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Multiple dynamin family members collaborate to drive mitochondrial division.

ABSTRACT: Mitochondria cannot be generated de novo; they must grow, replicate their genome, and divide in order to be inherited by each daughter cell during mitosis. Mitochondrial division is a structural challenge that requires the substantial remodelling of membrane morphology. Although division factors differ across organisms, the need for multiple constriction steps and a dynamin-related protein (Drp1, Dnm1 in yeast) has been conserved. In mammalian cells, mitochondrial division has been shown to proceed with at least two sequential constriction steps: the endoplasmic reticulum and actin must first collaborate to generate constrictions suitable for Drp1 assembly on the mitochondrial outer membrane; Drp1 then further constricts membranes until mitochondrial fission occurs. In vitro experiments, however, indicate that Drp1 does not have the dynamic range to complete membrane fission. In contrast to Drp1, the neuron-specific classical dynamin dynamin-1 (Dyn1) has been shown to assemble on narrower lipid profiles and facilitate spontaneous membrane fission upon GTP hydrolysis. Here we report that the ubiquitously expressed classical dynamin-2 (Dyn2) is a fundamental component of the mitochondrial division machinery. A combination of live-cell and electron microscopy in three different mammalian cell lines reveals that Dyn2 works in concert with Drp1 to orchestrate sequential constriction events that build up to division. Our work underscores the biophysical limitations of Drp1 and positions Dyn2, which has intrinsic membrane fission properties, at the final step of mitochondrial division.

SUBMITTER: Lee JE

PROVIDER: S-EPMC5656044 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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Multiple dynamin family members collaborate to drive mitochondrial division.

Lee Jason E JE Westrate Laura M LM Wu Haoxi H Page Cynthia C Voeltz Gia K GK

Nature 20161031 7631

Mitochondria cannot be generated de novo; they must grow, replicate their genome, and divide in order to be inherited by each daughter cell during mitosis. Mitochondrial division is a structural challenge that requires the substantial remodelling of membrane morphology. Although division factors differ across organisms, the need for multiple constriction steps and a dynamin-related protein (Drp1, Dnm1 in yeast) has been conserved. In mammalian cells, mitochondrial division has been shown to proc ...[more]

PMID: 27798601

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Project description:Caveolae are membrane organelles that play roles in glucose and lipid metabolism and in vascular function. Formation of caveolae requires caveolins and cavins. The make-up of caveolae and their density is considered to reflect cell-specific transcriptional control mechanisms for caveolins and cavins, but knowledge regarding regulation of caveolae genes is incomplete. Myocardin (MYOCD) and its relative MRTF-A (MKL1) are transcriptional coactivators that control genes which promote smooth muscle differentiation. MRTF-A communicates changes in actin polymerization to nuclear gene transcription. Here we tested if myocardin family proteins control biogenesis of caveolae via activation of caveolin and cavin transcription. Using human coronary artery smooth muscle cells we found that jasplakinolide and latrunculin B (LatB), substances that promote and inhibit actin polymerization, increased and decreased protein levels of caveolins and cavins, respectively. The effect of LatB was associated with reduced mRNA levels for these genes and this was replicated by the MRTF inhibitor CCG-1423 which was non-additive with LatB. Overexpression of myocardin and MRTF-A caused 5-10-fold induction of caveolins whereas cavin-1 and cavin-2 were induced 2-3-fold. PACSIN2 also increased, establishing positive regulation of caveolae genes from three families. Full regulation of CAV1 was retained in its proximal promoter. Knock down of the serum response factor (SRF), which mediates many of the effects of myocardin, decreased cavin-1 but increased caveolin-1 and -2 mRNAs. Viral transduction of myocardin increased the density of caveolae 5-fold in vitro. A decrease of CAV1 was observed concomitant with a decrease of the smooth muscle marker calponin in aortic aneurysms from mice (C57Bl/6) infused with angiotensin II. Human expression data disclosed correlations of MYOCD with CAV1 in a majority of human tissues and in the heart, correlation with MKL2 (MRTF-B) was observed. The myocardin family of transcriptional coactivators therefore drives formation of caveolae and this effect is largely independent of SRF.

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Multiple dynamin family members collaborate to drive mitochondrial division.

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Multiple dynamin family members collaborate to drive mitochondrial division.

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