Figure 8. Putative model for how mitochondrial Spire1C and ER-anchored INF2 could mediate mitochondrial constriction via actin filament assembly.
(A) Spire1C:actin complexes on mitochondria associate with INF2 on the ER. Actin filaments nucleated by Spire1C are elongated by the actin polymerization activity of INF2. The actin filament elongation activity exerts pressure on the mitochondrial outer membrane, thereby driving constriction of the latter. Tethering complexes may play a role in maintaining association between ER and mitochondrial membranes. Myosin-II dimers and the related contractile actin ring, which may also be involved in mitochondrial constriction, are not shown for simplicity. (B) Computational results showing mitochondrial shapes resulting from deformation by constricting pressure P developed by the actin polymerization and/or actin contractile based mechanisms (see also Figure 8—figure supplement 1, Figure 8—source data 1, and ‘Materials and methods’ for more information). The mitochondrial constriction site was modeled as a tubular membrane of about 680 nm length and with initial radius R = 230 nm. The dark blue strip in the middle represents the 50 nm wide zone of the pressure application. The images correspond to 3° of the mitochondria constriction characterized by cross-sectional radii r in the narrowest place of 145 nm, 110 nm and 65 nm. The corresponding values of the pressure P, the required numbers of the polymerizing actin filaments, Nf, and the required tensions in the actin contractile ring, γm, are presented in Figure 8—figure supplement 1 and Figure 8—source data 1.
DOI: http://dx.doi.org/10.7554/eLife.08828.019
Figure 8—figure supplement 1. Computational results of simulations of mitochondrial constriction mediated by actin polymerization and actin constriction mechanisms.
