Ghosh S, Khan S A, Wickstrom M, Beasley V
Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois, Urbana 61801, USA.
Nat Toxins. 1995;3(6):405-14. doi: 10.1002/nt.2620030602.
Microcystin-LR (MCLR) is a commonly encountered blue-green algal hepatotoxin and a known inhibitor of cellular protein phosphatase types 1 and 2A. The toxin causes alterations in, and redistribution of, intermediate filaments, microtubules, and actin microfilaments (MFs) in affected cells. In this study, the effect of MCLR on the sequence of alterations in MFs and actin-associated proteins (AAPs) of isolated hepatocytes was examined in an effort to determine whether morphologic changes induced in MFs by microcystins are a result of prior dislocation of AAPs. We studied the effects of MCLR exposure on alpha-actinin and talin, two AAPs that play a role in the orientation of the MFs. Primary hepatocytes were incubated with 10 microns MCLR for 0-64 min. The distribution of actin, alpha-actinin, and talin were examined using fluorescence microscopy. MCLR induced similar changes in the distribution of actin and the AAPs. Actin filament redistribution was first observed after 12 min of MCLR exposure, and was characterized by detachment of MFs from the cell periphery, followed by condensation at distinct focal points and progressive collapse into the interior of affected cells. Changes in alpha-actinin and talin distribution were first observed after 20 min of toxin exposure. The AAPs appeared to detach from focal contacts on the cytoplasmic surface of the plasma membrane, condense into cytoplasmic aggregates, and ultimately collapse into a juxtanuclear bundle. The results of this study indicate that, in hepatocytes exposed to MCLR, the collapse of actin MFs occurs prior to the dislocation of alpha-actinin and talin. Changes in these actin associated proteins are not likely to account for the initial changes in actin MFs.
微囊藻毒素-LR（MCLR）是一种常见的蓝藻肝毒素，也是已知的细胞1型和2A型蛋白磷酸酶抑制剂。该毒素会导致受影响细胞中的中间丝、微管和肌动蛋白微丝（MFs）发生改变和重新分布。在本研究中，检测了MCLR对分离的肝细胞中MFs和肌动蛋白相关蛋白（AAPs）变化顺序的影响，以确定微囊藻毒素诱导的MFs形态变化是否是AAPs先前错位的结果。我们研究了MCLR暴露对α-辅肌动蛋白和踝蛋白这两种在MFs定向中起作用的AAPs的影响。将原代肝细胞与10微摩尔的MCLR孵育0至64分钟。使用荧光显微镜检查肌动蛋白、α-辅肌动蛋白和踝蛋白的分布。MCLR诱导肌动蛋白和AAPs分布发生类似变化。在MCLR暴露12分钟后首次观察到肌动蛋白丝重新分布，其特征是MFs从细胞周边脱离，随后在不同的焦点处凝聚，并逐渐塌陷到受影响细胞内部。在毒素暴露20分钟后首次观察到α-辅肌动蛋白和踝蛋白分布的变化。AAPs似乎从质膜细胞质表面的粘着斑脱离，凝聚成细胞质聚集体，并最终塌陷成核旁束。本研究结果表明，在暴露于MCLR的肝细胞中，肌动蛋白MFs的塌陷发生在α-辅肌动蛋白和踝蛋白错位之前。这些肌动蛋白相关蛋白的变化不太可能解释肌动蛋白MFs的初始变化。
