Kajihara Daniela, Hon Chung-Chau, Abdullah Aimi Naim, Wosniak João, Moretti Ana Iochabel S, Poloni Joice F, Bonatto Diego, Hashimoto Kosuke, Carninci Piero, Laurindo Francisco R M
Vascular Biology Laboratory, LIM-64, Heart Institute (InCor), University of Sao Paulo School of Medicine, Av. Eneas Carvalho Aguiar, 44, Annex 2, 9th floor, Sao Paulo, CEP 05403-000, Brazil.
Laboratory for Transcriptome Technology, Division of Genomic Medicine, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan.
BMC Genomics. 2020 Nov 4;21(1):766. doi: 10.1186/s12864-020-07164-y.
Protein Disulfide Isomerases are thiol oxidoreductase chaperones from thioredoxin superfamily with crucial roles in endoplasmic reticulum proteostasis, implicated in many diseases. The family prototype PDIA1 is also involved in vascular redox cell signaling. PDIA1 is coded by the P4HB gene. While forced changes in P4HB gene expression promote physiological effects, little is known about endogenous P4HB gene regulation and, in particular, gene modulation by alternative splicing. This study addressed the P4HB splice variant landscape.
Ten protein coding sequences (Ensembl) of the P4HB gene originating from alternative splicing were characterized. Structural features suggest that except for P4HB-021, other splice variants are unlikely to exert thiol isomerase activity at the endoplasmic reticulum. Extensive analyses using FANTOM5, ENCODE Consortium and GTEx project databases as RNA-seq data sources were performed. These indicated widespread expression but significant variability in the degree of isoform expression among distinct tissues and even among distinct locations of the same cell, e.g., vascular smooth muscle cells from different origins. P4HB-02, P4HB-027 and P4HB-021 were relatively more expressed across each database, the latter particularly in vascular smooth muscle. Expression of such variants was validated by qRT-PCR in some cell types. The most consistently expressed splice variant was P4HB-021 in human mammary artery vascular smooth muscle which, together with canonical P4HB gene, had its expression enhanced by serum starvation.
Our study details the splice variant landscape of the P4HB gene, indicating their potential role to diversify the functional reach of this crucial gene. P4HB-021 splice variant deserves further investigation in vascular smooth muscle cells.
蛋白质二硫键异构酶是硫氧还蛋白超家族的硫醇氧化还原酶伴侣，在内质网蛋白质稳态中起关键作用，与多种疾病相关。该家族原型PDIA1也参与血管氧化还原细胞信号传导。PDIA1由P4HB基因编码。虽然P4HB基因表达的强制改变会促进生理效应，但对内源性P4HB基因调控，尤其是可变剪接对基因的调节知之甚少。本研究探讨了P4HB剪接变体情况。
对源自可变剪接的P4HB基因的10个蛋白质编码序列（Ensembl）进行了表征。结构特征表明，除P4HB-021外，其他剪接变体不太可能在内质网发挥硫醇异构酶活性。使用FANTOM5、ENCODE联盟和GTEx项目数据库作为RNA-seq数据源进行了广泛分析。这些分析表明该基因广泛表达，但在不同组织甚至同一细胞的不同位置（例如不同来源的血管平滑肌细胞）中，异构体表达程度存在显著差异。P4HB-02、P4HB-027和P4HB-021在每个数据库中相对表达较多，后者在血管平滑肌中尤为明显。这些变体的表达在一些细胞类型中通过qRT-PCR得到验证。在人乳动脉血管平滑肌中最持续表达的剪接变体是P4HB-021，其与典型P4HB基因一起，在血清饥饿时表达增强。
我们的研究详细描述了P4HB基因的剪接变体情况，表明它们可能在拓展这个关键基因的功能方面发挥作用。P4HB-021剪接变体值得在血管平滑肌细胞中进一步研究。
