Chondrocyte differentiation is crucial for cartilage formation. However, the complex processes and mechanisms coordinating chondrocyte proliferation and differentiation remain incompletely understood. Here, we report a novel function of the adaptor protein Gulp1 in chondrocyte differentiation. Gulp1 expression is upregulated during chondrogenic differentiation. Gulp1 knockdown in chondrogenic ATDC5 cells reduces the expression of chondrogenic and hypertrophic marker genes during differentiation. Furthermore, Gulp1 knockdown impairs cell growth arrest during chondrocyte differentiation and reduces the expression of the cyclin-dependent kinase inhibitor p21. The activation of the TGF-β/SMAD2/3 pathway, which is associated with p21 expression in chondrocytes, is impaired in Gulp1 knockdown cells. Collectively, these results demonstrate that Gulp1 contributes to cell growth arrest and chondrocyte differentiation by modulating the TGF-β/SMAD2/3 pathway.

中文翻译：

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Gulp1 通过 TGF-β/SMAD2/3 途径调节软骨细胞生长停滞和分化

软骨细胞分化对于软骨形成至关重要。然而，协调软骨细胞增殖和分化的复杂过程和机制仍未完全了解。在这里，我们报告了接头蛋白 Gulp1 在软骨细胞分化中的新功能。 Gulp1 表达在软骨分化过程中上调。软骨形成 ATDC5 细胞中 Gulp1 敲低会降低分化过程中软骨形成和肥大标记基因的表达。此外，Gulp1 敲低会损害软骨细胞分化过程中的细胞生长停滞，并减少细胞周期蛋白依赖性激酶抑制剂 p21 的表达。与软骨细胞中 p21 表达相关的 TGF-β/SMAD2/3 通路的激活在 Gulp1 敲除细胞中受损。总的来说，这些结果表明 Gulp1 通过调节 TGF-β/SMAD2/3 途径有助于细胞生长停滞和软骨细胞分化。