Communication of cAMP by connexin43 gap junctions regulates osteoblast signaling and gene expression

Gupta, Aditi; Anderson, Hidayah M.; Buo, Atum M.; Moorer, Megan C.; Ren, Margaret; Stains, Joseph P.

doi:10.1016/j.cellsig.2016.04.014

Cited by 39 publications

(40 citation statements)

References 66 publications

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“…Underscoring the importance of cell-cell diffusion of cAMP, interference with Cx43 using antisense oligonucleotides in osteoblastic cells reduces cAMP levels without affecting adenylate cyclase activity in response to PTH [66]. Notably, recent preliminary work suggests that Cx43 can amplify cAMP-dependent signaling and PKA-dependent gene transcription in osteoblasts in a cell-to-cell contact dependent manner [67]. As also noted, Cx43 can bind and sequester β-arrestin, thus preventing β-arrestin inhibition of cAMP signaling [60].…”

Section: Mechanisms Of Signal Modulation By Cx43 In Skeletal Cellsmentioning

confidence: 99%

Connexins in the skeleton

Stains

Civitelli

2016

Seminars in Cell & Developmental Biology

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Shaping of the skeleton (modeling) and its maintenance throughout life (remodeling) require coordinated activity among bone forming (osteoblasts) and resorbing cells (osteoclasts) and osteocytes (bone embedded cells). The gap junction protein connexin43 (Cx43) has emerged as a key modulator of skeletal growth and homeostasis. The skeletal developmental abnormalities present in oculodentodigital and craniometaphyseal dysplasias, both linked to Cx43 gene (GJA1) mutations, demonstrate that the skeleton is a major site of Cx43 action. Via direct action on osteolineage cells, including altering production of pro-osteoclastogenic factors, Cx43 contributes to peak bone mass acquisition, cortical modeling of long bones, and maintenance of bone quality. Cx43 also contributes in diverse ways to bone responsiveness to hormonal and mechanical signals. Skeletal biology research has revealed the complexity of Cx43 function; in addition to forming gap junctions and “hemichannels”, Cx43 provides a scaffold for signaling molecules. Hence, Cx43 actively participates in generation and modulation of cellular signals driving skeletal development and homeostasis. Pharmacological interference with Cx43 may in the future help remedy deterioration of bone quality occurring with aging, disuse and hormonal imbalances.

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Section: Mechanisms Of Signal Modulation By Cx43 In Skeletal Cellsmentioning

confidence: 99%

Connexins in the skeleton

Stains

Civitelli

2016

Seminars in Cell & Developmental Biology

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“…UMR106 cells were transiently transfected using the Jetprime transfection reagent (Polyplus, New York, NY), as described previously (Gupta et al, 2016). Endotoxin-free plasmid DNA was prepped using a Qiagen HI-Speed Maxi prep system, according to the manufacturer's specifications.…”

Section: Transient Transfections Co-immunoprecipitations and Westernmentioning

confidence: 99%

“…UMR106 cells were obtained from the ATCC and were cultured as described previously (Gupta et al, 2016). Primary BMSCs were prepared from the long bones of mice of the indicated genotype as described .…”

Section: Cell Culturementioning

confidence: 99%

Defective signaling, osteoblastogenesis and bone remodeling in a mouse model of connexin 43 C-terminal truncation

Moorer

Hebert

Tomlinson

et al. 2017

Journal of Cell Science

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In skeletal tissue, loss or mutation of the gap junction protein connexin 43 (Cx43, also known as GJA1) in cells of the osteoblast lineage leads to a profound cortical bone phenotype and defective tissue remodeling. There is mounting evidence in bone cells that the C-terminus (CT) of Cx43 is a docking platform for signaling effectors and is required for efficient downstream signaling. Here, we examined this function, using a mouse model of Cx43 CT-truncation (Gja1 K258Stop). Relative to Gja1 +/− controls, male Gja1 −/K258Stop mice have a cortical bone phenotype that is remarkably similar to those reported for deletion of the entire Cx43 gene in osteoblasts. Furthermore, we show that the Cx43 CT binds several signaling proteins that are required for optimal osteoblast function, including PKCδ, ERK1 and ERK2 (ERK1/2, also known as MAPK3 and MAPK1, respectively) and β-catenin. Deletion of the Cx43 CT domain affects these signaling cascades, impacting osteoblast proliferation, differentiation, and collagen processing and organization. These data imply that, at least in bone, Cx43 gap junctions not only exchange signals, but also recruit the appropriate effector molecules to the Cx43 CT in order to efficiently activate signaling cascades that affect cell function and bone acquisition.

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Section: Editorialmentioning

confidence: 99%

“…Finally, we showed that Cx43 increased the cAMP-dependent expression of RANKL in osteoblastic cells in culture, and enhanced the repression of Sost, implying a potential mechanism for the modulation of tissue remodelling. In total, these data demonstrate that Cx43 can communicate cAMP to impact signal transduction cascades and the expression of key bone effector molecules [8].In addition, our laboratory is interested in examining the role of gap junction protein Cx43 and its upregulation in cells of the joint during osteoarthritis (OA). We showed that increasing Cx43 levels in synovial cells is sufficient to enhance the expression of OA-associated catabolic and inflammatory genes.…”

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confidence: 99%

Connexin43 Gap Junctions Influences Osteoblast Signalling and Enhances Osteoarthritis Gene Expression

Gupta

2016

J Clin Exp Orthop

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EditorialIn multicellular organism, cells communicate with each other by gap junctions. The subunits of gap junction channels are proteins called connexins. Six-connexin proteins interact to form a ring-like pore structure called a hemichannel or connexon; these hemichannels dock to hemichannels on neighbouring cells, forming a gap junction's pore, which provides a direct intercellular passage for small molecules or ion to move between cells [1,2].Gap junction communication plays a critical role in bone cells such as osteoblast, osteocytes and osteoclast [3]. In humans, more than twenty connexins have been identified but Cx43, Cx45, Cx40, Cx46 and Cx37 are expressed in the bone. Most of the gap junction possesses four transmembrane regions, with cytoplasmic amino and carboxyl regions.Notably, Cx43, encoded by the Gja1 gene, is the most abundantly expressed connexin in bone, and has an important role in maintaining bone homeostasis [4]. Multiple evidences have suggested that gap junction communication is important for cell growth and differentiation. Mutations in Cx43 that lead to abnormally regulated cell-cell communication are associated with a number of diseases. One of them is oculodentodigital dysplasia (ODDD) and characterized by facial appearance include a pointed nose, undeveloped teeth and digital malformation or webbing between fourth and fifth fingers [5,6].Beyond the skeleton, Impaired Cx43 expression or loss of function has been implicated in several types of cancers. Cx43 mutations are also involved in sudden infant death syndrome (SIDS) in one year old or smaller babies, although the mechanism is still unexplained [7].Our lab is interested in the role of Cx43 in cells of the musculoskeletal system, including bone and cartilage. Recently, we investigated how cAMP second messenger communicated by bone cells via Cx43 where it can impact osteoblast function. We showed that overexpression of Cx43 in bone cells enhanced the activity of cAMP-response element driven transcriptional luciferase reporter (CRE-luc) and increased phospho-CREB and phospho-ERK1/2 expression by immunoblotting following treatment with prostaglandin E2 (PGE2) and forskolin. The Cx43-dependent potentiation of signalling following PGE2 treated cells was not accompanied by further increase in cAMP levels, suggesting that the cAMP was shared between the cells rather than Cx43 enhancing cAMP production. In support of this point, using a novel coculture assay in which one set of cells express a constitutively active Gs-alpha (donor cells) and a second set of cells express a cAMP-response element driven transcriptional reporter (acceptor cells), we showed that when both the Gs-alpha expressing donor cell and CRE-luc expressing acceptor cell express Cx43, then we could detect robust activation of the CRE-luc reporter the acceptor cell, indicating communication of the cAMP-dependent signal. This stimulation was not seen when the donor and acceptor cells were co-cultured in a transwell chamber where cell-to-cell contacts were not formed betwe...

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Communication of cAMP by connexin43 gap junctions regulates osteoblast signaling and gene expression

Cited by 39 publications

References 66 publications

Connexins in the skeleton

Connexins in the skeleton

Defective signaling, osteoblastogenesis and bone remodeling in a mouse model of connexin 43 C-terminal truncation

Connexin43 Gap Junctions Influences Osteoblast Signalling and Enhances Osteoarthritis Gene Expression

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