Knapp P E, Swanson J A
Department of Anatomy and Cellular Biology, Harvard Medical School, Boston, MA 02115.
J Cell Sci. 1990 Mar;95 ( Pt 3):433-9. doi: 10.1242/jcs.95.3.433.
Because bone marrow-derived macrophages differentiate in culture, their lysosomal compartment is largely devoid of the undigested particles that are common in macrophages removed from tissues. The morphology of this nearly vacant lysosomal compartment was observed, after labeling with fluorescent endocytic tracers such as Lucifer Yellow, to be an extensive, tubuloreticular network, which underwent extensive rearrangements in accommodating endocytic loads. It was converted to spherical organelles when the lysosomal compartment was loaded with osmotically active solutes such as sucrose or Acridine Orange. Enzymatic degradation of intravacuolar sucrose by pinocytosed invertase resulted in the shrinkage of vacuoles and the re-formation of the tubular network. After phagocytosis of opsonized erythrocytes or latex beads, tubular lysosomes wrapped around the phagosomes, then merged to form phagolysosomes. The disappearance of tubules was proportional to the total surface area of particles ingested. Degradation of the phagocytosed contents permitted shrinkage of the phagolysosome and concomitant re-formation of the tubuloreticular network. Nondegradable contents such as latex beads prevented re-formation of the tubular network. These rearrangements of the lysosomal compartment indicate that the organelle exhibits considerable plasticity and interconnectedness, and that maturation of lysosomes after endocytosis does not necessarily entail irreversible morphological changes.
由于骨髓来源的巨噬细胞在培养中分化，其溶酶体区室在很大程度上没有从组织中分离出的巨噬细胞中常见的未消化颗粒。在用荧光内吞示踪剂（如荧光黄）标记后，观察到这个几乎空的溶酶体区室的形态是一个广泛的管状网状网络，它在容纳内吞负载时经历了广泛的重排。当溶酶体区室装载有渗透活性溶质（如蔗糖或吖啶橙）时，它会转变为球形细胞器。通过胞饮作用摄取的转化酶对液泡内蔗糖的酶促降解导致液泡收缩和管状网络的重新形成。在吞噬调理素化的红细胞或乳胶珠后，管状溶酶体包裹吞噬体，然后融合形成吞噬溶酶体。小管的消失与摄取颗粒的总表面积成正比。吞噬内容物的降解允许吞噬溶酶体收缩并伴随管状网状网络的重新形成。不可降解的内容物（如乳胶珠）阻止了管状网络的重新形成。溶酶体区室的这些重排表明该细胞器表现出相当大的可塑性和相互连接性，并且内吞作用后溶酶体的成熟不一定需要不可逆的形态变化。
