ALK1 signaling is required for the homeostasis of Kupffer cells and prevention of bacterial infection

• Published in: The Journal of clinical investigation Vol. 132; no. 3; pp. 1 - 15
• Main Authors: Zhao, Dianyuan, Yang, Fengjiao, Wang, Yang, Li, Site, Li, Yang, Hou, Fei, Yang, Wenting, Liu, Di, Tao, Yuandong, Li, Qian, Wang, Jing, He, Fuchu, Tang, Li
• Format: Journal Article
• Language: English
• Published: United States American Society for Clinical Investigation 01.02.2022
• Subjects: Activin; Activin Receptors, Type II - genetics; Activin Receptors, Type II - metabolism; Animals; Bacteria; Bacterial infections; Biomedical research; Bone Morphogenetic Proteins - genetics; Bone Morphogenetic Proteins - metabolism; Flow cytometry; Gene expression; Genomics; Genotype & phenotype; Growth Differentiation Factor 2 - genetics; Growth Differentiation Factor 2 - metabolism; Growth factor receptors; Health aspects; Homeostasis; Hypotheses; Immune response; Immune system; Immunology; Kinases; Kupffer cells; Kupffer Cells - enzymology; Listeria; Listeria monocytogenes; Listeria monocytogenes - metabolism; Listeriosis - enzymology; Listeriosis - genetics; Listeriosis - prevention & control; Liver; Macrophages; Mice; Mice, Knockout; Monocytes; Phenotypes; Physiological aspects; Prevention; Signal Transduction; Smad4 protein; Spleen; Zonation; China; Macrophages; Immunology
• ISSN: 1558-8238; 0021-9738; 1558-8238
• DOI: 10.1172/JCI150489

Macrophages are highly heterogeneous immune cells that fulfill tissue-specific functions. Tissue-derived signals play a critical role in determining macrophage heterogeneity. However, these signals remain largely unknown. The BMP receptor activin receptor-like kinase 1 (ALK1) is well known for its role in blood vessel formation; however, its role within the immune system has never been revealed to our knowledge. Here, we found that BMP9/BMP10/ALK1 signaling controlled the identity and self-renewal of Kupffer cells (KCs) through a Smad4-dependent pathway. In contrast, ALK1 was dispensable for the maintenance of macrophages located in the lung, kidney, spleen, and brain. Following ALK1 deletion, KCs were lost over time and were replaced by monocyte-derived macrophages. These hepatic macrophages showed significantly reduced expression of the complement receptor VSIG4 and alterations in immune zonation and morphology, which is important for the tissue-specialized function of KCs. Furthermore, we found that this signaling pathway was important for KC-mediated Listeria monocytogenes capture, as the loss of ALK1 and Smad4 led to a failure of bacterial capture and overwhelming disseminated infections. Thus, ALK1 signaling instructs a tissue-specific phenotype that allows KCs to protect the host from systemic bacterial dissemination.