Song Ran, Ngoka Chigozie, Singla Amika, Kramer Daniel A, Diwaker Alka, Boesch Daniel J, Liu Qi, Moresco James J, Beutler Bruce, Reinecker Hans-Christian, Burstein Ezra, Chen Baoyu, Turer Emre E
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, 75390, USA.
Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology, Iowa State University, Ames, Iowa, 50011, USA.
bioRxiv. 2025 Jul 19:2025.07.16.665158. doi: 10.1101/2025.07.16.665158.
Maintaining intestinal homeostasis relies on the intricate interplay among the mucosal epithelium, immune system, and host microbiome. A key question is how innate immune cells sense and process microbes in the gut lumen, eliciting appropriate protective responses without causing tissue injury. Clearance of invading microbes and initiation of downstream inflammatory responses are central to this process and require proper function of the endolysosomal system. Dysfunction of this system can predispose the host to chronic inflammatory disorders and acute infections. Here, through forward genetic screening of N-ethyl-N-nitrosourea (ENU)-mutagenized mice and CRISPR/Cas9 validation, we identify , encoding leucine-rich melanocyte differentiation-associated protein (LRMDA), as a key regulator of intestinal homeostasis. Using hematopoietic chimera and conditional knockouts, we show that LRMDA functions primarily in CD11c cells, including mucosal dendritic cells (DCs) and macrophages, but not in non-hematopoietic cells. Proteomic, cellular, and biochemical analyses reveal that LRMDA directly and cooperatively interacts with the endolysosome-specific small GTPase Rab32 and the endosomal recycling complex Retriever. Loss of LRMDA or Retriever function increases susceptibility to dextran sodium sulfate (DSS)-induced colitis and impairs clearance of . Together, our findings establish the Rab32-LRMDA-Retriever complex as a critical regulator of endolysosomal trafficking in innate immune cells, essential for maintaining intestinal immune homeostasis.
维持肠道内稳态依赖于黏膜上皮、免疫系统和宿主微生物群之间复杂的相互作用。一个关键问题是先天免疫细胞如何感知和处理肠腔内的微生物，引发适当的保护性反应而不造成组织损伤。清除入侵微生物和启动下游炎症反应是这一过程的核心，需要内溶酶体系统的正常功能。该系统功能失调会使宿主易患慢性炎症性疾病和急性感染。在这里，通过对N-乙基-N-亚硝基脲（ENU）诱变小鼠进行正向遗传筛选和CRISPR/Cas9验证，我们鉴定出编码富含亮氨酸的黑素细胞分化相关蛋白（LRMDA）的 作为肠道内稳态的关键调节因子。利用造血嵌合体和条件性基因敲除，我们发现LRMDA主要在CD11c细胞中发挥作用，包括黏膜树突状细胞（DCs）和巨噬细胞，而不在非造血细胞中发挥作用。蛋白质组学、细胞和生化分析表明，LRMDA直接且协同地与内溶酶体特异性小GTP酶Rab32和内体回收复合体Retriever相互作用。LRMDA或Retriever功能丧失会增加对葡聚糖硫酸钠（DSS）诱导的结肠炎的易感性，并损害 的清除。总之，我们的研究结果确立了Rab32-LRMDA-Retriever复合体是先天免疫细胞内溶酶体运输的关键调节因子，对维持肠道免疫内稳态至关重要。
