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SH3BP2 mutations potentiate osteoclastogenesis via PLC?.

ABSTRACT: To determine the mechanism for the increased osteoclastogenesis in the jaw of cherubism patients with SH3BP2 mutations we evaluated the effect of mutant compared to wild-type SH3BP2 on activation of osteoclast signaling pathways. Indeed mutant forms of SH3BP2 do induce greater osteoclastogenesis. Heterozygous activating mutations in exon 9 of SH3BP2 have been found in most patients with cherubism, an unusual genetic syndrome characterized by excessive remodeling of the mandible and maxilla due to spontaneous and excessive osteoclastic bone resorption. Here we have investigated the functional consequences of SH3BP2 mutations on sRANKL-induced osteoclastogenesis in RAW 264.7 pre-osteoclast cells. sRANKL-stimulated RAW 264.7 cells were transfected with wild-type or mutant SH3BP2 plasmids. NFAT-luciferase and tartrate resistant acid phosphatase (TRAP), a marker of osteoclastic differentiation, levels were evaluated. Western immunoblots were also performed to determine phosphorylation of key proteins involved in the PI-PLC pathway leading to NFATc1 translocation. Our results indicate that forced expression of mutant forms of SH3BP2, found in cherubism patients, in RAW 264.7 cells induce greater NFAT activity and greater expression of TRAP than forced expression of wild-type SH3BP2. These findings indicate that missense SH3BP2 mutations cause a gain of protein function. Moreover, over expression of SH3BP2 in RAW 264.7 cells potentiates sRANKL-stimulated phosphorylation of PLC?1 and PLC?2. Our studies demonstrate that cherubism is due to gain-of-function mutations in SH3BP2 that stimulate RANKL-induced activation of PLC?. The consequent activation of calcineurin and NFAT proteins induces the excessive osteoclastic phenotype of cherubism.

SUBMITTER: Lietman SA

PROVIDER: S-EPMC2948751 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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SH3BP2 mutations potentiate osteoclastogenesis via PLCγ.

Lietman Steven A SA Yin Lihong L Levine Michael A MA

Journal of orthopaedic research : official publication of the Orthopaedic Research Society 20101101 11

To determine the mechanism for the increased osteoclastogenesis in the jaw of cherubism patients with SH3BP2 mutations we evaluated the effect of mutant compared to wild-type SH3BP2 on activation of osteoclast signaling pathways. Indeed mutant forms of SH3BP2 do induce greater osteoclastogenesis. Heterozygous activating mutations in exon 9 of SH3BP2 have been found in most patients with cherubism, an unusual genetic syndrome characterized by excessive remodeling of the mandible and maxilla due t ...[more]

PMID: 20872577

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Project description:Cherubism (OMIM# 118400) is a genetic disorder with excessive jawbone resorption caused by mutations in SH3 domain binding protein 2 (SH3BP2), a signaling adaptor protein. Studies on the mouse model for cherubism carrying a P416R knock-in (KI) mutation have revealed that mutant SH3BP2 enhances tumor necrosis factor (TNF)-? production and receptor activator of nuclear factor-?B ligand (RANKL)-induced osteoclast differentiation in myeloid cells. TNF-? is expressed in human cherubism lesions, which contain a large number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells, and TNF-? plays a critical role in inflammatory bone destruction in homozygous cherubism mice (Sh3bp2(KI/KI) ). The data suggest a pathophysiological relationship between mutant SH3BP2 and TNF-?-mediated bone loss by osteoclasts. Therefore, we investigated whether P416R mutant SH3BP2 is involved in TNF-?-mediated osteoclast formation and bone loss. Here, we show that bone marrow-derived M-CSF-dependent macrophages (BMMs) from the heterozygous cherubism mutant (Sh3bp2(KI/+) ) mice are highly responsive to TNF-? and can differentiate into osteoclasts independently of RANKL in vitro by a mechanism that involves spleen tyrosine kinase (SYK) and phospholipase C?2 (PLC?2) phosphorylation, leading to increased nuclear translocation of NFATc1. The heterozygous cherubism mutation exacerbates bone loss with increased osteoclast formation in a mouse calvarial TNF-? injection model as well as in a human TNF-? transgenic mouse model (hTNFtg). SH3BP2 knockdown in RAW264.7 cells results in decreased TRAP-positive multinucleated cell formation. These findings suggest that the SH3BP2 cherubism mutation can cause jawbone destruction by promoting osteoclast formation in response to TNF-? expressed in cherubism lesions and that SH3BP2 is a key regulator for TNF-?-induced osteoclastogenesis. Inhibition of SH3BP2 expression in osteoclast progenitors could be a potential strategy for the treatment of bone loss in cherubism as well as in other inflammatory bone disorders.

Dataset Information

SH3BP2 mutations potentiate osteoclastogenesis via PLC?.

Publications

SH3BP2 mutations potentiate osteoclastogenesis via PLCγ.

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