Biology and Microbiology Department, South Dakota State University, Brookings, SD 57007.
Chemistry, Biochemistry and Physics Department, South Dakota State University, Brookings, SD 57007.
Mol Biol Cell. 2024 Dec 1;35(12):ar153. doi: 10.1091/mbc.E24-08-0355. Epub 2024 Nov 6.
Macrophages survey their environment using receptor-mediated endocytosis and pinocytosis. Receptor-mediated endocytosis allows internalization of specific ligands, whereas pinocytosis nonselectively internalizes extracellular fluids and solutes. CRISPR/Cas9 whole-genome screens were used to identify genes regulating constitutive and growth factor-stimulated dextran uptake in murine bone marrow-derived macrophages (BMDM). The mannose receptor c-type 1 (MRC1/CD206) was a top hit in the screen. Targeted gene disruptions of reduced dextran uptake but had little effect on fluid-phase uptake of Lucifer yellow. Other screen hits also differentially affected the uptake of dextran and Lucifer yellow, indicating internalization by separate mechanisms. Visualization of dextran and Lucifer yellow uptake by microscopy showed enrichment of dextran in small puncta, which was inhibitable by mannan, a ligand of MRC1. In contrast, Lucifer yellow predominantly was internalized in larger macropinosomes In addition, IL4-treated BMDMs internalized more dextran than untreated BMDM correlating with increased MRC1 expression. Therefore, dextran is not an effective marker for pinocytosis in BMDMs since it is internalized by receptor-mediated process. Numerous genes that regulate dextran internalization in primary murine macrophages were identified in the whole-genome screens, which can inform understanding of the regulation of MRC1 expression and MRC1-mediated uptake in macrophages.
巨噬细胞通过受体介导的内吞作用和胞饮作用来检测其周围环境。受体介导的内吞作用允许特定配体的内化，而胞饮作用则非选择性地内化细胞外液和溶质。CRISPR/Cas9 全基因组筛选用于鉴定调节小鼠骨髓来源的巨噬细胞 (BMDM) 中组成型和生长因子刺激的葡聚糖摄取的基因。甘露糖受体 C 型 1 (MRC1/CD206) 在筛选中是一个重要的命中靶点。该基因的靶向基因敲除减少了葡聚糖的摄取，但对 Lucifer yellow 的流体相摄取几乎没有影响。其他筛选命中也对葡聚糖和 Lucifer yellow 的摄取有不同的影响，表明它们通过不同的机制内化。通过显微镜观察葡聚糖和 Lucifer yellow 的摄取显示，葡聚糖在小斑点中富集，甘露聚糖可以抑制其摄取，甘露聚糖是 MRC1 的配体。相比之下， Lucifer yellow 主要被内化到较大的巨胞饮体中。此外，与未经处理的 BMDM 相比，经 IL4 处理的 BMDM 摄取更多的葡聚糖，这与 MRC1 表达增加有关。因此，葡聚糖不是 BMDM 中胞饮作用的有效标志物，因为它是通过受体介导的过程内化的。在全基因组筛选中鉴定了许多调节原代小鼠巨噬细胞中葡聚糖内化的基因，这可以帮助我们理解 MRC1 表达和 MRC1 介导的巨噬细胞摄取的调节。
