Mammalian cell cytoskeletal reorganization for efficient directional movement requires tight coordination of actomyosin and microtubule networks. In this study, we show that LRAP35a potentiates microtubule stabilization by promoting CLASP2/EB1 interaction besides its complex formation with MRCK/MYO18A for retrograde actin flow. The alternate regulation of these two networks by LRAP35a is tightly regulated by a series of phosphorylation events that dictated its specificity. Sequential phosphorylation of LRAP35a by Protein Kinase A (PKA) and Glycogen Synthase Kinase-3β (GSK3β) initiates the association of LRAP35a with CLASP2, while subsequent binding and further phosphorylation by Casein Kinase 1δ (CK1δ) induce their dissociation, which facilitates LRAP35a/MRCK association in driving lamellar actomyosin flow. Importantly, microtubule dynamics is directly moderated by CK1δ activity on CLASP2 to regulate GSK3β phosphorylation of the SxIP motifs that blocks EB1 binding, an event countered by LRAP35a interaction and its competition for CK1δ activity. Overall this study reveals an essential role for LRAP35a in coordinating lamellar contractility and microtubule polarization in cell migration.

哺乳动物细胞骨架重组以实现有效的定向运动需要肌动球蛋白和微管网络的紧密协调。在这项研究中，我们发现 LRAP35a 除了与 MRCK/MYO18A 形成复杂的逆行肌动蛋白流动外，还通过促进 CLASP2/EB1 相互作用来增强微管的稳定性。LRAP35a 对这两个网络的交替调节受到一系列决定其特异性的磷酸化事件的严格调节。蛋白激酶 A (PKA) 和糖原合酶激酶-3β (GSK3β) 对 LRAP35a 的连续磷酸化启动 LRAP35a 与 CLASP2 的结合，而随后酪蛋白激酶 1δ (CK1δ) 的结合和进一步磷酸化诱导它们的解离，从而促进 LRAP35a/MRCK驱动层状肌动球蛋白流动的关联。重要的，CLASP2 上的 CK1δ 活性直接调节微管动力学，以调节阻断 EB1 结合的 SxIP 基序的 GSK3β 磷酸化，LRAP35a 相互作用及其对 CK1δ 活性的竞争抵消了这一事件。总的来说，这项研究揭示了 LRAP35a 在协调细胞迁移中的层状收缩性和微管极化方面的重要作用。