Johnson Katherine M, Marley Maxwell G, Drizyte-Miller Kristina, Chen Jing, Cao Hong, Mostafa Nourhan, Schott Micah B, McNiven Mark A, Razidlo Gina L
Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905.
Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905.
Proc Natl Acad Sci U S A. 2025 Apr 29;122(17):e2502971122. doi: 10.1073/pnas.2502971122. Epub 2025 Apr 21.
Rab32 is a small GTPase and molecular switch implicated in vesicular trafficking. Rab32 is also an A-Kinase Anchoring Protein (AKAP), which anchors cAMP-dependent Protein Kinase (PKA) to specific subcellular locations and specifies PKA phosphorylation of nearby substrates. Surprisingly, we found that a form of Rab32 deficient in PKA binding (Rab32 L188P) relocalized away from the Golgi apparatus and induced a marked disruption in Golgi organization, assembly, and dynamics. Although Rab32 L188P did not cause a global defect in PKA activity, our data indicate that Rab32 facilitates the phosphorylation of a specific PKA substrate. We uncovered a direct interaction between Rab32 and the adaptor protein optineurin (OPTN), which regulates Golgi dynamics. Further, our data indicate that optineurin is phosphorylated by PKA at Ser342 in a Rab32-dependent manner. Critically, blocking phosphorylation at OPTN Ser342 leads to Golgi fragmentation, and a phospho-mimetic version of OPTN rescues Golgi defects induced by Rab32 L188P. Finally, Rab32 AKAP function and OPTN phosphorylation are required for Golgi repositioning during cell migration, contributing to tumor cell invasion. Together, these data reveal a role for Rab32 in regulating Golgi dynamics through PKA-mediated phosphorylation of OPTN.
Rab32是一种参与囊泡运输的小GTP酶和分子开关。Rab32也是一种A激酶锚定蛋白（AKAP），它将环磷酸腺苷依赖性蛋白激酶（PKA）锚定到特定的亚细胞位置，并指定PKA对附近底物的磷酸化。令人惊讶的是，我们发现一种缺乏PKA结合能力的Rab32形式（Rab32 L188P）从高尔基体重新定位，并导致高尔基体组织、组装和动力学的明显破坏。虽然Rab32 L188P没有导致PKA活性的全局性缺陷，但我们的数据表明Rab32促进了特定PKA底物的磷酸化。我们发现Rab32与调节高尔基体动力学的衔接蛋白视黄醛结合蛋白（OPTN）之间存在直接相互作用。此外，我们的数据表明视黄醛结合蛋白在Rab32依赖性的Ser342位点被PKA磷酸化。至关重要的是，阻断视黄醛结合蛋白Ser342位点的磷酸化会导致高尔基体碎片化，而视黄醛结合蛋白的磷酸化模拟版本可挽救由Rab32 L188P诱导的高尔基体缺陷。最后，Rab32的AKAP功能和视黄醛结合蛋白的磷酸化是细胞迁移过程中高尔基体重新定位所必需的，有助于肿瘤细胞侵袭。总之，这些数据揭示了Rab32在通过PKA介导的视黄醛结合蛋白磷酸化来调节高尔基体动力学中的作用。
