Actinin-4 is preferentially involved in circular ruffling and macropinocytosis in mouse macrophages: analysis by fluorescence ratio imaging.
Actinin-4 is preferentially involved in circular ruffling and macropinocytosis in mouse macrophages: analysis by fluorescence ratio imaging.
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发表时间：
2000-09
影响因子：
4
通讯作者：
N. Araki;T. Hatae;T. Yamada;S. Hirohashi
中科院分区：
文献类型：
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作者：
N. Araki;T. Hatae;T. Yamada;S. Hirohashi
我们已经应用荧光比率成像的肌动蛋白结合蛋白的浓度相对于F-肌动蛋白在巨噬细胞中的分析，以探讨一种新的（α）-肌动蛋白亚型，肌动蛋白-4，相对于经典的亚型，肌动蛋白-1的作用。传统的免疫荧光图像显示，这两种亚型都富含F-肌动蛋白丰富的区域，如细胞表面皱褶。然而，比率图像进一步表明，辅肌动蛋白-4浓度相对于F-肌动蛋白较高，在周边向内弯曲的皱褶和背侧圆形皱褶，推定的前体形式的macropinosome，比直线型皱褶，而辅肌动蛋白-1浓度是均匀的不同类型的皱褶。大胞饮体脉冲标记和追踪实验表明，actinin-4也与新形成的大胞饮体密切相关，并随着它们的成熟而逐渐解离。与比率成像数据一致，负载抗辅肌动蛋白-4的巨噬细胞刮片显示出比负载抗辅肌动蛋白-1的巨噬细胞更低的巨胞饮速率。总之，这些结果表明，辅肌动蛋白-4和辅肌动蛋白-1有助于不同的F-肌动蛋白动力学，辅肌动蛋白-4更优先参与的早期阶段的巨胞饮比辅肌动蛋白-1。在吞噬过程中也观察到类似的再分配辅肌动蛋白-4，表明辅肌动蛋白-4可能在两种机制类似的内吞作用中发挥相同的作用，即巨胞饮和吞噬作用。
We have applied fluorescence ratio imaging to the analysis of an actin-binding protein concentration relative to F-actin in macrophages, in order to explore the role of a novel (alpha)-actinin isoform, actinin-4, relative to that of the classical isoform, actinin-1. Conventional immunofluorescence images showed that both isoforms were enriched in F-actin-rich regions such as cell surface ruffles. However, ratio images further demonstrated that actinin-4 concentrations relative to F-actin were higher in peripheral inward curved ruffles and dorsal circular ruffles, presumed precursor forms of macropinosomes, than in straight linear ruffles, while actinin-1 concentrations were uniform among the different types of ruffles. Macropinosome pulse-labeling and chase experiments indicated that actinin-4 was also closely associated with newly formed macropinosomes and gradually dissociated with their maturation. Consistent with ratio imaging data, macrophages scrape-loaded with anti-actinin-4 showed a more reduced rate of macropinocytosis than those loaded with anti-actinin-1. Altogether, these results indicate that actinin-4 and actinin-1 contribute differently to F-actin dynamics, that actinin-4 is more preferentially involved in early stages of macropinocytosis than actinin-1. A similar redistribution of actinin-4 was also observed during phagocytosis, suggesting that actinin-4 may play the same role in the two mechanistically analogous types of endocytosis, i.e. macropinocytosis and phagocytosis.