Myofibroblasts are key contributors to pathological fibrotic conditions of several major organs. The transdifferentiation of fibroblasts into myofibroblasts requires both a mechanical signal and transforming growth factor-β (TGF-β) signaling. The cation channel transient receptor potential vanilloid 4 (TRPV4) is a critical mediator of myofibroblast transdifferentiation and in vivo fibrosis through its mechanosensitivity to extracellular matrix stiffness. Here, we showed that TRPV4 promoted the transdifferentiation of human and mouse lung fibroblasts through its interaction with phosphoinositide 3-kinase γ (PI3Kγ), forming nanomolar-affinity, intracellular TRPV4-PI3Kγ complexes. TGF-β induced the recruitment of TRPV4-PI3Kγ complexes to the plasma membrane and increased the activities of both TRPV4 and PI3Kγ. Using gain- and loss-of-function approaches, we showed that both TRPV4 and PI3Kγ were required for myofibroblast transdifferentiation as assessed by the increased production of α-smooth muscle actin and its incorporation into stress fibers, cytoskeletal changes, collagen-1 production, and contractile force. Expression of various mutant forms of the PI3Kγ catalytic subunit (p110γ) in cells lacking PI3Kγ revealed that only the noncatalytic, amino-terminal domain of p110γ was necessary and sufficient for TGF-β-induced TRPV4 plasma membrane recruitment and myofibroblast transdifferentiation. These data suggest that TGF-β stimulates a noncanonical scaffolding action of PI3Kγ, which recruits TRPV4-PI3Kγ complexes to the plasma membrane, thereby increasing myofibroblast transdifferentiation. Given that both TRPV4 and PI3Kγ have pleiotropic actions, targeting the interaction between them could provide a specific therapeutic approach for inhibiting myofibroblast transdifferentiation.

中文翻译：

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TRPV4-PI3Kγ复合物向质膜的移位驱动了成肌纤维细胞的转分化。

肌成纤维细胞是几种主要器官的病理性纤维化状况的关键因素。成纤维细胞向肌成纤维细胞的转分化既需要机械信号，又需要转化生长因子-β（TGF-β）信号。阳离子通道瞬态受体电位香草酸4（TRPV4）通过对细胞外基质硬度的机械敏感性，是成肌纤维细胞转分化和体内纤维化的关键介质。在这里，我们显示TRPV4通过与磷酸肌醇3-激酶γ（PI3Kγ）相互作用促进了人和小鼠肺成纤维细胞的转分化，形成了纳摩尔亲和力的细胞内TRPV4-PI3Kγ复合物。TGF-β诱导TRPV4-PI3Kγ复合物募集到质膜，并增加TRPV4和PI3Kγ的活性。使用功能获得和丧失功能的方法，我们发现成肌纤维细胞转分化同时需要TRPV4和PI3Kγ，这可以通过α平滑肌肌动蛋白产量的增加及其掺入应激纤维，细胞骨架的变化，胶原1的产生，和收缩力。在缺乏PI3Kγ的细胞中表达各种突变形式的PI3Kγ催化亚基（p110γ）表明，只有p110γ的非催化氨基末端结构域对于TGF-β诱导的TRPV4质膜募集和成纤维细胞转分化是必需的和充分的。这些数据表明，TGF-β刺激了PI3Kγ的非规范支架作用，从而将TRPV4-PI3Kγ复合物募集到质膜上，从而增加了成肌纤维细胞的转分化作用。鉴于TRPV4和PI3Kγ都具有多效作用，