Hirschhorn Tal, Levi-Hofman Michal, Danziger Oded, Smorodinsky Nechama I, Ehrlich Marcelo
Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
Cell Mol Life Sci. 2017 Jul;74(14):2645-2662. doi: 10.1007/s00018-017-2488-y. Epub 2017 Mar 29.
The Type-I bone morphogenetic protein receptors (BMPRs), BMPR1A and BMPR1B, present the highest sequence homology among BMPRs, suggestive of functional similitude. However, sequence elements within their extracellular domain, such as signal sequence or N-glycosylation motifs, may result in differential regulation of biosynthetic processing and trafficking and in alterations to receptor function. We show that (i) BMPR1A and the ubiquitous isoform of BMPR1B differed in mode of translocation into the endoplasmic reticulum; and (ii) BMPR1A was N-glycosylated while BMPR1B was not, resulting in greater efficiency of processing and plasma membrane expression of BMPR1A. We further demonstrated the importance of BMPR1A expression and glycosylation in ES-2 ovarian cancer cells, where (i) CRISPR/Cas9-mediated knockout of BMPR1A abrogated BMP2-induced Smad1/5/8 phosphorylation and reduced proliferation of ES-2 cells and (ii) inhibition of N-glycosylation by site-directed mutagenesis, or by tunicamycin or 2-deoxy-D-glucose treatments, reduced biosynthetic processing and plasma membrane expression of BMPR1A and BMP2-induced Smad1/5/8 phosphorylation.
I型骨形态发生蛋白受体（BMPR），即BMPR1A和BMPR1B，在BMPR中具有最高的序列同源性，这表明它们在功能上具有相似性。然而，其细胞外结构域内的序列元件，如信号序列或N-糖基化基序，可能导致生物合成加工和运输的差异调节以及受体功能的改变。我们发现：（i）BMPR1A和普遍存在的BMPR1B异构体在内质网的转运方式上存在差异；（ii）BMPR1A进行了N-糖基化，而BMPR1B没有，这导致BMPR1A的加工效率和质膜表达更高。我们进一步证明了BMPR1A表达和糖基化在ES-2卵巢癌细胞中的重要性，其中：（i）CRISPR/Cas9介导的BMPR1A基因敲除消除了BMP2诱导的Smad1/5/8磷酸化，并降低了ES-2细胞的增殖；（ii）通过定点诱变、衣霉素或2-脱氧-D-葡萄糖处理抑制N-糖基化，降低了BMPR1A的生物合成加工和质膜表达以及BMP2诱导的Smad1/5/8磷酸化。
