Ghosh Arit, Coffin Megan, Diaz Dimitri M, Barndt Sarah, Schulz Vincent, Gallagher Patrick, Lo Su Hao, Fowler Velia M
Department of Biological Sciences, University of Delaware, Newark, DE.
Delaware Biotechnology Institute, UD Flow Cytometry Core, Newark, DE.
bioRxiv. 2024 Dec 17:2024.12.13.628322. doi: 10.1101/2024.12.13.628322.
Mammalian red blood cells are generated via a terminal erythroid differentiation pathway culminating in cell polarization and enucleation. Actin filament polymerization is critical for enucleation, but the molecular regulatory mechanisms remain poorly understood. We utilized publicly available RNA-seq and proteomics datasets to mine for actin-binding proteins and actin-nucleation factors differentially expressed during human erythroid differentiation and discovered that a focal adhesion protein-Tensin-1-dramatically increases in expression late in differentiation. Remarkably, we found that differentiating human CD34+ cells express a novel truncated form of Tensin-1 (eTNS1; M ~125 kDa) missing the N-terminal half of the protein, due to an internal mRNA translation start site resulting in a unique exon 1. eTNS1 localized to the cytoplasm during terminal erythroid differentiation, with no apparent membrane association or focal adhesion formation. Knocking out eTNS1 had no effect on assembly of the spectrin membrane skeleton but led to impaired enucleation and absent or mis-localized actin filament foci in enucleating erythroblasts. We conclude that eTNS1 is a novel regulator of actin filament assembly during human erythroid terminal differentiation required for efficient enucleation.
哺乳动物红细胞通过终末红细胞分化途径生成，最终导致细胞极化和去核。肌动蛋白丝聚合对于去核至关重要，但其分子调控机制仍知之甚少。我们利用公开可用的RNA测序和蛋白质组学数据集，挖掘在人类红细胞分化过程中差异表达的肌动蛋白结合蛋白和肌动蛋白成核因子，发现一种粘着斑蛋白——张力蛋白1——在分化后期表达显著增加。值得注意的是，我们发现分化中的人类CD34+细胞表达一种新型的截短形式的张力蛋白1（eTNS1；分子量约125 kDa），该蛋白缺失了蛋白质的N端一半，这是由于一个内部mRNA翻译起始位点导致了一个独特的外显子1。在终末红细胞分化过程中，eTNS1定位于细胞质，没有明显的膜结合或粘着斑形成。敲除eTNS1对血影蛋白膜骨架的组装没有影响，但导致去核受损，并且在去核的成红细胞中肌动蛋白丝焦点缺失或定位错误。我们得出结论，eTNS1是人类红细胞终末分化过程中肌动蛋白丝组装的新型调节因子，是有效去核所必需的。
