Ross Gracious R, Vodanovic-Jankovic Sanja, Benjamin Ivor J
Cardiovascular Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
J Cell Mol Med. 2024 Dec;28(24):e70273. doi: 10.1111/jcmm.70273.
Fibrosis, characterised by excessive extracellular matrix deposition, contributes to both organ failure and significant mortality worldwide. Whereas fibroblasts are activated into myofibroblasts, marked by phenotypic factors such as α-smooth muscle actin (α-SMA), periostin, fibroblast activation protein (FAP) and heat shock protein 47 (HSP47), the cellular processes of trans-differentiation for fibrosis development remain poorly understood. Herein, we hypothesised that the molecular signalling of geranylgeranyl pyrophosphate (GGPP), a crucial biochemical molecule for protein prenylation, is essential in the regulation of profibrotic mechanisms for fibroblast-to-myofibroblast activation. To test this hypothesis, we demonstrated pharmacological inhibition of geranylgeranyl pyrophosphate synthase (GGPS1) significantly decreased TGF-β1-dependent myofibroblast differentiation assessed by reduced α-SMA, periostin, FAP and HSP47 expression. Exogenous GGPP in the presence of GGPS1 inhibition restored TGF-β1-induced differentiation, supporting posttranslational requirements of GGPP modification during myofibroblast differentiation. Selective inhibition of either geranylgeranyl transferase or farnesyl transferase significantly impacted TGF-β1-induced myofibroblast α-SMA and HSP47 expression. The importance of protein prenylation as a key regulator of myofibroblast differentiation was remarkably revealed by an unexpected decrease in HSP47 expression. In contrast, direct HSP47 inhibition not only suppressed TGF-β1-induced α-SMA expression but surprisingly could not be rescued using exogenous GGPP. A selective role for the ER-resident chaperone HSP47 expression downstream of GGPP was suggested when the effects of GGPS1 inhibition on periostin expression were counteracted by GGPP and geranylgeranyl transferase inhibition. Taken together, our findings underscore for the first time the functional role of cholesterol synthesis-independent GGPP-dependent pathway in fibroblast-to-myofibroblast transition and open new potential therapeutic targets for antifibrosis therapies.
纤维化以细胞外基质过度沉积为特征，在全球范围内导致器官衰竭和高死亡率。成纤维细胞被激活成为肌成纤维细胞，其标志是α-平滑肌肌动蛋白（α-SMA）、骨膜蛋白、成纤维细胞激活蛋白（FAP）和热休克蛋白47（HSP47）等表型因子，但纤维化发展过程中细胞转分化的具体机制仍知之甚少。在此，我们假设香叶基香叶基焦磷酸（GGPP）作为蛋白质异戊二烯化的关键生化分子，其分子信号在调节成纤维细胞向肌成纤维细胞激活的促纤维化机制中至关重要。为验证这一假设，我们发现对香叶基香叶基焦磷酸合酶（GGPS1）的药理学抑制显著降低了TGF-β1依赖的肌成纤维细胞分化，表现为α-SMA、骨膜蛋白、FAP和HSP47表达减少。在抑制GGPS1的情况下，外源性GGPP可恢复TGF-β1诱导的分化，这支持了肌成纤维细胞分化过程中GGPP修饰的翻译后需求。选择性抑制香叶基香叶基转移酶或法尼基转移酶会显著影响TGF-β1诱导的肌成纤维细胞α-SMA和HSP47表达。HSP47表达意外下降显著揭示了蛋白质异戊二烯化作为肌成纤维细胞分化关键调节因子的重要性。相比之下，直接抑制HSP47不仅抑制了TGF-β1诱导的α-SMA表达，而且令人惊讶的是，外源性GGPP无法挽救这种抑制作用。当GGPP和香叶基香叶基转移酶抑制抵消了GGPS1抑制对骨膜蛋白表达的影响时，提示了内质网驻留伴侣蛋白HSP47在GGPP下游表达的选择性作用。综上所述，我们的研究首次强调了不依赖胆固醇合成的GGPP依赖途径在成纤维细胞向肌成纤维细胞转变中的功能作用，并为抗纤维化治疗开辟了新的潜在治疗靶点。
