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Chougule A, Zhang C, Vinokurov N, Mendez D, Vojtisek E, Shi C, Zhang J, Gardinier J. Purinergic signaling through the P2Y2 receptor regulates osteocytes' mechanosensitivity. J Cell Biol 2024; 223:e202403005. [PMID: 39212624 PMCID: PMC11363863 DOI: 10.1083/jcb.202403005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 06/20/2024] [Accepted: 08/07/2024] [Indexed: 09/04/2024] Open
Abstract
Osteocytes' response to dynamic loading plays a crucial role in regulating the bone mass but quickly becomes saturated such that downstream induction of bone formation plateaus. The underlying mechanisms that downregulate osteocytes' sensitivity and overall response to loading remain unknown. In other cell types, purinergic signaling through the P2Y2 receptor has the potential to downregulate the sensitivity to loading by modifying cell stiffness through actin polymerization and cytoskeleton organization. Herein, we examined the role of P2Y2 activation in regulating osteocytes' mechanotransduction using a P2Y2 knockout cell line alongside conditional knockout mice. Our findings demonstrate that the absence of P2Y2 expression in MLO-Y4 cells prevents actin polymerization while increasing the sensitivity to fluid flow-induced shear stress. Deleting osteocytes' P2Y2 expression in conditional-knockout mice enabled bone formation to increase when increasing the duration of exercise. Overall, P2Y2 activation under loading produces a negative feedback loop, limiting osteocytes' response to continuous loading by shifting the sensitivity to mechanical strain through actin stress fiber formation.
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Affiliation(s)
- Amit Chougule
- Bone and Joint Center, Henry Ford Health System, Detroit, MI, USA
- Henry Ford Health + Michigan State University Health Sciences, Detroit, MI, USA
- Department Physiology, College of Human Medicine, Michigan State University, East Lansing, MI, USA
| | - Chunbin Zhang
- Bone and Joint Center, Henry Ford Health System, Detroit, MI, USA
| | | | - Devin Mendez
- School of Medicine, Wayne State University, Detroit, MI, USA
| | | | - Chenjun Shi
- Department Biomedical Engineering, Wayne State University, Detroit, MI, USA
| | - Jitao Zhang
- Department Biomedical Engineering, Wayne State University, Detroit, MI, USA
| | - Joseph Gardinier
- Bone and Joint Center, Henry Ford Health System, Detroit, MI, USA
- Henry Ford Health + Michigan State University Health Sciences, Detroit, MI, USA
- Department Physiology, College of Human Medicine, Michigan State University, East Lansing, MI, USA
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Castle EL, Robinson CA, Douglas P, Rinker KD, Corcoran JA. Viral Manipulation of a Mechanoresponsive Signaling Axis Disassembles Processing Bodies. Mol Cell Biol 2021; 41:e0039921. [PMID: 34516278 PMCID: PMC8547432 DOI: 10.1128/mcb.00399-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 08/28/2021] [Accepted: 09/04/2021] [Indexed: 12/23/2022] Open
Abstract
Processing bodies (PBs) are ribonucleoprotein granules important for cytokine mRNA decay that are targeted for disassembly by many viruses. Kaposi's sarcoma-associated herpesvirus is the etiological agent of the inflammatory endothelial cancer, Kaposi's sarcoma, and a PB-regulating virus. The virus encodes kaposin B (KapB), which induces actin stress fibers (SFs) and cell spindling as well as PB disassembly. We now show that KapB-mediated PB disassembly requires actin rearrangements, RhoA effectors, and the mechanoresponsive transcription activator, YAP. Moreover, ectopic expression of active YAP or exposure of ECs to mechanical forces caused PB disassembly in the absence of KapB. We propose that the viral protein KapB activates a mechanoresponsive signaling axis and links changes in cell shape and cytoskeletal structures to enhanced inflammatory molecule expression using PB disassembly. Our work implies that cytoskeletal changes in other pathologies may similarly impact the inflammatory environment.
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Affiliation(s)
- Elizabeth L. Castle
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Carolyn-Ann Robinson
- Charbonneau Cancer Institute, University of Calgary, Calgary, Alberta, Canada
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
| | - Pauline Douglas
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
- Charbonneau Cancer Institute, University of Calgary, Calgary, Alberta, Canada
| | - Kristina D. Rinker
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
- Department of Chemical and Petroleum Engineering and Centre for Bioengineering Research and Education, University of Calgary, Calgary, Alberta, Canada
- Charbonneau Cancer Institute, University of Calgary, Calgary, Alberta, Canada
| | - Jennifer A. Corcoran
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
- Charbonneau Cancer Institute, University of Calgary, Calgary, Alberta, Canada
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
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Gardinier JD. The Diminishing Returns of Mechanical Loading and Potential Mechanisms that Desensitize Osteocytes. Curr Osteoporos Rep 2021; 19:436-443. [PMID: 34216359 PMCID: PMC9306018 DOI: 10.1007/s11914-021-00693-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/27/2021] [Indexed: 11/30/2022]
Abstract
Adaptation to mechanical loading is critical to maintaining bone mass and offers therapeutic potential to preventing age-related bone loss and osteoporosis. However, increasing the duration of loading is met with "diminishing returns" as the anabolic response quickly becomes saturated. As a result, the anabolic response to daily activities and repetitive bouts of loading is limited by the underlying mechanisms that desensitize and render bone unresponsive at the cellular level. Osteocytes are the primary cells that respond to skeletal loading and facilitate the overall anabolic response. Although many of osteocytes' signaling mechanisms activated in response to loading are considered anabolic in nature, several of them can also render osteocytes insensitive to further stimuli and thereby creating a negative feedback loop that limits osteocytes' overall response. The purpose of this review is to examine the potential mechanisms that may contribute to the loss of mechanosensitivity. In particular, we examined the inactivation/desensitization of ion channels and signaling molecules along with the potential role of endocytosis and cytoskeletal reorganization. The significance in defining the negative feedback loop is the potential to identify unique targets for enabling osteocytes to maintain their sensitivity. In doing so, we can begin to cultivate new strategies that capitalize on the anabolic nature of daily activities that repeatedly load the skeleton.
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Kwon S, Kim KS. Qualitative analysis of contribution of intracellular skeletal changes to cellular elasticity. Cell Mol Life Sci 2020; 77:1345-1355. [PMID: 31605149 PMCID: PMC11105102 DOI: 10.1007/s00018-019-03328-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 09/25/2019] [Accepted: 09/30/2019] [Indexed: 01/07/2023]
Abstract
Cells are dynamic structures that continually generate and sustain mechanical forces within their environments. Cells respond to mechanical forces by changing their shape, moving, and differentiating. These reactions are caused by intracellular skeletal changes, which induce changes in cellular mechanical properties such as stiffness, elasticity, viscoelasticity, and adhesiveness. Interdisciplinary research combining molecular biology with physics and mechanical engineering has been conducted to characterize cellular mechanical properties and understand the fundamental mechanisms of mechanotransduction. In this review, we focus on the role of cytoskeletal proteins in cellular mechanics. The specific role of each cytoskeletal protein, including actin, intermediate filaments, and microtubules, on cellular elasticity is summarized along with the effects of interactions between the fibers.
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Affiliation(s)
- Sangwoo Kwon
- Department of Biomedical Engineering, College of Medicine, Kyung Hee University, 1 Hoegi-dong, Dongdaemun-gu, Seoul, 02447, Republic of Korea
| | - Kyung Sook Kim
- Department of Biomedical Engineering, College of Medicine, Kyung Hee University, 1 Hoegi-dong, Dongdaemun-gu, Seoul, 02447, Republic of Korea.
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Wang W, Miller JP, Pannullo SC, Reinhart-King CA, Bordeleau F. Quantitative assessment of cell contractility using polarized light microscopy. JOURNAL OF BIOPHOTONICS 2018; 11:e201800008. [PMID: 29931742 PMCID: PMC6226342 DOI: 10.1002/jbio.201800008] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 06/20/2018] [Indexed: 06/01/2023]
Abstract
Cell contractility regulates multiple cell behaviors which contribute to both normal and pathological processes. However, measuring cell contractility remains a technical challenge in complex biological samples. The current state of the art technologies employed to measure cell contractility have inherent limitations that greatly limit the experimental conditions under which they can be used. Here, we use quantitative polarization microscopy to extract information about cell contractility. We show that the optical retardance signal measured from the cell body is proportional to cell contractility in 2-dimensional and 3-dimensional platforms, and as such can be used as a straightforward, tractable methodology to assess cell contractility in a variety of systems. This label-free optical method provides a novel and flexible way to assess cellular forces of single cells and monolayers in several cell types, fixed or live, in addition to cells present in situ in mouse tumor tissue samples. This easily implementable and experimentally versatile method will significantly contribute to the cell mechanics field.
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Affiliation(s)
- Wenjun Wang
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
| | - Joseph P. Miller
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY 14853
| | - Susan C. Pannullo
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY 14853
- Department of Neurological Surgery, Weill Cornell Medical College, New York, NY 10065
| | - Cynthia A. Reinhart-King
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY 14853
| | - Francois Bordeleau
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
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Thomas DG, Robinson DN. The fifth sense: Mechanosensory regulation of alpha-actinin-4 and its relevance for cancer metastasis. Semin Cell Dev Biol 2017; 71:68-74. [PMID: 28579451 DOI: 10.1016/j.semcdb.2017.05.024] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 05/26/2017] [Accepted: 05/30/2017] [Indexed: 12/18/2022]
Abstract
Metastatic cancer cells invading through dense tumor stroma experience internal and external forces that are sensed through a variety of mechanosensory proteins that drive adaptations for specific environments. Alpha-actinin-4 (ACTN4) is a member of the α-actinin family of actin crosslinking proteins that is upregulated in several types of cancers. It shares 86% protein similarity with α-actinin-1, another non-muscle ACTN isoform, which appears to have a more modest role, if any, in cancer progression. While they share regulatory mechanisms, such as phosphorylation, calcium binding, phosphatidyl inositol binding, and calpain cleavage, α-actinin-4 exhibits a unique mechanosensory regulation that α-actinin-1 does not. This behavior is mediated, at least in part, by each protein's actin-binding affinity as well as the catch-slip-bond behavior of the actin binding domains. We will discuss currently known modes of ACTN4 regulation, their interactions, and how mechanosensation may provide major therapeutic targeting potential for cancer metastasis.
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Affiliation(s)
- Dustin G Thomas
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD, 21205, USA.
| | - Douglas N Robinson
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD, 21205, USA; Department of Pharmacology and Molecular Science, Johns Hopkins University,Baltimore, MD, 21205, USA; Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD, 21205, USA; Department of Chemical and Biomolecular Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA.
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7
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Gardinier J, Yang W, Madden GR, Kronbergs A, Gangadharan V, Adams E, Czymmek K, Duncan RL. P2Y2 receptors regulate osteoblast mechanosensitivity during fluid flow. Am J Physiol Cell Physiol 2014; 306:C1058-67. [PMID: 24696143 DOI: 10.1152/ajpcell.00254.2013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mechanical stimulation of osteoblasts activates many cellular mechanisms including the release of ATP. Binding of ATP to purinergic receptors is key to load-induced osteogenesis. Osteoblasts also respond to fluid shear stress (FSS) with increased actin stress fiber formation (ASFF) that we postulate is in response to activation of the P2Y2 receptor (P2Y2R). Furthermore, we predict that ASFF increases cell stiffness and reduces the sensitivity to further mechanical stimulation. We found that small interfering RNA (siRNA) suppression of P2Y2R attenuated ASFF in response to FSS and ATP treatment. In addition, RhoA GTPase was activated within 15 min after the onset of FSS or ATP treatment and mediated ASFF following P2Y2R activation via the Rho kinase (ROCK)1/LIM kinase 2/cofilin pathway. We also observed that ASFF in response to FSS or ATP treatment increased the cell stiffness and was prevented by knocking down P2Y2R. Finally, we confirmed that the enhanced cell stiffness and ASFF in response to RhoA GTPase activation during FSS drastically reduced the mechanosensitivity of the osteoblasts based on the intracellular Ca(2+) concentration ([Ca(2+)]i) response to consecutive bouts of FSS. These data suggest that osteoblasts can regulate their mechanosensitivity to continued load through P2Y2R activation of the RhoA GTPase signaling cascade, leading to ASFF and increased cell stiffness.
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Affiliation(s)
- Joseph Gardinier
- Biomechanics and Movement Science, University of Delaware, Newark, Delaware
| | - Weidong Yang
- Department of Biological Sciences, University of Delaware, Newark, Delaware; and
| | - Gregory R Madden
- Department of Biological Sciences, University of Delaware, Newark, Delaware; and
| | - Andris Kronbergs
- Department of Biological Sciences, University of Delaware, Newark, Delaware; and
| | - Vimal Gangadharan
- Department of Biological Sciences, University of Delaware, Newark, Delaware; and
| | - Elizabeth Adams
- Bioimaging Center, Delaware Biotechnology Institute, Newark, Delaware
| | - Kirk Czymmek
- Department of Biological Sciences, University of Delaware, Newark, Delaware; and Bioimaging Center, Delaware Biotechnology Institute, Newark, Delaware
| | - Randall L Duncan
- Biomechanics and Movement Science, University of Delaware, Newark, Delaware; Department of Biological Sciences, University of Delaware, Newark, Delaware; and Bioimaging Center, Delaware Biotechnology Institute, Newark, Delaware
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Yang N, Schindeler A, McDonald MM, Seto JT, Houweling PJ, Lek M, Hogarth M, Morse AR, Raftery JM, Balasuriya D, MacArthur DG, Berman Y, Quinlan KGR, Eisman JA, Nguyen TV, Center JR, Prince RL, Wilson SG, Zhu K, Little DG, North KN. α-Actinin-3 deficiency is associated with reduced bone mass in human and mouse. Bone 2011; 49:790-8. [PMID: 21784188 DOI: 10.1016/j.bone.2011.07.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Revised: 06/28/2011] [Accepted: 07/07/2011] [Indexed: 10/18/2022]
Abstract
Bone mineral density (BMD) is a complex trait that is the single best predictor of the risk of osteoporotic fractures. Candidate gene and genome-wide association studies have identified genetic variations in approximately 30 genetic loci associated with BMD variation in humans. α-Actinin-3 (ACTN3) is highly expressed in fast skeletal muscle fibres. There is a common null-polymorphism R577X in human ACTN3 that results in complete deficiency of the α-actinin-3 protein in approximately 20% of Eurasians. Absence of α-actinin-3 does not cause any disease phenotypes in muscle because of compensation by α-actinin-2. However, α-actinin-3 deficiency has been shown to be detrimental to athletic sprint/power performance. In this report we reveal additional functions for α-actinin-3 in bone. α-Actinin-3 but not α-actinin-2 is expressed in osteoblasts. The Actn3(-/-) mouse displays significantly reduced bone mass, with reduced cortical bone volume (-14%) and trabecular number (-61%) seen by microCT. Dynamic histomorphometry indicated this was due to a reduction in bone formation. In a cohort of postmenopausal Australian women, ACTN3 577XX genotype was associated with lower BMD in an additive genetic model, with the R577X genotype contributing 1.1% of the variance in BMD. Microarray analysis of cultured osteoprogenitors from Actn3(-/-) mice showed alterations in expression of several genes regulating bone mass and osteoblast/osteoclast activity, including Enpp1, Opg and Wnt7b. Our studies suggest that ACTN3 likely contributes to the regulation of bone mass through alterations in bone turnover. Given the high frequency of R577X in the general population, the potential role of ACTN3 R577X as a factor influencing variations in BMD in elderly humans warrants further study.
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Affiliation(s)
- Nan Yang
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney 2145, NSW, Australia.
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