KRIT1 is a scaffolding protein that regulates multiple molecular mechanisms, including cell–cell and cell–matrix adhesion, and redox homeostasis and signaling. However, rather little is known about how KRIT1 is itself regulated. KRIT1 is found in both the cytoplasm and the nucleus, yet the upstream signaling proteins and mechanisms that regulate KRIT1 nucleocytoplasmic shuttling are not well understood. Here, we identify a key role for protein kinase C (PKC) in this process. In particular, we found that PKC activation promotes the redox-dependent cytoplasmic localization of KRIT1, whereas inhibition of PKC or treatment with the antioxidant N-acetylcysteine leads to KRIT1 nuclear accumulation. Moreover, we demonstrated that the N-terminal region of KRIT1 is crucial for the ability of PKC to regulate KRIT1 nucleocytoplasmic shuttling, and may be a target for PKC-dependent regulatory phosphorylation events. Finally, we found that silencing of PKCα, but not PKC, inhibits phorbol 12-myristate 13-acetate (PMA)-induced cytoplasmic enrichment of KRIT1, suggesting a major role for PKCα in regulating KRIT1 nucleocytoplasmic shuttling. Overall, our findings identify PKCα as a novel regulator of KRIT1 subcellular compartmentalization, thus shedding new light on the physiopathological functions of this protein.

KRIT1 是一种支架蛋白，可调节多种分子机制，包括细胞-细胞和细胞-基质粘附、氧化还原稳态和信号传导。然而，人们对 KRIT1 本身的监管方式知之甚少。KRIT1 存在于细胞质和细胞核中，但调节 KRIT1 核质穿梭的上游信号蛋白和机制尚不清楚。在这里，我们确定了蛋白激酶 C (PKC) 在此过程中的关键作用。特别是，我们发现 PKC 激活促进 KRIT1 氧化还原依赖性细胞质定位，而抑制 PKC 或用抗氧化剂 N-乙酰半胱氨酸处理会导致 KRIT1 核积累。此外，我们证明 KRIT1 的 N 末端区域对于 PKC 调节 KRIT1 核质穿梭的能力至关重要，并且可能是 PKC 依赖性调节磷酸化事件的靶标。最后，我们发现沉默 PKCα（而非 PKC）会抑制佛波醇 12-肉豆蔻酸酯 13-乙酸酯 (PMA) 诱导的 KRIT1 细胞质富集，这表明 PKCα 在调节 KRIT1 核细胞质穿梭中起主要作用。总的来说，我们的研究结果确定 PKCα 是 KRIT1 亚细胞区室化的新型调节因子，从而为该蛋白质的病理生理功能提供了新的线索。