Actin-dependent leukocyte trafficking and activation are critical for immune surveillance under steady state conditions and during disease states. Proper immune surveillance is of utmost importance in mammalian homeostasis and it ensures the defense against pathogen intruders, but it also guarantees tissue integrity through the continuous removal of dying cells or the elimination of tumor cells. On the cellular level, these processes depend on the precise reorganization of the actin cytoskeleton orchestrating, e.g., cell polarization, migration, and vesicular dynamics in leukocytes. The fine-tuning of the actin cytoskeleton is achieved by a multiplicity of actin-binding proteins inducing, e.g., the organization of the actin cytoskeleton or linking the cytoskeleton to membranes and their receptors. More than a decade ago, the family of leucine-rich repeat (LRR) and calponin homology (CH) domain-containing (LRCH) proteins has been identified as cytoskeletal regulators. The LRR domains are important for protein-protein interactions and the CH domains mediate actin binding. LRR and CH domains are frequently found in many proteins, but strikingly the simultaneous expression of both domains in one protein only occurs in the LRCH protein family. To date, one LRCH protein has been described in drosophila and four LRCH proteins have been identified in the murine and the human system. The function of LRCH proteins is still under investigation. Recently, LRCH proteins have emerged as novel players in leukocyte function. In this review, we summarize our current understanding of LRCH proteins with a special emphasis on their function in leukocyte biology.

肌动蛋白依赖性白细胞的运输和激活对于稳定状态和疾病状态下的免疫监视至关重要。适当的免疫监视在哺乳动物体内平衡中至关重要，它可以确保对病原体入侵者的防御能力，但也可以通过连续去除垂死细胞或消除肿瘤细胞来保证组织完整性。在细胞水平上，这些过程取决于肌动蛋白细胞骨架的精确重组，例如白细胞中的细胞极化，迁移和囊泡动力学。肌动蛋白细胞骨架的微调是通过多种肌动蛋白结合蛋白来实现的，这些蛋白诱导例如肌动蛋白细胞骨架的组织或将细胞骨架与膜及其受体连接。十多年前 富含亮氨酸的重复序列（LRR）和含钙钙蛋白同源（CH）结构域（LRCH）的蛋白质家族已被确定为细胞骨架调节剂。LRR结构域对于蛋白质间相互作用非常重要，而CH结构域介导肌动蛋白结合。LRR和CH结构域经常出现在许多蛋白质中，但令人惊讶的是，一个蛋白质中两个结构域的同时表达仅发生在LRCH蛋白家族中。迄今为止，在果蝇中已经描述了一种LRCH蛋白，并且在鼠和人系统中已经鉴定出四种LRCH蛋白。LRCH蛋白的功能仍在研究中。最近，LRCH蛋白已成为白细胞功能的新参与者。在这篇综述中，我们总结了我们对LRCH蛋白的当前理解，并特别强调了它们在白细胞生物学中的功能。