Daukas G, Zigmond S H
J Cell Biol. 1985 Nov;101(5 Pt 1):1673-9. doi: 10.1083/jcb.101.5.1673.
We have found that hypertonic medium inhibited the receptor-mediated uptake of the chemotactic peptide N-formylnorleucylleucylphenylalanine without affecting fluid-phase endocytosis by polymorphonuclear leukocytes (PMNs). Morphological and biochemical evidence demonstrated that cells in hypertonic medium did not accumulate peptide in a receptor-mediated manner. However, the cells continued to form endosomes containing fluid-phase markers. Furthermore, the content of these endosomes was processed normally, i.e., both digested and intact material were released into the medium. The inhibition of receptor-mediated uptake was a function of the tonicity. Partial inhibition occurred in 0.45 and 0.6 osmolar medium and maximal inhibition occurred in 0.75 osmolar medium. The inhibition was independent of the solute used to increase the tonicity: sodium chloride, sucrose, and lactose all inhibited uptake to similar extents. Hypertonic medium had little effect on saturable peptide binding. However, it did prevent the clustering of surface molecules as indicated by the inhibition of capping of fluorescent concanavalin A. In addition, hypertonic medium prevented the peptide-stimulated increase in cytosolic calcium levels as measured by quin 2 fluorescence. The tonicity dependence of the inhibition of quin 2 fluorescence paralleled the inhibition of receptor-mediated uptake.
我们发现,高渗介质可抑制趋化肽N-甲酰基去甲亮氨酰亮氨酰苯丙氨酸的受体介导摄取,而不影响多形核白细胞(PMN)的液相内吞作用。形态学和生物化学证据表明,处于高渗介质中的细胞不会以受体介导的方式积累肽。然而,细胞继续形成含有液相标记物的内体。此外,这些内体的内容物正常处理,即消化的和完整的物质都释放到介质中。受体介导摄取的抑制是张力的函数。在0.45和0.6渗透压介质中出现部分抑制,在0.75渗透压介质中出现最大抑制。这种抑制与用于增加张力的溶质无关:氯化钠、蔗糖和乳糖对摄取的抑制程度相似。高渗介质对可饱和肽结合影响很小。然而,如荧光伴刀豆球蛋白A帽化的抑制所示,它确实阻止了表面分子的聚集。此外, 高渗介质可防止通过喹啉2荧光测量的肽刺激的胞质钙水平升高。喹啉2荧光抑制的张力依赖性与受体介导摄取的抑制平行。