Mitochondrial Cristae: Where Beauty Meets Functionality Sara Cogliati, Jose A. Enriquez, Luca Scorrano  Trends in Biochemical Sciences  Volume 41, Issue 3, Pages 261-273 (March 2016) DOI: 10.1016/j.tibs.2016.01.001 Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 1 The Supercomplexes Are Disorganized when Cristae Are Unfolded. Schematic representation of the oxidative phosphorylation (OXPHOS) system in a folded crista (A). The different complexes are assembled in different supercomplexes of very dynamic compositions along the cristae membrane. The dimers of ATP synthase are organized in long rows on the edge of the cristae and cytochrome c is maintained inside the cristae. In this situation, the electron transport chain works efficiently (represented by short arrows between the complexes) and the proton gradient accumulates at the edge of the cristae, where the ATP synthase can use it. Upon perturbation of cristae structure (B), supercomplexes and dimers of ATP synthase disassemble and cytochrome c is mobilized. As a result, the electron transport chain is less efficient (longer arrows) and, thus, the mitochondrial respiratory performance decreases. (The amount of H+, and the localization and amount of complexes and supercomplexes are only representative and do not correspond to the real stoichiometry.) Trends in Biochemical Sciences 2016 41, 261-273DOI: (10.1016/j.tibs.2016.01.001) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 2 Proteins Involved in Mitochondrial Ultrastructural Organization. Correct mitochondrial shape is necessary for the proper assembly and stabilization of supercomplexes (SCs). Many proteins have been described to be involved in the maintenance of the cristae shape. Thus, they are also important for the structure of SCs. Here, we provide a schematic diagram of a portion of the outer mitochondrial membrane (OMM), inner mitochondrial membrane (IMM), and cristae summarizing the proteins involved in the architecture of the cristae. In the OMM, sorting and assembly machinery (SAM) complex, interacts (segmented arrows) with the mitochondrial contact site and cristae-organizing system (MICOS) complex, which is located in the IMM close to the cristae junctions. OPA1 keeps the cristae junctions closed and is regulated by Gαq/11 (dotted arrows), PARL, ROMO1, and by the mitochondrial matrix ATPase proteases (m-AAA), which are controlled by the prohibitin–stomatin-like protein 2 (PHB–SLP2) complex assembled into cardiolipin (red cylinder)-enriched domains. If all these proteins are functional and properly localized, the cristae are folded and the respiratory chain complexes are dynamically organized in SCs. Trends in Biochemical Sciences 2016 41, 261-273DOI: (10.1016/j.tibs.2016.01.001) Copyright © 2016 Elsevier Ltd Terms and Conditions