Poster: Protein Targeting & Vesicular Trafficking
Abs #
1187: Communication between the Endoplasmic Reticulum and the Nucleus
The endoplasmic reticulum (ER) consists of a three-dimensional network in the cell and is connected to the nuclear envelope. Secretory proteins are correctly assembled in the ER and transported to their final destinations via the membrane traffic. The ER also supplies membranes for plasma membrane and vacuole. Stresses that disturb these ER functions induce various genes to maintain homeostasis of the ER. Then, we are investigating expression profile of these genes and structural changes of the ER when cell is treated with various drugs that disturb the ER function. For this experiment, cells of which ER are tagged with GFP were used. Most notable response is the induction of genes encoding ER chaperones such as BiP on the prevention of protein folding. This phenomenon is named as the unfolded protein response (UPR) or the ER stress response. Very unique mechanism of the UPR pathway, namely signal transduction pathway form the ER to the nucleus, has been characterized in yeast and animals. However molecular basis of the UPR in plants is still largely unknown. Since bZIP proteins play important roles in the UPR pathway of yeast and animals, we screened bZIP genes of Arabidopsis and identified a gene that is highly induced in the UPR. Interestingly it seems to encode a bZIP protein with a transmembrane domain. It could be a functional homolog of ATF6 (the most important transcription factor in the mammalian UPR), a bZIP protein localizing to the ER membrane. Since ATF6 becomes a soluble form by proteolysis upon the UPR, we are examining whether similar mechanism could be observed in plants. Further characterization of this bZIP gene will be reported.
