Program in Molecular, Cellular, Developmental Biology, and Genetics, and.
Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455.
Mol Biol Cell. 2022 Aug 1;33(9):ar77. doi: 10.1091/mbc.E22-02-0054. Epub 2022 May 20.
Cytoplasmic β- and γ-actin proteins are 99% identical but support unique organismal functions. The cytoplasmic actin nucleotide sequences and , respectively, are more divergent but still 89% similar. mice are embryonic lethal and cells fail to proliferate, but editing the gene to express γ-actin () resulted in none of the overt phenotypes of the knockout revealing protein-independent functions for . To determine if has a protein-independent function, we crossed and mice to generate the bG/0 line, where the only cytoplasmic actin expressed is γ-actin from . The bG/0 mice were viable but showed a survival defect despite expressing γ-actin protein at levels no different from bG/gG with normal survival. A unique myopathy phenotype was also observed in bG/0 mice. We conclude that impaired survival and myopathy in bG/0 mice are due to loss of nucleotide-dependent function(s). On the other hand, the bG/0 genotype rescued functions impaired by , including cell proliferation and auditory function, suggesting a role for γ-actin protein in both fibroblasts and hearing. Together, these results identify nucleotide-dependent functions for while implicating γ-actin protein in more cell-/tissue-specific functions.
细胞质β-和γ-肌动蛋白蛋白在 99%的序列上是相同的，但支持独特的生物体功能。细胞质肌动蛋白的核苷酸序列和分别更具差异性，但仍有 89%的相似性。缺失小鼠胚胎致死，细胞无法增殖，但编辑基因表达 γ-肌动蛋白（）则没有表现出敲除的明显表型，揭示了肌动蛋白的蛋白非依赖性功能。为了确定肌动蛋白是否具有蛋白非依赖性功能，我们将和小鼠杂交，生成 bG/0 系，其中唯一表达的细胞质肌动蛋白是来自的 γ-肌动蛋白。bG/0 小鼠是有活力的，但尽管表达 γ-肌动蛋白蛋白的水平与正常存活的 bG/gG 没有不同，但仍表现出生存缺陷。在 bG/0 小鼠中还观察到一种独特的肌肉病表型。我们得出结论，bG/0 小鼠的生存缺陷和肌肉病是由于丧失了肌动蛋白核苷酸依赖性功能。另一方面，bG/0 基因型挽救了由缺失引起的功能障碍，包括细胞增殖和听觉功能，这表明 γ-肌动蛋白蛋白在成纤维细胞和听力中都具有作用。总之，这些结果确定了肌动蛋白核苷酸依赖性功能，同时暗示了 γ-肌动蛋白蛋白在更具细胞/组织特异性的功能中发挥作用。
