Allen L H, Aderem A
Laboratory of Signal Transduction, Rockefeller University, New York 10021, USA.
J Exp Med. 1995 Sep 1;182(3):829-40. doi: 10.1084/jem.182.3.829.
Myristoylated, alanine-rich C-kinase substrate (MARCKS) is a lipopolysaccharide-induced protein kinase C (PKC) substrate that has been proposed to regulate actin-membrane interactions, as well as actin structure at the membrane. We studied the distribution of MARCKS, the alpha isozyme of PKC (PKC alpha), and myosin I in lipopolysaccharide-treated peritoneal macrophages ingesting zymosan particles. MARCKS, PKC alpha, and myosin I colocalized with F-actin and talin in the cortical cytoplasm adjacent to forming phagocytic cups. After particle ingestion was completed, myosin I, F-actin, and talin were no longer enriched in the vicinity of the phagosome. By contrast, MARCKS and PKC alpha remained associated with the phagosome membrane until after acquisition of the lysosomal marker Lamp-1. Vinculin was not detected on phagosomes at any time point examined. Phagocytosis of zymosan was accompanied by rapid and sustained phosphorylation of MARCKS. Inhibitors of PKC reduced zymosan binding to the macrophage surface and blocked the focal accumulation of F-actin, talin, phosphotyrosine-containing proteins, MARCKS, and PKC alpha beneath attached particles. We propose that PKC-dependent phosphorylation is an early signal required for zymosan phagocytosis and that MARCKS and PKC alpha have a role in phagosome maturation. The colocalization of F-actin and MARCKS at the cytoplasmic face of the nascent phagosome reinforces the hypothesis that MARCKS regulates actin structure at the membrane. Our data also suggest that myosin I functions as a mechanical motor during particle uptake.
肉豆蔻酰化富含丙氨酸的蛋白激酶C底物（MARCKS）是一种脂多糖诱导的蛋白激酶C（PKC）底物，有人提出它可调节肌动蛋白与膜的相互作用以及膜上的肌动蛋白结构。我们研究了MARCKS、PKC的α同工酶（PKCα）和肌球蛋白I在摄取酵母聚糖颗粒的脂多糖处理的腹膜巨噬细胞中的分布。MARCKS、PKCα和肌球蛋白I与F-肌动蛋白和踝蛋白在靠近形成吞噬杯的皮质细胞质中共定位。颗粒摄取完成后，肌球蛋白I、F-肌动蛋白和踝蛋白在吞噬体附近不再富集。相比之下，MARCKS和PKCα在获得溶酶体标志物Lamp-1之前一直与吞噬体膜结合。在任何检测的时间点，吞噬体上均未检测到纽蛋白。酵母聚糖的吞噬作用伴随着MARCKS的快速持续磷酸化。PKC抑制剂减少了酵母聚糖与巨噬细胞表面的结合，并阻断了附着颗粒下方F-肌动蛋白、踝蛋白、含磷酸酪氨酸蛋白、MARCKS和PKCα的局部聚集。我们提出PKC依赖性磷酸化是酵母聚糖吞噬作用所需的早期信号，并且MARCKS和PKCα在吞噬体成熟中起作用。F-肌动蛋白和MARCKS在新生吞噬体细胞质面的共定位强化了MARCKS调节膜上肌动蛋白结构的假说。我们的数据还表明肌球蛋白I在颗粒摄取过程中起机械马达的作用。
