cells Review Role of Endoplasmic Reticulum Stress Sensor IRE1α in Cellular Physiology, Calcium, ROS Signaling, and Metaflammation Thoufiqul Alam Riaz 1 , Raghu Patil Junjappa 1 , Mallikarjun Handigund 2 , Jannatul Ferdous 3, Hyung-Ryong Kim 4,* and Han-Jung Chae 1,* 1 Department of Pharmacology, School of Medicine, Institute of New Drug Development, Jeonbuk National University, Jeonju 54907, Korea; toufi
[email protected] (T.A.R.);
[email protected] (R.P.J.) 2 Department of Laboratory Medicine, Jeonbuk National University, Medical School, Jeonju 54907, Korea;
[email protected] 3 Department of Radiology and Research Institute of Clinical Medicine of Jeonbuk National University, Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju 54907, Korea;
[email protected] 4 College of Dentistry, Dankook University, Cheonan 31116, Korea * Correspondence:
[email protected] (H.-R.K);
[email protected] (H.-J.C) Received: 9 April 2020; Accepted: 6 May 2020; Published: 8 May 2020 Abstract: Inositol-requiring transmembrane kinase endoribonuclease-1α (IRE1α) is the most prominent and evolutionarily conserved unfolded protein response (UPR) signal transducer during endoplasmic reticulum functional upset (ER stress). A IRE1α signal pathway arbitrates yin and yang of cellular fate in objectionable conditions. It plays several roles in fundamental cellular physiology as well as in several pathological conditions such as diabetes, obesity, inflammation, cancer, neurodegeneration, and in many other diseases. Thus, further understanding of its molecular structure and mechanism of action during different cell insults helps in designing and developing better therapeutic strategies for the above-mentioned chronic diseases. In this review, recent insights into structure and mechanism of activation of IRE1α along with its complex regulating network were discussed in relation to their basic cellular physiological function.