CELL MOTILITY AND CHEMOTAXIS IN DICTYOSTELIUM AMEBAE LACKING MYOSIN HEAVY-CHAIN
CELL MOTILITY AND CHEMOTAXIS IN DICTYOSTELIUM AMEBAE LACKING MYOSIN HEAVY-CHAIN
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DOI：
10.1016/0012-1606(88)90279-5
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发表时间：
1988-07-01
影响因子：
2.7
通讯作者：
SPUDICH, J
中科院分区：
文献类型：
--
作者：
WESSELS, D;SOLL, DR;SPUDICH, J
已经通过肌球蛋白重链基因（HMM细胞中的重肌球蛋白）的截短拷贝的同源重组和通过用编码肌球蛋白重链mRNA的反义RNA的载体（mhcA细胞）转化来工程化网骨藻，使得它们缺乏天然肌球蛋白重链蛋白。在前一种情况下，细胞只合成蛋白质的重肌球蛋白部分，而在后一种情况下，它们合成的蛋白质数量可以忽略不计。令人惊讶的是，证明了两种细胞系都是活的和能动的。为了比较这些细胞与正常细胞的运动性，采用了新开发的计算机辅助动态形态学系统（DMS）。结果表明，平均HMM或mhcA阿米巴移动的易位率不到正常细胞的一半。它比正常细胞更圆，极性更小，并且表现出细胞质膨胀和收缩的速率约为正常细胞的一半。在cAMP的空间梯度中，HMM或mhcA的平均阿米巴表现出+0.10或更小的趋化指数，而正常细胞表现出+0.50的趋化指数。最后，伪足的初始面积、扩张速率和最终面积大约是正常细胞的一半。5个最快的HMM阿米巴（详细分析的35个中）以与正常阿米巴相等的平均易位率移动，并且表现出平均趋化指数为+0.34。此外，在快速HMM细胞的平均细胞质流率是等于平均正常阿米巴。然而，快速HMM变形仍然表现出与整个HMM细胞群所表现出的伪足形成相同的缺陷。这些结果表明，肌球蛋白重链参与伪足形成的“微调”和效率，但不是必需的伪足扩展的基本行为。
Dictyostelium amebae have been engineered by homologous recombination of a truncated copy of the myosin heavy chain gene (heavy meromyosin in (HMM) cells) and by transformation with a vector encoding an antisense RNA to myosin heavy chain mRNA (mhcA cells) so that they lack native myosin heavy chain protein. In the former case, cells synthesize only the heavy meromyosin portion of the protein and in the latter case they synthesize negligible amounts of the protein. Surprisingly, it was demonstrated that both cell lines are viable and motile. In order to compare the motility of these cells with normal cells, the newly developed computer-assisted Dynamic Morphology System (DMS) was employed. The results demonstrate that the average HMM or mhcA ameba moves at a rate of translocation less than half that of normal cells. It is rounder and less polar than a normal cell, and exhibits a rate of cytoplasmic expansion and contraction roughly half that of normal cells. In a spatial gradient of cAMP, the average ameba of HMM or mhcA exhibits a chemotactic index of +0.10 or less, compared to the chemotactic index of +0.50 exhibited by normal cells. Finally, the initial area, rate of expansion, and final area of pseudopods are roughly half that of normal cells. The five fastest HMM amebae (out of 35 analyzed in detail) moved at an average rate of translocation equal to that of normal amebae, and exhibited an average chemotactic index of +0.34. In addition, the average rate of cytoplasmic flow in fast HMM cells was equal to that of the average normal ameba. However, fast HMM amebae still exhibited the same defects in pseudopod formation that were exhibited by the entire HMM cell population. These results suggest that myosin heavy chain is involved in the "fine tuning" and efficiency of pseudopod formation, but is not essential for the basic behavior of pseudopod expansion.