Novel Cis-acting Element GASE Regulates Transcriptional Induction by the Golgi Stress Response

Abstract

ABSTRACT. When increased production of secretory proteins overwhelms the capacity of the endoplasmic reticulum (ER) and the Golgi apparatus, eukaryotic cells expand their capacity to sustain secretory function. The capacity of the ER is enhanced by the mechanism called the ER stress response, but the mechanism regulating Golgi capacity (the Golgi stress response) has remained unclear. Here, we found that transcription of Golgirelated genes, including glycosylation enzymes as well as factors involved in post-Golgi vesicular transport and maintenance of Golgi structure, was upregulated upon treatment with monensin, an ionophore that disrupts the function of acidic organelles, including the Golgi apparatus and lysosomes by neutralizing their lumen. This transcriptional induction was found to be commonly regulated by a novel cis-acting element called the Golgi apparatus stress response element (GASE), whose consensus sequence is ACGTGgc. When the function of the Golgi apparatus was specifically disturbed by overexpression of GCP60, a Golgi-localized protein that binds to giantin, transcription from GASE was significantly induced. These results suggest that mammalian cells have the Golgi stress response, and that GASE regulates transcriptional induction involved in the Golgi stress response.

TFE3, HSP47, and CREB3 Pathways of the Mammalian Golgi Stress Response

“…Thus, upon monensin treatment, the pH of the Golgi becomes neutralized and the activity of Golgi proteins severely reduced, resulting in insufficiency in Golgi functions such as glycosylation and vesicular transport (Golgi stress). Although the lysosome and mitochondrial intermembrane space are also acidic compartments and could be affected by monensin treatment, monensin treatment hardly affected the expression of lysosomal and mitochondrial genes (Oku et al, 2011), probably as a result of differences in lipid content between the Golgi and lysosomal/mitochondrial membrane (Dinter and Berger, 1998). Upon monensin treatment, the Golgi apparatus becomes swollen and remarkably expanded because of the influx of water and/or accumulation of secretory proteins (Dinter and Berger, 1998).…”

“…Upon monensin treatment, the Golgi apparatus becomes swollen and remarkably expanded because of the influx of water and/or accumulation of secretory proteins (Dinter and Berger, 1998). Usually, the Golgi cannot be observed by phase-contrast microscopy, but upon monensin treatment the Golgi swells so that it can be clearly detected (Oku et al, 2011). Nigericin, another ionophore that antiports K + and H + , is also used as a Golgi stress inducer in a working mechanism similar to monensin (Oku et al, 2011).…”

“…Usually, the Golgi cannot be observed by phase-contrast microscopy, but upon monensin treatment the Golgi swells so that it can be clearly detected (Oku et al, 2011). Nigericin, another ionophore that antiports K + and H + , is also used as a Golgi stress inducer in a working mechanism similar to monensin (Oku et al, 2011).…”

“…The third method to activate the TFE3 pathway is ectopic expression of a dominant negative form of GCP60 (GCP60-DN) (Oku et al, 2011;Taniguchi et al, 2015). GCP60 is a Golgi structural protein associated with Giantin, a Golgi integral membrane protein (see below).…”

“…The molecular mechanism of the Golgi stress response has been less analyzed compared with that of the ER stress response, but recent studies revealed an important part of the regulatory mechanism, including the TFE3, HSP47, and CREB3 pathways (Fig. 3) (Miyata et al, 2013;Oku et al, 2011;Reiling et al, 2013;Taniguchi et al, 2015Taniguchi et al, , 2016.…”