Analysis of splice variants of the human protein disulfide isomerase (P4HB) gene

Abstract

AbstractBackgroundProtein 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 theP4HBgene. While forced changes inP4HBgene expression promote physiological effects, little is known about endogenousP4HBgene regulation and, in particular, gene modulation by alternative splicing. This study addressed theP4HBsplice variant landscape.ResultsTen protein coding sequences (Ensembl) of theP4HBgene originating from alternative splicing were characterized. Structural features suggest that except forP4HB-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 andP4HB-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 wasP4HB-021 in human mammary artery vascular smooth muscle which, together with canonicalP4HBgene, had its expression enhanced by serum starvation.ConclusionsOur study details the splice variant landscape of theP4HBgene, 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.