Watts R G, Howard T H
Department of Pediatrics, University of Alabama, Birmingham 35233.
Blood. 1993 May 15;81(10):2750-7.
Cytoskeletal structure in polymorphonuclear leukocytes (PMNs) is thought to reflect a simple equilibrium between two actin pools (globular [G]- and filamentous [F] actin). Recent description of two distinct F-actin pools in PMNs (Triton-insoluble [stable] and Triton-soluble [labile] F-actin pools) (Watts and Howard, Cell Motil Cytoskeleton, 21:25, 1992) suggest a tripartite equilibrium between these F-actin pools and G-actin and multiple possible mechanisms for polymerization. To study the contribution of each actin pool to actin dynamics in PMNs, changes in actin content of the Triton-soluble and -insoluble F-actin pools and G-actin in chemotactic factor (CTF)-activated PMNs were measured by NBDphallacidin binding and by gel scans of Triton-lysed PMNs. From 0 to 30 seconds after CTF activation, PMNs rapidly increase total (Triton-soluble + Triton-insoluble) F-actin content (maximum = 1.7- +/- 0.10-fold basal at 30 seconds). Concurrent measures of the actin content of individual actin pools (Triton-soluble and -insoluble F-actin and G-actin) show that at all times (0 to 30 seconds) only the Triton-insoluble F-actin pool grows (maximum = 2.81- +/- 0.73-fold basal at 30 seconds), whereas both the Triton-soluble and G-actin pools simultaneously decrease (50% decrease at 30 seconds). Concurrent growth of one F-actin pool (Triton-insoluble) and loss of another F-actin pool (Triton-soluble) emphasize the functional uniqueness of the F-actin pools and can occur only if the Triton-soluble F-actin anneals or cross-links filament-to-filament with the Triton-insoluble fraction or if the Triton-insoluble F-actin pool first depolymerizes to monomer, which is then added to the Triton-insoluble pool. Because from 0 to 30 seconds after FMLP activation G-actin never increases, but, like the Triton-soluble F-actin progressively decreases, the results suggest that F-actin growth results from simultaneous new filament growth by monomer addition to the Triton-insoluble F-actin and cytoskeletal remodelling by Triton-soluble F-actin annealing or cross-linking to Triton-insoluble F-actin. These findings offer important new insights into the mechanism(s) of actin polymerization in CTF-activated human PMNs.
多形核白细胞（PMNs）中的细胞骨架结构被认为反映了两个肌动蛋白池（球状[G] - 和丝状[F]肌动蛋白）之间的简单平衡。最近对PMNs中两个不同的F - 肌动蛋白池（Triton不溶性[稳定]和Triton可溶性[不稳定] F - 肌动蛋白池）的描述（Watts和Howard，《细胞运动与细胞骨架》，21:25，1992）表明这些F - 肌动蛋白池与G - 肌动蛋白之间存在三方平衡以及多种可能的聚合机制。为了研究每个肌动蛋白池对PMNs中肌动蛋白动力学的贡献，通过NBD鬼笔环肽结合以及对Triton裂解的PMNs进行凝胶扫描，测量趋化因子（CTF）激活的PMNs中Triton可溶性和不溶性F - 肌动蛋白池以及G - 肌动蛋白的肌动蛋白含量变化。在CTF激活后的0到30秒内，PMNs迅速增加总（Triton可溶性+ Triton不溶性）F - 肌动蛋白含量（30秒时最大值=基础值的1.7±0.10倍）。对各个肌动蛋白池（Triton可溶性和不溶性F - 肌动蛋白以及G - 肌动蛋白）的肌动蛋白含量的同时测量表明，在所有时间（0到30秒），只有Triton不溶性F - 肌动蛋白池增加（30秒时最大值=基础值的2.81±0.73倍），而Triton可溶性和G - 肌动蛋白池同时减少（30秒时减少50%）。一个F - 肌动蛋白池（Triton不溶性）的同时增加和另一个F - 肌动蛋白池（Triton可溶性）的减少强调了F - 肌动蛋白池的功能独特性，并且只有在Triton可溶性F - 肌动蛋白与Triton不溶性部分进行丝对丝退火或交联，或者Triton不溶性F - 肌动蛋白池首先解聚为单体然后添加到Triton不溶性池中时才会发生。因为在FMLP激活后的0到30秒内G - 肌动蛋白从未增加，而是像Triton可溶性F - 肌动蛋白一样逐渐减少，结果表明F - 肌动蛋白的增加是由于通过向Triton不溶性F - 肌动蛋白添加单体同时进行新丝生长以及Triton可溶性F - 肌动蛋白与Triton不溶性F - 肌动蛋白退火或交联进行细胞骨架重塑。这些发现为CTF激活的人PMNs中肌动蛋白聚合机制提供了重要的新见解。
