Department of Molecular and Cellular Biology, University of California, Davis, Davis, United States.
Elife. 2021 Apr 16;10:e61069. doi: 10.7554/eLife.61069.
KASH proteins in the outer nuclear membrane comprise the cytoplasmic half of linker of nucleoskeleton and cytoskeleton (LINC) complexes that connect nuclei to the cytoskeleton. ANC-1, an ortholog of Nesprin-1/2, contains actin-binding and KASH domains at opposite ends of a long spectrin-like region. Deletion of either the KASH or calponin homology (CH) domains does not completely disrupt nuclear positioning, suggesting neither KASH nor CH domains are essential. Deletions in the spectrin-like region of ANC-1 led to significant defects, but only recapitulated the null phenotype in combination with mutations in the transmembrane (TM) span. In mutants, the endoplasmic reticulum ER, mitochondria, and lipid droplets were unanchored, moving throughout the cytoplasm. The data presented here support a cytoplasmic integrity model where ANC-1 localizes to the ER membrane and extends into the cytoplasm to position nuclei, ER, mitochondria, and other organelles in place.
核膜外的 KASH 蛋白构成了核骨架和细胞骨架(LINC)连接复合物的细胞质部分,将细胞核与细胞骨架连接起来。ANC-1 是 Nesprin-1/2 的同源物,在长的类似于血影蛋白的区域的两端包含肌动蛋白结合和 KASH 结构域。KASH 或钙调蛋白同源(CH)结构域的缺失并不完全破坏核定位,这表明 KASH 或 CH 结构域都不是必需的。ANC-1 中类似于血影蛋白的区域的缺失导致了明显的缺陷,但只有与跨膜(TM)跨度的突变相结合时,才会重现完全缺失表型。在 突变体中,内质网(ER)、线粒体和脂滴没有被固定,而是在细胞质中移动。这里呈现的数据支持细胞质完整性模型,其中 ANC-1 定位于内质网膜并延伸到细胞质中,以将细胞核、内质网、线粒体和其他细胞器定位在适当的位置。