Qi Yaoyue, Yu Cheng-Han
School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong.
Cell Mol Life Sci. 2025 Mar 24;82(1):127. doi: 10.1007/s00018-025-05664-2.
Podosomes are adhesion structures with densely-polymerized F-actin. While PI(3,4,5)P3 and Cdc42-GTP are known factors to trigger WASP-mediated actin polymerization at the macrophage podosome, their causal mechanism to activate WASP remains unclear. Here, we demonstrate that spatially elevated Cdc42-GTP is a downstream effector of local PI(3,4,5)P3 production at the podosome. We further examine the expression and distribution of 19 Cdc42 guanine exchange factors (GEFs) and identify VAV1 as the key PI(3,4,5)P3-dependent Cdc42 GEF. VAV1 is spatially enriched at the macrophage podosome, and the association of VAV1 with the membrane plays a critical role in upregulating its GEF activity. Reintroduction of wildtype VAV1, rather than the PI(3,4,5)P3-binding deficient or catalytically dead mutants restores the matrix degradation and chemotactic migration of VAV1-knockdown macrophage. Thus, the biogenesis of PI(3,4,5)P3 acts as an upstream signal to locally recruit VAV1 and in turn triggers the guanine nucleotide exchange of Cdc42. Elevated levels of Cdc42-GTP then promote WASP-mediated podosome assembly and macrophage chemotaxis.
足体是具有密集聚合的丝状肌动蛋白的粘附结构。虽然磷脂酰肌醇-3,4,5-三磷酸（PI(3,4,5)P3）和Cdc42-鸟苷三磷酸（Cdc42-GTP）是已知的在巨噬细胞足体处触发WASP介导的肌动蛋白聚合的因子，但其激活WASP的因果机制仍不清楚。在此，我们证明空间上升高的Cdc42-GTP是足体处局部PI(3,4,5)P3产生的下游效应物。我们进一步研究了19种Cdc42鸟嘌呤核苷酸交换因子（GEF）的表达和分布，并确定VAV1是关键的PI(3,4,5)P3依赖性Cdc42 GEF。VAV1在巨噬细胞足体处空间富集，并且VAV1与膜的结合在上调其GEF活性中起关键作用。重新引入野生型VAV1，而不是PI(3,4,5)P3结合缺陷型或催化失活突变体，可恢复VAV1敲低巨噬细胞的基质降解和趋化迁移。因此，PI(3,4,5)P3的生物合成作为上游信号局部招募VAV，并进而触发Cdc42的鸟嘌呤核苷酸交换。升高的Cdc42-GTP水平随后促进WASP介导的足体组装和巨噬细胞趋化性。
