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STAC2 negatively regulates osteoclast formation by targeting the RANK signaling complex.

ABSTRACT: The receptor activator of nuclear factor-?B (RANK) protein activates various protein kinase signaling cascades, including those involving NF-?B, mitogen-activated protein kinase (MAPK), and Bruton tyrosine kinase (Btk)/tyrosine-protein kinase Tec. However, the mechanism underlying the negative regulation of RANK by downstream signaling molecules remains unclear. Here, we report that Src homology 3 domain and cysteine-rich domain-containing protein 2 (STAC2) is a novel RANK ligand-inducible protein that negatively regulates RANK-mediated osteoclast formation. STAC2 physically interacts with RANK and inhibits the formation of the RANK signaling complex, which contains Grb-2-associated binder 2 (Gab2) and phospholipase C?2 (PLC?2), thus leading to the suppression of RANK-mediated NF-?B and MAPK activation. Furthermore, STAC2 overexpression limits Btk/Tec-mediated PLC?2 phosphorylation via the interaction between STAC2 and Btk/Tec. Taken together, our results reveal a novel mechanism whereby RANK signaling is restricted by its physical interaction with STAC2.

SUBMITTER: Jeong E

PROVIDER: S-EPMC6113229 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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STAC2 negatively regulates osteoclast formation by targeting the RANK signaling complex.

Jeong Eutteum E Choi Han Kyoung HK Park Jin Hee JH Lee Soo Young SY

Cell death and differentiation 20180118 8

The receptor activator of nuclear factor-κB (RANK) protein activates various protein kinase signaling cascades, including those involving NF-κB, mitogen-activated protein kinase (MAPK), and Bruton tyrosine kinase (Btk)/tyrosine-protein kinase Tec. However, the mechanism underlying the negative regulation of RANK by downstream signaling molecules remains unclear. Here, we report that Src homology 3 domain and cysteine-rich domain-containing protein 2 (STAC2) is a novel RANK ligand-inducible prote ...[more]

PMID: 29348675

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Project description:Cells with monocyte/macrophage lineage expressing receptor activator of NF-?B (RANK) differentiate into osteoclasts following stimulation with the RANK ligand (RANKL). Cell adhesion signaling is also required for osteoclast differentiation from precursors. However, details of the mechanism by which cell adhesion signals induce osteoclast differentiation have not been fully elucidated. To investigate the participation of cell adhesion signaling in osteoclast differentiation, mouse bone marrow-derived macrophages (BMMs) were used as osteoclast precursors, and cultured on either plastic cell culture dishes (adherent condition) or the top surface of semisolid methylcellulose gel loaded in culture tubes (non-adherent condition). BMMs cultured under the adherent condition differentiated into osteoclasts in response to RANKL stimulation. However, under the non-adherent condition, the efficiency of osteoclast differentiation was markedly reduced even in the presence of RANKL. These BMMs retained macrophage characteristics including phagocytic function and gene expression profile. Lipopolysaccharide (LPS) and tumor necrosis factor -?TNF-? activated the NF-?B-mediated signaling pathways under both the adherent and non-adherent conditions, while RANKL activated the pathways only under the adherent condition. BMMs highly expressed RANK mRNA and protein under the adherent condition as compared to the non-adherent condition. Also, BMMs transferred from the adherent to non-adherent condition showed downregulated RANK expression within 24 hours. In contrast, transferring those from the non-adherent to adherent condition significantly increased the level of RANK expression. Moreover, interruption of cell adhesion signaling by echistatin, an RGD-containing disintegrin, decreased RANK expression in BMMs, while forced expression of either RANK or TNFR-associated factor 6 (TRAF6) in BMMs induced their differentiation into osteoclasts even under the non-adherent condition. These results suggest that cell adhesion signaling regulates RANK expression in osteoclast precursors.

Project description:RATIONALE:The highly conserved NOTCH (neurogenic locus notch homolog protein) signaling pathway functions as a key cell-cell interaction mechanism controlling cell fate and tissue patterning, whereas its dysregulation is implicated in a variety of developmental disorders and cancers. The pivotal role of endothelial NOTCH in regulation of angiogenesis is widely appreciated; however, little is known about what controls its signal transduction. Our previous study indicated the potential role of post-translational SUMO (small ubiquitin-like modifier) modification (SUMOylation) in vascular disorders. OBJECTIVE:The aim of this study was to investigate the role of SUMOylation in endothelial NOTCH signaling and angiogenesis. METHODS AND RESULTS:Endothelial SENP1 (sentrin-specific protease 1) deletion, in newly generated endothelial SENP1 (the major protease of the SUMO system)-deficient mice, significantly delayed retinal vascularization by maintaining prolonged NOTCH1 signaling, as confirmed in cultured endothelial cells. An in vitro SUMOylation assay and immunoprecipitation revealed that when SENP1 associated with N1ICD (NOTCH1 intracellular domain), it functions as a deSUMOylase of N1ICD SUMOylation on conserved lysines. Immunoblot and immunoprecipitation analyses and dual-luciferase assays of natural and SUMO-conjugated/nonconjugated NOTCH1 forms demonstrated that SUMO conjugation facilitated NOTCH1 cleavage. This released N1ICD from the membrane and stabilized it for translocation to the nucleus where it functions as a cotranscriptional factor. Functionally, SENP1-mediated NOTCH1 deSUMOylation was required for NOTCH signal activation in response to DLL4 (Delta-like 4) stimulation. This in turn suppressed VEGF (vascular endothelial growth factor) receptor signaling and angiogenesis, as evidenced by immunoblotted signaling molecules and in vitro angiogenesis assays. CONCLUSIONS:These results establish reversible NOTCH1 SUMOylation as a regulatory mechanism in coordinating endothelial angiogenic signaling; SENP1 acts as a critical intrinsic mediator of this process. These findings may apply to NOTCH-regulated biological events in nonvascular tissues and provide a novel therapeutic strategy for vascular diseases and tumors.

Dataset Information

STAC2 negatively regulates osteoclast formation by targeting the RANK signaling complex.

Publications

STAC2 negatively regulates osteoclast formation by targeting the RANK signaling complex.

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