FIGURE 2.

An illustration of MAMs and mitochondrial dysfunction in ER stress. MAMs are the ER membranes at the MERCs, which form a stable bridge between the ER membrane and the OMM, whose fusion is mediated by Mfn1, Mfn2, and Sig-1R. (A) Mfn2 is involved in alterations of mitochondrial morphology through binding to PERK and inhibiting PERK signaling. (B) As the local expression of chaperone proteins, Sig-1/BiP activates the IRE1/XBP1 signaling pathway via IRE1 dimerization. BI-1 resides on the MAMs and regulates mitochondrial Ca2+ concentration and apoptosis.