bims-midbra 2022-04-03 papers

Issue of 2022–04–03
four papers selected by
Ana Paula Mendonça, University of Padova

Autophagy. 2022 Mar 29. 1-3

Proteomic profiling shows mitochondrial nucleoids are autophagy cargo in neurons: implications for neuron maintenance and neurodegenerative disease.

Juliet Goldsmith, Erika L F Holzbaur.

Neurons depend on macroautophagy/autophagy to maintain cellular homeostasis, and loss of autophagy leads to neurodegeneration. To better understand the role of basal autophagy in neurons, we enriched autophagic vesicles from healthy adult mouse brain and performed mass spectrometry to identify cargos cleared by autophagy. We found that synaptic and mitochondrial proteins comprise nearly half of the unique AV cargos identified in brain. Similarly, synaptic and mitochondrial proteins are major cargos for basal autophagy in neurons. Strikingly, we noted a specific enrichment of mitochondrial nucleoids within neuronal autophagosomes, which occurs through a mechanism distinct from damage-associated mitophagy. Here, we discuss the implications of these findings for our understanding of homeostatic mechanisms in neurons and how the age-dependent decline of autophagy in neurons may contribute to the onset or progression of neurodegenerative disease.

Keywords: DNM1L; SYN1; TFAM; macroautophagy; mitochondria; mitochondrial division; mitochondrial nucleoids; mitophagy; neurodegeneration; neuronal homeostasis

DOI: https://doi.org/10.1080/15548627.2022.2056865

Int Ophthalmol. 2022 Mar 31.

Mesenchymal stem cells (MSCs) in Leber's hereditary optic neuropathy (LHON): a potential therapeutic approach for future.

Mohana Devi Subramaniam, Ruth Bright Chirayath, Mahalaxmi Iyer, Aswathy P Nair, Balachandar Vellingiri.

BACKGROUND: Optic neuropathy has become a new typical syndromic multi-system disease that leads to optic atrophy. This review discusses potential treatments and advances of Leber's hereditary optic neuropathy (LHON), a sporadic genetic disorder. LHON is caused due to slight mutations in mitochondria leading to mitochondrial dysfunction, causing vision loss. There are no current significant treatments that have been proven to work for LHON.
METHODS: However, extensive review was carried out on capable studies that have shown potential treatment sensory systems and are being evaluated currently. Some of these studies are in clinical trials, whereas other ones are still being planned. Here, we focus more on treatment based on mesenchymal stem cells-mediated mitochondrial transfer via various techniques. We discuss different mitochondrial transfer modes and possible ways to understand the mitochondria transfer technique's phenotypic characteristics.
CONCLUSION: It is clearly understood that transfer of healthy mitochondria from MSC to target cell would regulate the range of reactive oxygen species and ATP'S, which are majorly responsible for mutation upon irregulating. Therefore, mitochondrial transfer is suggested and discussed in this review with various aspects. The graphical abstract represents different means of mitochondrial transport like (a) Tunnelling nanotubules, (b) Extracellular vesicles, (c) Cell fusion and (d) Gap junctions. In (a) Tunnelling nanotubules, the signalling pathways TNF- α/TNF αip2 and NFkB/TNF αep2 are responsible for forming tunnels. Also, Miro protein acts as cargo for the transport of mitochondria with myosin's help in the presence of RhoGTPases [35]. In (b) Extracellular vesicles, the RhoA ARF6 contributes to Actin/Cytoskeletal rearrangement leading to the shedding of microvesicles. Coming to (c) Cell fusion when there is a high amount of ATP, the cells tend to fuse when in close proximity leading to the transfer of mitochondria via EFF-1/HAP2 [48]. In (d) Gap Junctions, Connexin43 is responsible for the intracellular channel in the presence of more ATP [86].

Keywords: Gene therapy; Leber’s hereditary optic neuropathy; Mesenchymal stem cells; Micro-vesicles-mediated transfer; Mitochondrial transfer; Tunnelling nanotubes

DOI: https://doi.org/10.1007/s10792-022-02267-9

Front Mol Biosci. 2022 ;9 835302

A Nanobody-Based Toolset to Monitor and Modify the Mitochondrial GTPase Miro1.

Funmilayo O Fagbadebo, Philipp D Kaiser, Katharina Zittlau, Natascha Bartlick, Teresa R Wagner, Theresa Froehlich, Grace Jarjour, Stefan Nueske, Armin Scholz, Bjoern Traenkle, Boris Macek, Ulrich Rothbauer.

The mitochondrial outer membrane (MOM)-anchored GTPase Miro1, is a central player in mitochondrial transport and homeostasis. The dysregulation of Miro1 in amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD) suggests that Miro1 may be a potential biomarker or drug target in neuronal disorders. However, the molecular functionality of Miro1 under (patho-) physiological conditions is poorly known. For a more comprehensive understanding of the molecular functions of Miro1, we have developed Miro1-specific nanobodies (Nbs) as novel research tools. We identified seven Nbs that bind either the N- or C-terminal GTPase domain of Miro1 and demonstrate their application as research tools for proteomic and imaging approaches. To visualize the dynamics of Miro1 in real time, we selected intracellularly functional Nbs, which we reformatted into chromobodies (Cbs) for time-lapse imaging of Miro1. By genetic fusion to an Fbox domain, these Nbs were further converted into Miro1-specific degrons and applied for targeted degradation of Miro1 in live cells. In summary, this study presents a collection of novel Nbs that serve as a toolkit for advanced biochemical and intracellular studies and modulations of Miro1, thereby contributing to the understanding of the functional role of Miro1 in disease-derived model systems.

Keywords: Miro1; degron; imaging; nanobodies; proteomics

DOI: https://doi.org/10.3389/fmolb.2022.835302

Exp Neurol. 2022 Mar 24. pii: S0014-4886(22)00080-2. [Epub ahead of print] 114055

Metformin attenuates early brain injury after subarachnoid hemorrhage in rats via AMPK-dependent mitophagy.

Yongzhi Zhang, Tongyu Zhang, Yuchen Li, Yu Guo, Binbing Liu, Yang Tian, Pei Wu, Huaizhang Shi.

Metformin is the most widely used drug to treat type 2 diabetes and its mitochondrial activity is through activation of adenosine monophosphate-activated protein kinase (AMPK). AMPK plays a dual regulatory role in mito-morphosis, controlling the phosphorylation and activation of dynamin-related protein 1 (DRP1) and mitofusin 2 (MFN2). The aim of this study was to investigate whether metformin could reduce early brain injury (EBI) after subarachnoid hemorrhage (SAH) by activating mitophagy and improving mitochondrial morphology through AMPK. This study used 308 male Sprague-Dawley rats. First, different metformin doses were injected intraperitoneally 30 min post-SAH. The dose that did not significantly alter blood glucose in the rats was selected for subsequent experiments. Before or after sacrificing rats, neurological function, brain water content, and blood-brain barrier (BBB) permeability were measured in each group. Transmission electron microscopy was used to observe the level of mitophagy and mito-morphology in each group. The expression of mitophagic and apoptotic proteins were investigated by immunofluorescence and western blot. Metformin at 20 mg/kg improved neurological function and attenuated brain edema and the disruption of BBB permeability 24 h after SAH. Metformin treatment after SAH promoted mitophagy in an AMPK-dependent manner. In addition to the effects on mitophagy, we also found that metformin alleviated oxidative stress and apoptosis after SAH in an AMPK-dependent manner. Lastly, metformin restored homeostasis between mitochondrial fusion and fission. Metformin attenuated EBI after SAH in rats through AMPK-dependent signaling. These protective effects might be achieved by regulating mitochondrial morphology and promoting mitophagy.

Keywords: Early brain injury; Metformin; Mitophagy; Subarachnoid hemorrhage

DOI: https://doi.org/10.1016/j.expneurol.2022.114055