Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
Dev Cell. 2013 Aug 12;26(3):315-23. doi: 10.1016/j.devcel.2013.06.016. Epub 2013 Aug 1.
Dynamic interactions between membrane-bound organelles and the microtubule cytoskeleton are crucial to establish, maintain, and remodel the internal organization of cells throughout the cell cycle. However, the molecular nature of these interactions remains poorly understood. We performed a biochemical screen for microtubule-membrane linkers and identified REEP4, a previously uncharacterized endoplasmic reticulum (ER) protein. Depletion of REEP4 and the closely related REEP3 from HeLa cells causes defects in cell division and a proliferation of intranuclear membranes derived from the nuclear envelope. This phenotype originates in mitosis, when ER membranes accumulate on metaphase chromosomes. Microtubule binding and mitotic ER clearance from chromosomes both depend on a short, positively charged amino acid sequence connecting the two hydrophobic domains of REEP4. Our results show that REEP3/4 function redundantly to clear the ER from metaphase chromatin, thereby ensuring correct progression through mitosis and proper nuclear envelope architecture.
膜结合细胞器与微管细胞骨架之间的动态相互作用对于在整个细胞周期中建立、维持和重塑细胞的内部组织至关重要。然而，这些相互作用的分子性质仍知之甚少。我们进行了一个生化筛选，以寻找微管-膜连接蛋白，鉴定出REEP4，这是一种以前未被描述的内质网（ER）蛋白。从 HeLa 细胞中耗尽 REEP4 和密切相关的 REEP3 会导致细胞分裂缺陷，并导致源自核膜的核内膜增殖。这种表型起源于有丝分裂，此时内质网（ER）膜在中期染色体上积累。微管结合和有丝分裂期间 ER 从染色体上的清除都依赖于 REEP4 的两个疏水区之间连接的一个短的、带正电荷的氨基酸序列。我们的结果表明，REEP3/4 冗余地发挥作用，从中期染色质中清除 ER，从而确保有丝分裂的正确进行和核膜结构的正常。
