Liu H, Bretscher A
Section of Biochemistry, Cornell University, Ithaca, New York 14853.
J Cell Biol. 1992 Jul;118(2):285-99. doi: 10.1083/jcb.118.2.285.
Disruption of the yeast tropomyosin gene TPM1 results in the apparent loss of actin cables from the cytoskeleton (Liu, H., and A. Bretscher. 1989. Cell. 57:233-242). Here we show that TPM1 disrupted cells grow slowly, show heterogeneity in cell size, have delocalized deposition of chitin, and mate poorly because of defects in both shmooing and cell fusion. The transit time of alpha-factor induced a-agglutinin secretion to the cell surface is longer than in isogenic wild-type strains, and some of the protein is mislocalized. Many of the TPM1-deleted cells contain abundant vesicles, similar in morphology to late secretory vesicles, but without an abnormal accumulation of intermediates in the delivery of either carboxypeptidase Y to the vacuole or invertase to the cell surface. Combinations of the TPM1 disruption with sec13 or sec18 mutations, which affect early steps in the secretory pathway, block vesicle accumulation, while combinations with sec1, sec4 or sec6 mutations, which affect a late step in the secretory pathway, have no effect on the vesicle accumulation. The phenotype of the TPM1 disrupted cells is very similar to that of a conditional mutation in the MYO2 gene, which encodes a myosin-like protein (Johnston, G. C., J. A. Prendergast, and R. A. Singer. 1991. J. Cell Biol. 113:539-551). The myo2-66 conditional mutation shows synthetic lethality with the TPM1 disruption, indicating that the MYO2 and TPM1 gene products may be involved in the same, or parallel function. We conclude that tropomyosin, and by inference actin cables, may facilitate directed vesicular transport of components to the correct location on the cell surface.
酵母原肌球蛋白基因TPM1的破坏导致细胞骨架中肌动蛋白电缆明显缺失（刘，H.，和A.布雷舍尔。1989年。《细胞》。57:233 - 242）。在这里我们表明，TPM1破坏的细胞生长缓慢，细胞大小存在异质性，几丁质沉积位置分散，并且由于在“shmoo”形成和细胞融合方面的缺陷而交配不佳。α因子诱导的a -凝集素分泌到细胞表面的转运时间比同基因野生型菌株更长，并且一些蛋白质定位错误。许多缺失TPM1的细胞含有丰富的囊泡，其形态与晚期分泌囊泡相似，但在将羧肽酶Y转运到液泡或将转化酶转运到细胞表面的过程中，中间体没有异常积累。TPM1破坏与影响分泌途径早期步骤的sec13或sec18突变的组合会阻止囊泡积累，而与影响分泌途径晚期步骤的sec1、sec4或sec6突变的组合对囊泡积累没有影响。TPM1破坏的细胞的表型与MYO2基因的条件突变非常相似，MYO2基因编码一种肌球蛋白样蛋白（约翰斯顿，G.C.，J.A.普伦德加斯特，和R.A.辛格。1991年。《细胞生物学杂志》。113:539 - 551）。myo2 - 66条件突变与TPM1破坏表现出合成致死性，表明MYO2和TPM1基因产物可能参与相同或平行的功能。我们得出结论，原肌球蛋白，以及由此推断的肌动蛋白电缆，可能促进组分向细胞表面正确位置的定向囊泡运输。
