Developmental and Tumor Angiogenesis Requires the Mitochondria-Shaping Protein Opa1

While endothelial cell (EC) function is influenced by mitochondrial metabolism, the role of mitochondrial dynamics in angiogenesis, the formation of new blood vessels from existing vasculature, is unknown. Here we show that the inner mitochondrial membrane mitochondrial fusion protein optic atrophy 1 (OPA1) is required for angiogenesis. In response to angiogenic stimuli, OPA1 levels rapidly increase to limit nuclear factor kappa-light-chain-enhancer of activated B cell (NFκB) signaling, ultimately allowing angiogenic genes expression and angiogenesis. Endothelial Opa1 is indeed required in an NFκB-dependent pathway essential for developmental and tumor angiogenesis, impacting tumor growth and metastatization. A first-in-class small molecule-specific OPA1 inhibitor confirms that EC Opa1 can be pharmacologically targeted to curtail tumor growth. Our data identify Opa1 as a crucial component of physiological and tumor angiogenesis

The role of mitochondrial fission factor Drp1 in angiogenesis

Because of the mostly glycolytic nature of endothelial cell metabolism, the role of mitochondria and mitochondrial shape in angiogenesis, the new blood vessel formation from existing vasculature, has not been studied. Here we show that the mitochondrial fission factor Dynamin related protein 1 (Drp1) unexpectedly limits endosomal VEGFR2 signaling and hence angiogenesis. Drp1 levels were reduced when Human Umbilical Vein Endothelial Cells (HUVECs) were activated, and angiogenesis was accordingly stimulated in HUVECs where DRP1 was silenced. In vivo, constitutive and inducible Drp1 ablation in endothelial cells increased early stage postnatal retina vascular sprouting. Mechanistically, upon VEGF stimulation Drp1 interacted with the internalized VEGFR2 and its early endosome partner Rab5 at the endosomal VEGFR2 signaling platform. Drp1 deletion unleashed VEGFR2 activation and its downstream signaling, indicating that the VEGFR2-Rab5-Drp1 interaction limits VEGFR2 mediated angiogenesis. Our data reveal an unexpected extramitochondrial function of Drp1 in endothelial cells, where it localizes also at the endosomes to constrain the endosomal VEGFR2 signaling platform.A causa della natura prevalentemente glicolitica del metabolismo delle cellule endoteliali, il ruolo e la morfologia dei mitocondri nell'angiogenesi, ovvero il processo in cui avviene la formazione di nuovi vasi sanguigni a partire da vasi preesistenti, non è stato studiato. In questa tesi viene mostrato che il fattore di fissione mitocondriale Dynamin related protein 1 (Drp1) limita inaspettatamente la via di segnalazione di VEGFR2 endosomiale e quindi l'angiogenesi. È stato osservato che i livelli di Drp1 sono ridotti nelle cellule endoteliali attivate di vena ombelicale umana (HUVEC); quindi per comprendere il ruolo di Drp1, è stato stimolato il processo di angiogenesi in HUVEC in cui è stato effettuato il silenziamento genico di DRP1. In vivo, la rimozione costitutiva e inducibile di Drp1 nelle cellule endoteliali ha aumentato la vascolarizzazione nella retina durante i primi stadi della fase postnatale. Il meccanismo molecolare proposto prevede che in seguito alla stimolazione di Drp1 da parte di VEGF, esso interagisca con VEGFR2 internalizzato nell’endosoma e con Rab5, GTPasi tipica degli endosomi precoci. La delezione di Drp1 scatena invece l'attivazione di VEGFR2 e la sua via di segnalazione a valle, indicando che l'interazione di VEGFR2-Rab5-Drp1 limita l'angiogenesi mediata da VEGFR2. I dati raccolti rivelano dunque un'inaspettata funzione extramitocondriale di Drp1 nelle cellule endoteliali, in cui si localizza in corrispondenza degli endosomi per limitare la via di segnalazione endosomiale di VEGFR2

The role of mitochondrial fission factor Drp1 in angiogenesis

Because of the mostly glycolytic nature of endothelial cell metabolism, the role of mitochondria and mitochondrial shape in angiogenesis, the new blood vessel formation from existing vasculature, has not been studied. Here we show that the mitochondrial fission factor Dynamin related protein 1 (Drp1) unexpectedly limits endosomal VEGFR2 signaling and hence angiogenesis. Drp1 levels were reduced when Human Umbilical Vein Endothelial Cells (HUVECs) were activated, and angiogenesis was accordingly stimulated in HUVECs where DRP1 was silenced. In vivo, constitutive and inducible Drp1 ablation in endothelial cells increased early stage postnatal retina vascular sprouting. Mechanistically, upon VEGF stimulation Drp1 interacted with the internalized VEGFR2 and its early endosome partner Rab5 at the endosomal VEGFR2 signaling platform. Drp1 deletion unleashed VEGFR2 activation and its downstream signaling, indicating that the VEGFR2-Rab5-Drp1 interaction limits VEGFR2 mediated angiogenesis. Our data reveal an unexpected extramitochondrial function of Drp1 in endothelial cells, where it localizes also at the endosomes to constrain the endosomal VEGFR2 signaling platform

Cerebellar Ataxia and Coenzyme Q Deficiency through Loss of Unorthodox Kinase Activity

International audienceThe UbiB protein kinase-like (PKL) family is widespread, comprising one-quarter of microbial PKLs and five human homologs, yet its biochemical activities remain obscure. COQ8A (ADCK3) is a mammalian UbiB protein associated with ubiquinone (CoQ) biosynthesis and an ataxia (ARCA2) through unclear means. We show that mice lacking COQ8A develop a slowly progressive cerebellar ataxia linked to Purkinje cell dysfunction and mild exercise intolerance, recapitulating ARCA2. Interspecies biochemical analyses show that COQ8A and yeast Coq8p specifically stabilize a CoQ biosynthesis complex through unorthodox PKL functions. Although COQ8 was predicted to be a protein kinase, we demonstrate that it lacks canonical protein kinase activity in trans. Instead, COQ8 has ATPase activity and interacts with lipid CoQ intermediates, functions that are likely conserved across all domains of life. Collectively, our results lend insight into the molecular activities of the ancient UbiB family and elucidate the biochemical underpinnings of a human disease