Disulfide isomerase glucose-regulated protein 58 is required for the nuclear localization and degradation of retinoic acid receptor α

Abstract

Retinoic acid receptor a (RARA) is critical for spermatogenesis, as shown by a sterility phenotype observed in Rara knockout mice. RARA is important in both Sertoli and germ cells of the testis. Here, we demonstrate that a disulfide isomerase glucose-regulated protein 58 (GRp58) participates in the nuclear import and degradation of RARA in Sertoli cells. GRp58 interacted with RARA in the presence of all-trans retinoic acid (ATRA) ligand and, as a complex, it was translocated from the cytoplasm to the nucleus and, then with time, GRp58 dissociated from RARA and was found in the cytoplasm. The GRp58 RNAi treatment disrupted ATRA-dependent RARA nuclear localization, indicating the requirement of GRp58 for RARA nuclear localization. Moreover, treatment with sulfhydryl-modifying agents that oxidize SH-groups of cysteine residues to disulfide bonds abolished ATRA-mediated RARA nuclear localization, suggesting that the thiol oxidoreductase activity of GRp58 may be required for RARA nuclear import. Additionally, the proteasome inhibitor treatment resulted in the co-localization of GRp58 and RARA at the endoplasmic reticulum (ER), suggesting that GRp58 may bring RARA to the ER for the ER-associated degradation (ERAD) of RARA before it is de-coupled from RARA for recycling. In this regard, proteasome inhibitor treatment also increased the interaction of RARA with UBE2J2, an ERAD-associated ubiquitin E2 enzyme. Collectively, the results indicate that GRp58 may act as a molecular chaperone that alters the protein conformation of RARA for its delivery to the nucleus and, then with time, accompanies RARA to the ER for RARA ubiquitination and proteasome-mediated ERAD.

ERp57/GRP58: A protein with multiple functions

“…The presence of ERp57 in the cytosol has been pointed out before when the retinoic acid receptor [55] and STAT3 [56] have been mentioned, and is also required for the transit of ERp57 from the cell membrane to the nucleus upon the binding of calcitriol taking place in the cytosol and also on the cytosolic side of the ER membrane. Furthermore, as mentioned before, a complex of ERp57 and NFκB has been detected in the cytosol of leukemic cells [49].…”

“…The fact that the association of ERp57 with the angiotensin receptor is not trivial but is likely to possess functional significance is suggested by its phosphorylation following angiotensin binding, as demonstrated in a more recent paper [54]. A detailed description of ERp57 interaction with the all-trans retinoic acid receptor α has been reported [55]. In the Sertoli cells it has been shown that ERp57 associates with the receptor in the cytosol, presumably together with other proteins, and is required for the transport of the ligand-receptor complex into the nucleus, and subsequently into the ER to submit the receptor to the degradation process known as ERAD.…”

“…Submit the receptor to the degradation process known as ERAD [55] Interaction with STAT3, in mouse embryonic fibroblasts…”

“…Internalization and nuclear import [43-44, 46, 49] Regulation of bone-related gene transcription and mineralization in osteoblast-like MC3T3-E1 cells [45] Interaction with the angiotensin II receptor [50] Interaction with vasopressin receptor [51] Interaction with the all-trans retinoic acid receptor α [55] Interaction with STAT3 in the lipid raft fraction of cell membrane Participation of a signal transduction pathway initiating at the cell surface [57,58] Cytosol Interaction with STAT3 in the cytosol Present in a multiprotein complex [56][57][58]78] Interaction with the all-trans retinoic acid receptor α Transport of the ligand-receptor complex into the nucleus (in the Sertoli cells) [55] Interaction with NFκB in the cytosol of leukemic cells [49] Redox activity; interaction with Maintenance of the reduced state of Ref-1 (complex, shuttles between the cytosol and the nucleus) [13] Interaction with mTOR Assembly and functioning of the multiprotein complex mTORC1; Appears to be at least in part responsible for the redox dependence of mTORC1 activity [64] Nucleus Redox activity; interaction with Ref-…”

Proteomic analysis of ethanol-induced embryotoxicity in cultured post-implantation rat embryos

“…In this context, expression changes in PDIA3 (also known as GRp58 and ERp57) are intriguing because it is an endoplasmic reticulum stress protein with oxidoreductase activity that regulates cellular redox homeostasis (Frickel et al, 2004;Ni and Lee, 2007). PDIA3 is also involved in the nuclear translocation of retinoic acid receptor alpha (Zhu et al, 2010) and its deficiency is embryonic lethal (Coe et al, 2010). The identified proteins with GO terms classified into "death" may be involved in ethanol-induced apoptosis of neuronal cells, which has frequently been observed (Ahlgren et al, 2002;Giles et al, 2008).…”