Watts R G
Department of Pediatrics, University of Alabama at Birmingham 35233, USA.
Hematopathol Mol Hematol. 1996;10(4):223-32.
The F-actin based microfilamentous cytoskeleton (MFC) provides mobility for phagocytic immune cells including polymorphonuclear leukocytes (PMNs) and macrophages (MOs). In PMNs in suspension, the MFC is organized into two distinct F-actin pools [Triton Insoluble F-actin-(TIF), which form the sub-membranous, 3D actin meshwork and Triton Soluble F-actin (TSF), which exists as short oligomers] in equilibrium with G-actin. The structure of F-actin pools in adherent cells is unknown despite the fact that phagocytes are adherent in tissues in vivo. In order to determine the structure of F-actin pools in adherent phagocytes, human PMNs were isolated and allowed to adhere to plastic for 1 hour at 37 degrees C. Adherent cells were collected, actin pools separated and quantified by SDS-PAGE and compared to nonadherent PMNs in suspension. Likewise, the nonadherent human myeloid cell line U937 was induced to MO morphology and adherence by exposure to TPA (10(-6) M x 3 days) and similarly evaluated. Adherence of PMNs to plastic resulted in 75 +/- 15% adherence (n = 3). TPA differentiation of U937 cells resulted in 81 +/- 15% adherence (n = 10). In both cells, adherence resulted in a statistically significant increase in TIF, a decrease in TSF, and little to no change in G-actin. Basal, nonadherent PMNs in suspension contain TIF 40 +/- 0%, TSF 20 +/- 4%, and G-actin 40 +/- 4%, n = 3, whereas adherent PMNs contain TIF 61 +/- 3%, TSF 5 +/- 5%, G-actin 34 +/- 1%, n = 3. Basal U937 contain TIF 41 +/- 9%, TSF 17 +/- 6%, and G-actin 42 +/- 13%, n = 7. Adherent MO-like U937 contain TIF 53 +/- 4%, TSF 9 +/- 5%, and G-actin 38 +/- 4%. The results show that phagocyte adherence leads to a characteristic reorganization of actin pool structure that is remarkably quantitatively similar to, yet mechanistically distinct from, reorganization by chemotactic factor activation in suspension. Adherence-induced TIF-actin growth results exclusively from conversion of TSF-actin to TIF-actin.
基于F-肌动蛋白的微丝细胞骨架（MFC）为包括多形核白细胞（PMN）和巨噬细胞（MO）在内的吞噬免疫细胞提供移动性。在悬浮的PMN中，MFC被组织成两个不同的F-肌动蛋白池[Triton不溶性F-肌动蛋白-（TIF），形成膜下三维肌动蛋白网络；Triton可溶性F-肌动蛋白（TSF），以短寡聚体形式存在]，与G-肌动蛋白处于平衡状态。尽管吞噬细胞在体内组织中是粘附的，但粘附细胞中F-肌动蛋白池的结构尚不清楚。为了确定粘附吞噬细胞中F-肌动蛋白池的结构，分离人PMN并使其在37℃下粘附于塑料1小时。收集粘附细胞，通过SDS-PAGE分离并定量肌动蛋白池，并与悬浮的非粘附PMN进行比较。同样，非粘附的人髓系细胞系U937通过暴露于TPA（10^(-6) M×3天）诱导为MO形态并粘附，并进行类似评估。PMN对塑料的粘附导致75±15%的粘附率（n = 3）。U937细胞的TPA分化导致81±15%的粘附率（n = 10）。在这两种细胞中，粘附导致TIF在统计学上显著增加，TSF减少，G-肌动蛋白几乎没有变化或没有变化。悬浮的基础非粘附PMN含有40±0%的TIF、20±4%的TSF和40±4% 的G-肌动蛋白，n = 3，而粘附的PMN含有61±3%的TIF、5±5%的TSF、34±1%的G-肌动蛋白，n = 3。基础U937含有41±9%的TIF、17±6%的TSF和42±13%的G-肌动蛋白，n = 7。粘附的MO样U937含有53±4%的TIF、9±5%的TSF和38±4%的G-肌动蛋白。结果表明，吞噬细胞粘附导致肌动蛋白池结构发生特征性重组，在数量上与悬浮中趋化因子激活引起的重组非常相似，但机制不同。粘附诱导的TIF-肌动蛋白生长完全源于TSF-肌动蛋白向TIF-肌动蛋白的转化。
