[3P-75] Elucidating mechanisms and pathways by which disulfide-catalysts assist oxidative protein folding in the endoplasmic reticulum
In the mammalian endoplasmic reticulum (ER), to properly guide a disulfide bond formation during client folding, there is a complicated but sophisticated disulfide catalytic network composed of over 20 members of protein disulfide isomerase (PDI) family and several upstream PDI-oxidases. Despite the discovery of these disulfide-catalysts, the following issues remained to be addressed: 1) how and when disulfide bonds are formed in proteins inserted into the ER and 2) how the redox status of the PDI family in the ER is maintained. To develop a disulfide monitoring system, we utilized a semi-permeabilized cell combined with an in vitro translation system. In consequence, we elucidated the mechanistic aspects of co-translational oxidative folding that allow promoting native disulfide formation. We further revealed the molecular mechanism, by which ER oxidoreductin 1α and glutathione peroxidase 7/8 as upstream PDI-oxidases maintains the redox status of PDI family. Thus, these studies provided mechanistic insights into the disulfide catalytic networks in the ER, allowing for the introduction of disulfide bonds into newly-synthesized proteins during client folding.