Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK.
School of Life Sciences, University of Lincoln, Brayford Pool, Lincoln, LN6 7DL, UK.
Cell Stress Chaperones. 2018 Jul;23(4):609-615. doi: 10.1007/s12192-017-0870-1. Epub 2017 Dec 29.
A dedicated UNC45, Cro1, She4 (UCS) domain-containing protein assists in the Hsp90-mediated folding of the myosin head. Only weak sequence conservation exists between the single UCS protein of simple eukaryotes (She4 in budding yeast) and the two UCS proteins of higher organisms (the general cell and striated muscle UNC45s; UNC45-GC and UNC45-SM, respectively). In vertebrates, UNC45-GC facilitates cytoskeletal functions, whereas the 55% identical UNC45-SM assists assembly of the contractile apparatus of cardiac and skeletal muscles. A Saccharomyces cerevisiae she4Δ mutant, totally lacking any UCS protein, was engineered to express as its sole Hsp90 either the Hsp90α or the Hsp90β isoforms of human cytosolic Hsp90. A transient induction of the human UNC45-GC, but not UNC45-SM, could rescue the defective endocytosis in these she4Δ cells at 39 °C, irrespective of whether they possessed Hsp90α or Hsp90β. UNC45-GC-mediated rescue of the localisation of a Myo5-green fluorescent protein (GFP) fusion to cortical patches at 39 °C was more efficient in the yeast containing Hsp90α, though this may relate to more efficient functioning of Hsp90α as compared to Hsp90β in these strains. Furthermore, inducible expression of UNC45-GC, but not UNC45-SM, could partially rescue survival at a more extreme temperature (45 °C) that normally causes she4Δ mutant yeast cells to lyse. The results indicate that UCS protein function has been most conserved-yeast to man-in the UNC45-GC, not UNC45-SM. This may reflect UNC45-GC being the vertebrate UCS protein that assists formation of the actomyosin complexes needed for cytokinesis, cell morphological change, and organelle trafficking-events also facilitated by the myosins in yeast.
一个专门的 UNC45、Cro1、She4（UCS）结构域包含蛋白有助于 HSP90 介导的肌球蛋白头部折叠。在简单真核生物的单个 UCS 蛋白（芽殖酵母中的 She4）和高等生物的两个 UCS 蛋白（一般细胞和横纹肌 UNC45；UNC45-GC 和 UNC45-SM，分别）之间，只有弱的序列保守性存在。在脊椎动物中，UNC45-GC 促进细胞骨架功能，而 55%相同的 UNC45-SM 有助于心脏和骨骼肌收缩装置的组装。酵母 cerevisiae she4Δ 突变体完全缺乏任何 UCS 蛋白，被设计为仅表达其作为唯一的 HSP90 是人类细胞质 HSP90 的 HSP90α 或 HSP90β 同工型。在 39°C 时，这些 she4Δ 细胞中的人 UNC45-GC 而不是 UNC45-SM 的瞬时诱导可以挽救其缺陷的胞吞作用，无论它们是否含有 HSP90α 或 HSP90β。UNC45-GC 介导的 Myo5-绿色荧光蛋白（GFP）融合蛋白在 39°C 时向皮质斑的定位的挽救作用在含有 HSP90α 的酵母中更有效，尽管这可能与这些菌株中 HSP90α 相对于 HSP90β 的更有效功能有关。此外，诱导表达 UNC45-GC，但不是 UNC45-SM，在更极端的温度（45°C）下可以部分挽救生存，正常情况下 she4Δ 突变体酵母细胞会裂解。结果表明，UCS 蛋白功能在 UNC45-GC 中而不是 UNC45-SM 中在酵母到人中得到了最保守的保存。这可能反映了 UNC45-GC 是脊椎动物 UCS 蛋白，有助于形成有丝分裂、细胞形态变化和细胞器运输所必需的肌球蛋白复合物，这些复合物在酵母中也被肌球蛋白促进。
