In overactive human osteoclasts, we previously identified an alternative splicing event in LGALS8, encoding galectin-8, resulting in decreased expression of the long isoform. Galectin-8, which modulates cell-matrix interactions and functions intracellularly as a danger recognition receptor, has never been associated with osteoclast biology. In human osteoclasts, inhibition of galectin-8 expression revealed its roles in bone resorption, osteoclast nuclearity, and mTORC1 signaling regulation. Galectin-8 isoform-specific inhibition asserted a predominant role for the short isoform in bone resorption. Moreover, a liquid chromatography with tandem mass spectrometry (LC-MS/MS) proteomic analysis of galectin-8 isoforms performed in HEK293T cells identified 22 proteins shared by both isoforms. Meanwhile, nine interacting partners were specific for the short isoform, and none were unique to the long isoform. Interactors specific for the galectin-8 short isoform included cell adhesion proteins and lysosomal proteins. We confirmed the interactions of galectin-8 with CLCN3, CLCN7, LAMP1, and LAMP2, all known to localize to secretory vesicles, in human osteoclasts. Altogether, our study reveals direct roles of galectin-8 in osteoclast activity, mostly attributable to the short isoform.

中文翻译：

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Galectin-8 部分通过亚型特异性相互作用调节人破骨细胞活性。

在过度活跃的人类破骨细胞中，我们之前在编码半乳糖凝集素8的LGALS8中发现了一个选择性剪​​接事件，导致长亚型的表达减少。Galectin-8 可调节细胞-基质相互作用并在细胞内作为危险识别受体发挥作用，但从未与破骨细胞生物学相关。在人破骨细胞中，半乳糖凝集素 8 表达的抑制揭示了其在骨吸收、破骨细胞核​​和 mTORC1 信号调节中的作用。Galectin-8 异构体特异性抑制表明短异构体在骨吸收中起主导作用。此外，在 HEK293T 细胞中对半乳糖凝集素 8 异构体进行液相色谱串联质谱 (LC-MS/MS) 蛋白质组学分析，鉴定出两种异构体共有的 22 种蛋白质。同时，九个相互作用的伙伴是短异构体特有的，没有一个是长异构体所特有的。半乳糖凝集素 8 短亚型特异的相互作用物包括细胞粘附蛋白和溶酶体蛋白。我们证实了半乳糖凝集素 8 与 CLCN3、CLCN7、LAMP1 和 LAMP2 的相互作用，已知所有这些都定位于人类破骨细胞中的分泌囊泡。总而言之，我们的研究揭示了半乳糖凝集素 8 在破骨细胞活性中的直接作用，主要归因于短亚型。