背景:多核是破骨细胞形成的标志,具有吸收骨基质的独特能力。在破骨细胞分化过程中,细胞骨架重组导致肌动蛋白带的产生和最终的骨吸收。四冬蛋白参与粘连,在各种细胞中的迁移和融合。然而,其在破骨细胞中的功能尚不清楚。在这项研究中,我们确定了Tm4sf19,一个四跨蛋白家族的成员,作为破骨细胞功能的调节剂。
方法:我们使用从野生型(WT)获得的骨髓来源的巨噬细胞研究Tm4sf19缺乏对破骨细胞分化的影响,Tm4sf19敲除(KO)和Tm4sf19(LELΔ)小鼠缺乏大胞外环(LEL)。我们分析了年轻和老年WT的骨量,KO和LELΔ小鼠通过μCT分析。研究了Tm4sf19LEL-Fc融合蛋白在破骨细胞分化和骨质疏松动物模型中的作用。
结果:我们发现Tm4sf19的缺乏抑制了破骨细胞的功能,而Tm4sf19的LEL是其在体外破骨细胞中的功能的原因。与WT小鼠相比,KO和LELΔ小鼠表现出较高的小梁骨量。我们发现Tm4sf19通过LEL与整合素αvβ3相互作用,并且这种结合通过调节整合素αvβ3下游的信号传导对破骨细胞中的细胞骨架重排很重要。用LEL-Fc融合蛋白处理在体外抑制破骨细胞功能,并且在体内施用LEL-Fc防止骨质疏松小鼠模型中的骨丢失。
结论:我们建议Tm4sf19调节破骨细胞功能,LEL-Fc可能是靶向由破骨细胞过度分化引起的骨破坏性疾病的有希望的药物。
BACKGROUND: Multinucleation is a hallmark of osteoclast formation and has a unique ability to resorb bone matrix. During osteoclast differentiation, the cytoskeleton reorganization results in the generation of actin belts and eventual bone resorption. Tetraspanins are involved in adhesion, migration and fusion in various cells. However, its function in osteoclast is still unclear. In this study, we identified
Tm4sf19, a member of the tetraspanin family, as a regulator of osteoclast function.
METHODS: We investigate the effect of
Tm4sf19 deficiency on osteoclast differentiation using bone marrow-derived macrophages obtained from wild type (WT),
Tm4sf19 knockout (KO) and
Tm4sf19 LELΔ mice lacking the large extracellular loop (LEL). We analyzed bone mass of young and aged WT, KO and LELΔ mice by μCT analysis. The effects of Tm4sf19 LEL-Fc fusion protein were accessed in osteoclast differentiation and osteoporosis animal model.
RESULTS: We found that deficiency of
Tm4sf19 inhibited osteoclast function and LEL of
Tm4sf19 was responsible for its function in osteoclasts in vitro. KO and LELΔ mice exhibited higher trabecular bone mass compared to WT mice. We found that Tm4sf19 interacts with integrin αvβ3 through LEL, and that this binding is important for cytoskeletal rearrangements in osteoclast by regulating signaling downstream of integrin αvβ3. Treatment with LEL-Fc fusion protein inhibited osteoclast function in vitro and administration of LEL-Fc prevented bone loss in an osteoporosis mouse model in vivo.
CONCLUSIONS: We suggest that
Tm4sf19 regulates osteoclast function and that LEL-Fc may be a promising drug to target bone destructive diseases caused by osteoclast hyper-differentiation.