The dynamic organization of the actin cytoskeleton into bundles and networks is orchestrated by a large variety of actin-binding proteins. Among them, the actin-bundling protein L-plastin is normally expressed in hematopoietic cells, where it is involved in the immune response. However, L-plastin is also often ectopically expressed in malignant cancer cells of non-hematopoietic origin and is even considered as a marker for cancer progression. Post-translational modification modulates L-plastin activity. In particular, L-plastin Ser5 phosphorylation has been shown to be important for the immune response in leukocytes as well as for invasion and metastasis formation of carcinoma cells.

This chapter discusses the physiological and pathological role of L-plastin with a special focus on the importance of L-plastin Ser5 phosphorylation for the protein functions. The potential use of Ser5 phosphorylated L-plastin as a biomarker and/or therapeutic target will be evoked.

肌动蛋白细胞骨架动态组织成束和网络是由多种肌动蛋白结合蛋白协调的。其中，肌动蛋白捆绑蛋白 L-plastin 通常在造血细胞中表达，参与免疫反应。然而，L-plastin 也经常在非造血来源的恶性癌细胞中异位表达，甚至被认为是癌症进展的标志物。翻译后修饰调节 L-plastin 活性。特别是，L-plastin Ser5 磷酸化已被证明对白细胞的免疫反应以及癌细胞的侵袭和转移形成很重要。

本章讨论 L-plastin 的生理和病理作用，特别关注 L-plastin Ser5 磷酸化对蛋白质功能的重要性。将引发 Ser5 磷酸化 L-plastin 作为生物标志物和/或治疗靶标的潜在用途。