans; Microtubules; Signal Transduction
PubMed: 31597743
DOI: 10.1242/jcs.232843 -
Cell Reports Oct 2023During metastasis, tumor cells invade through the basement membrane and intravasate into blood vessels and then extravasate into distant organs to establish metastases....
During metastasis, tumor cells invade through the basement membrane and intravasate into blood vessels and then extravasate into distant organs to establish metastases. Here, we report a critical role of a transmembrane serine protease fibroblast activation protein (FAP) in tumor metastasis. Expression of FAP and TWIST1, a metastasis driver, is significantly correlated in several types of human carcinomas, and FAP is required for TWIST1-induced breast cancer metastasis to the lung. Mechanistically, FAP is localized at invadopodia and required for invadopodia-mediated extracellular matrix degradation independent of its proteolytic activity. Live cell imaging shows that association of invadopodia precursors with FAP at the cell membrane promotes the stabilization and growth of invadopodia precursors into mature invadopodia. Together, our study identified FAP as a functional target of TWIST1 in driving tumor metastasis via promoting invadopodia-mediated matrix degradation and uncovered a proteolytic activity-independent role of FAP in stabilizing invadopodia precursors for maturation.
Topics: Humans; Female; Podosomes; Cell Line, Tumor; Peptide Hydrolases; Neoplasm Invasiveness; Breast Neoplasms; Membrane Proteins; Serine Endopeptidases; Fibroblasts; Extracellular Matrix; Melanoma, Cutaneous Malignant
PubMed: 37862167
DOI: 10.1016/j.celrep.2023.113302