IRE1α knockdown rescues tunicamycin-induced developmental defects and apoptosis in Xenopus laevis.

Li Yuan,Xinxin Li,Chenyang Yin,Xinru Wang,Jiaojiao Feng,Jin Yu

doi:10.7555/jbr.28.20120075

Abstract

Inositol requiring enzyme-1 (IRE1) is highly conserved from yeasts to humans. Upon endoplasmic reticulum (ER) stress, IRE1 activates X-box-binding protein 1 (XBP1) by unconventional splicing of XBP1 mRNA, which activates unfolded protein response (UPR) to restore ER homeostasis. In mice, IRE1α plays an essential role in extraembryonic tissues. However, its precise action during the early stage of development is unknown. In this study, the gain and loss-of-function analyses were used to investigate the function of Xenopus IRE1α (xIRE1α). The effects of xIRE1α during embryo development were detected with RT-PCR and whole mount in situ hybridization. ER stress was induced by tunicamycin. The apoptotic cells were measured by TUNNEL assays. Although both gain and loss of xIRE1α function had no significant effect on Xenopus embryogenesis, knockdown of xIRE1α could rescue tunicamycin-induced developmental defects and apoptosis. The finding indicates that xIRE1α is not required for embryogenesis but is required for tunicamycin-induced developmental defects and apoptosis in Xenopus laevis.

Highlights

The endoplasmic reticulum (ER) plays an important role in the synthesis and modification of secretary and membrane proteins in all eukaryotic cells
To elucidate the function of Xenopus IRE1a (xIRE1a) during early embryonic development, the role of xIRE1a was focused on germ layer formation by gain of function (GOF) and loss of function (LOF) experiments
These results show that xIRE1a is not required for development of X. laevis at early stage

Summary

Introduction

The endoplasmic reticulum (ER) plays an important role in the synthesis and modification of secretary and membrane proteins in all eukaryotic cells. A series of adaptive responses, called the unfolded protein response (UPR), can up-regulate the transcription of various genes to increase the activity of protein-folding and protein-degradation for maintaining ER homeostasis. The UPR is transduced through three forms of ERresident transmembrane sensors: IRE1, PKR-like ER Kinase (PERK), and activating transcription factor 6 (ATF6). IRE1 is an ER-located type I transmembrane protein with a kinase domain and RNase domain in the cytosolic region. It plays a central role in the ER stress response. The specific activity of the endoribonuclease is responsible for the unconventional cytosolic splicing of HAC1 in yeast or excision of the 26-nucleotide intron of the X-box-

Methods

Results

Conclusion