FGF2 is a tumor cell survival factor that is exported from cells by an ER/Golgi-independent secretory pathway. This unconventional mechanism of protein secretion is based on direct translocation of FGF2 across the plasma membrane. The Na,K-ATPase has previously been shown to play a role in this process, however, the underlying mechanism has remained elusive. Here, we define structural elements that are critical for a direct physical interaction between FGF2 and the α1 subunit of the Na,K-ATPase. In intact cells, corresponding FGF2 mutant forms were impaired regarding both recruitment at the inner plasma membrane leaflet and secretion. Ouabain, a drug that inhibits both the Na,K-ATPase and FGF2 secretion, was found to impair the interaction of FGF2 with the Na,K-ATPase in cells. Our findings reveal the Na,K-ATPase as the initial recruitment factor for FGF2 at the inner plasma membrane leaflet being required for efficient membrane translocation of FGF2 to cell surfaces.

FGF2 是一种肿瘤细胞存活因子，通过不依赖 ER/高尔基体的分泌途径从细胞中输出。这种非常规的蛋白质分泌机制基于 FGF2 跨质膜的直接易位。Na,K-ATPase 先前已被证明在此过程中发挥作用，然而，潜在的机制仍然难以捉摸。在这里，我们定义了对 FGF2 和 Na,K-ATPase 的 α1 亚基之间的直接物理相互作用至关重要的结构元件。在完整细胞中，相应的 FGF2 突变体在内质膜小叶的募集和分泌方面均受损。哇巴因是一种抑制 Na,K-ATPase 和 FGF2 分泌的药物，被发现会削弱 FGF2 与细胞中 Na,K-ATPase 的相互作用。我们的研究结果揭示了 Na，