The actin binding protein adseverin regulates osteoclastogenesis.

Siavash Hassanpour,Yongqiang Wang,Michael Glogauer,Hongwei Jiang,Johannes W P Kuiper,Juha Tuukkanen

doi:10.1371/journal.pone.0109078

Siavash Hassanpour, Yongqiang Wang + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0109078

Copy DOI

Journal: PloS one	Publication Date: Oct 2, 2014
Citations: 74	License type: CC BY 4.0

Affiliation: University of Toronto, Sun Yat-sen University

Abstract

Adseverin (Ads), a member of the Gelsolin superfamily of actin binding proteins, regulates the actin cytoskeleton architecture by severing and capping existing filamentous actin (F-actin) strands and nucleating the assembly of new F-actin filaments. Ads has been implicated in cellular secretion, exocytosis and has also been shown to regulate chondrogenesis and megakaryoblastic leukemia cell differentiation. Here we report for the first time that Ads is involved in regulating osteoclastogenesis (OCG). Ads is induced during OCG downstream of RANK-ligand (RANKL) stimulation and is highly expressed in mature osteoclasts. The D5 isoform of Ads is not involved in regulating OCG, as its expression is not induced in response to RANKL. Three clonal Ads knockdown RAW264.7 (RAW) macrophage cell lines with varying degrees of Ads expression and OCG deficiency were generated. The most drastic OCG defect was noted in the clonal cell line with the greatest degree of Ads knockdown as indicated by a lack of TRAcP staining and multinucleation. RNAi mediated knockdown of Ads in osteoclast precursors resulted in distinct morphological changes characterized by altered F-actin distribution and increased filopodia formation. Ads knockdown precursor cells experienced enhanced migration while fusion of knockdown precursors cells was limited. Transient reintroduction of de novo Ads back into the knockdown system was capable of rescuing TRAcP expression but not osteoclast multinucleation most likely due to the transient nature of Ads expression. This preliminary study allows us to conclude that Ads is a RANKL induced early regulator of OCG with a potential role in pre-osteoclast differentiation and fusion.

Highlights

The bone extracellular matrix (ECM) has historically been described as a static and protective scaffold [1]
3.1 Adseverin expression is up-regulated during RANKLinduced OCG
An exploratory microarray was carried out to identify RANKL regulated genes during OCG. This microarray analysis identified eight cytoskeleton associated genes of interest with statistically significant changes in gene expression of least 2-fold in Bone marrow monocytes (BMMs) stimulated for two days with Macrophage Colony Stimulating Factor (M-CSF) and soluble RANKL (sRANKL) versus M-CSF alone (Fig. 1)

Summary

Introduction

The bone extracellular matrix (ECM) has historically been described as a static and protective scaffold [1]. Bone ECM is subjected to periodical remodeling to maintain its strength and integrity [2,3]. The task of skeletal remodeling falls in the domain of osteoclasts, which degrade the inorganic and organic phases of bone [1] and osteoblasts, which produce and secrete new matrix and regulate matrix mineralization [4]. Imbalances in bone remodeling result in perturbations of skeletal structure, integrity and function leading to diseases such as osteoporosis [5], osteopetrosis [6], inflammatory osteolysis such as rheumatic arthritis, periodontal disease [3,7] and Paget’s bone disease [3]. A thorough understanding of osteoclast formation or osteoclastogenesis (OCG) is crucial for development of novel drugs for treating bone-related diseases

Methods

Results

Conclusion