Receptor-mediated Drp1 oligomerization on endoplasmic reticulum

Abstract

Drpl is a dynamin GTPase important for mitochondrial and peroxisomal division. Drp1 oligomerization and mitochondrial recruitment are regulated by multiple factors, including interaction with mitochondrial receptors such as Mff, MiD49, MiD51 and Fis. In addition, both endoplasmic reticulum (ER) and actin filaments play positive roles in mitochondrial division, but mechanisms for their roles are poorly defined. Here, we find that a population of Drp1 oligomers is ER-associated in mammalian cells, and is distinct from mitochondrial or peroxisomal Drp1 populations. Sub-populations of Mff and Fis1, which are tail-anchored proteins, also localize to ER. Drp1 oligomers assemble on ER, from which they can transfer to mitochondria. Suppression of Mff or inhibition of actin polymerization through the formin INF2 significantly reduces all Drp1 oligomer populations (mitochondrial, peroxisomal, ER-bound) and mitochondrial division, while Mff targeting to ER has a stimulatory effect on division. Our results suggest that ER can function as a platform for Drp1 oligomerization, and that ER-associated Drp1 contributes to mitochondrial division.SummaryAssembly of the dynamin GTPase Drp1 into constriction-competent oligomers is a key event in mitochondrial division. Here, Ji et al show that Drp1 oligomerization can occur on endoplasmic reticulum through an ER-bound population of the tail-anchored protein Mff.Abbreviations used in this paper: Drp1, dynamin-related protein 1; Fis1, mitochondrial fission 1 protein; INF2, inverted formin 2; KD, siRNA-mediated knock down; KI, CRISPR-mediated knock in; KO, CRISPR-mediated knock out; LatA, Latrunculin A; MDV, mitochondrially-derived vesicle; Mff, mitochondrial fission factor; MiD49 and MiD51, mitochondrial dynamics protein of 49 and 51 kDa; OMM, outer mitochondrial membrane; TA, tail-anchored.

INF2-mediated actin polymerization at the ER stimulates mitochondrial calcium uptake, inner membrane constriction, and division

“…6, D and E ). Because Drp1 can oligomerize on peroxisomes and ER independently of mitochondria ( Ji et al, 2017 ), we also assessed total cellular Drp1 oligomers and found similar ionomycin-induced oligomerization kinetics between control and MCU KD cells ( Fig. 6 F ).…”

“…Because Drp1 is a key mitochondrial division factor, and because we previously showed that ionomycin causes increased Drp1 oligomerization ( Ji et al, 2015 ), we tested the effect of MCU-KD on Drp1 oligomerization. In a CRISPR-derived GFP-Drp1 knock-in cell line ( Ji et al, 2017 ), MCU suppression does not significantly alter ionomycin-induced Drp1 oligomerization on mitochondria ( Fig. 6, D and E ).…”

“…Human osteosarcoma U2OS cells (HTB96; American Type Culture Collection) were grown in DMEM (Invitrogen) supplemented with 10% calf serum (Atlanta Biologicals). The GFP-Drp1 KI U2OS cell line made by CRISPR-Cas9 is described elsewhere ( Ji et al, 2017 ). In brief, we used the GeCKO system (Zhang laboratory, Massachusetts Institute of Technology, Cambridge, MA; http://genome-engineering.org/gecko/ ).…”

Drp1 knockdown induces severe muscle atrophy and remodelling, mitochondrial dysfunction, autophagy impairment and denervation

“…This view is further strengthened by the absence of increase in the expression of the mitochondrial antioxidant enzyme Sod2. Since Drp1 is also known to regulate peroxisomal division (Ji et al 2017), it is possible that oxidative stress might have been caused by Drp1 KD-induced peroxisomal dysfunction. It is also possible that Drp1 KD might have increased the activity of other important sources of ROS, such as the cytosolic NADPH oxidase.…”

Targeted OMA1 therapies for cancer

“…The outer membrane proteins MID51, MID49, MFF and FIS1 can recruit DNM1L to mitochondria-ER contact sites for mitochondrial fission. [40][41][42][43][44] Additionally, fission can be regulated through different posttranslational DNM1L modifications. 45,46 The mitofusins MFN1 and MFN2 are two related mitochondrial outer membrane fusion proteins with slightly different functions and expression patterns.…”