Although not directly shown in C. elegans, BiP/GRP78 (HSP-3 or HSP-4 in C. elegans) has been shown to bind to IRE-1 in its monomeric state in other organisms. Unfolded proteins are thought to compete with IRE-1 for binding to BiP/GRP78 such that an increased load of unfolded proteins would cause dissociation of BiP/GRP78 from IRE-1, thereby allowing IRE-1 dimerization and subsequent activation of XBP-1.