bims-mecosi 2022-01-23 papers

Issue of 2022‒01‒23
four papers selected by
Verena Kohler

Int J Mol Sci. 2022 Jan 11. pii: 780. [Epub ahead of print]23(2):

Impact of ER Stress and ER-Mitochondrial Crosstalk in Huntington's Disease.

Shuvadeep Maity, Pragya Komal, Vaishali Kumar, Anshika Saxena, Ayesha Tungekar, Vaani Chandrasekar.

Accumulation of misfolded proteins is a common phenomenon of several neurodegenerative diseases. The misfolding of proteins due to abnormal polyglutamine (PolyQ) expansions are linked to the development of PolyQ diseases including Huntington's disease (HD). Though the genetic basis of PolyQ repeats in HD remains prominent, the primary molecular basis mediated by PolyQ toxicity remains elusive. Accumulation of misfolded proteins in the ER or disruption of ER homeostasis causes ER stress and activates an evolutionarily conserved pathway called Unfolded protein response (UPR). Protein homeostasis disruption at organelle level involving UPR or ER stress response pathways are found to be linked to HD. Due to dynamic intricate connections between ER and mitochondria, proteins at ER-mitochondria contact sites (mitochondria associated ER membranes or MAMs) play a significant role in HD development. The current review aims at highlighting the most updated information about different UPR pathways and their involvement in HD disease progression. Moreover, the role of MAMs in HD progression has also been discussed. In the end, the review has focused on the therapeutic interventions responsible for ameliorating diseased states via modulating either ER stress response proteins or modulating the expression of ER-mitochondrial contact proteins.

Keywords: ER; ER stress; Huntington’s disease (HD); mitochondria; mitochondria associated ER membranes (MAM)

DOI: https://doi.org/10.3390/ijms23020780

Antioxidants (Basel). 2022 Jan 15. pii: 165. [Epub ahead of print]11(1):

Therapeutic Strategies Targeting Mitochondrial Calcium Signaling: A New Hope for Neurological Diseases?

Laura R Rodríguez, Tamara Lapeña-Luzón, Noelia Benetó, Vicent Beltran-Beltran, Federico V Pallardó, Pilar Gonzalez-Cabo, Juan Antonio Navarro.

Calcium (Ca2+) is a versatile secondary messenger involved in the regulation of a plethora of different signaling pathways for cell maintenance. Specifically, intracellular Ca2+ homeostasis is mainly regulated by the endoplasmic reticulum and the mitochondria, whose Ca2+ exchange is mediated by appositions, termed endoplasmic reticulum-mitochondria-associated membranes (MAMs), formed by proteins resident in both compartments. These tethers are essential to manage the mitochondrial Ca2+ influx that regulates the mitochondrial function of bioenergetics, mitochondrial dynamics, cell death, and oxidative stress. However, alterations of these pathways lead to the development of multiple human diseases, including neurological disorders, such as amyotrophic lateral sclerosis, Friedreich's ataxia, and Charcot-Marie-Tooth. A common hallmark in these disorders is mitochondrial dysfunction, associated with abnormal mitochondrial Ca2+ handling that contributes to neurodegeneration. In this work, we highlight the importance of Ca2+ signaling in mitochondria and how the mechanism of communication in MAMs is pivotal for mitochondrial maintenance and cell homeostasis. Lately, we outstand potential targets located in MAMs by addressing different therapeutic strategies focused on restoring mitochondrial Ca2+ uptake as an emergent approach for neurological diseases.

Keywords: Charcot–Marie–Tooth; Friedreich’s ataxia; amyotrophic lateral sclerosis; calcium; endoplasmic reticulum; mitochondria; mitochondrial calcium uniporter; neurological; sigma-1 receptor

DOI: https://doi.org/10.3390/antiox11010165

Front Cell Dev Biol. 2021 ;9 774108

OPA1 Modulates Mitochondrial Ca2+ Uptake Through ER-Mitochondria Coupling.

Benjamín Cartes-Saavedra, Josefa Macuada, Daniel Lagos, Duxan Arancibia, María E Andrés, Patrick Yu-Wai-Man, György Hajnóczky, Verónica Eisner.

Autosomal Dominant Optic Atrophy (ADOA), a disease that causes blindness and other neurological disorders, is linked to OPA1 mutations. OPA1, dependent on its GTPase and GED domains, governs inner mitochondrial membrane (IMM) fusion and cristae organization, which are central to oxidative metabolism. Mitochondrial dynamics and IMM organization have also been implicated in Ca2+ homeostasis and signaling but the specific involvements of OPA1 in Ca2+ dynamics remain to be established. Here we studied the possible outcomes of OPA1 and its ADOA-linked mutations in Ca2+ homeostasis using rescue and overexpression strategies in Opa1-deficient and wild-type murine embryonic fibroblasts (MEFs), respectively and in human ADOA-derived fibroblasts. MEFs lacking Opa1 required less Ca2+ mobilization from the endoplasmic reticulum (ER) to induce a mitochondrial matrix [Ca2+] rise ([Ca2+]mito). This was associated with closer ER-mitochondria contacts and no significant changes in the mitochondrial calcium uniporter complex. Patient cells carrying OPA1 GTPase or GED domain mutations also exhibited altered Ca2+ homeostasis, and the mutations associated with lower OPA1 levels displayed closer ER-mitochondria gaps. Furthermore, in Opa1 -/- MEF background, we found that acute expression of OPA1 GTPase mutants but no GED mutants, partially restored cytosolic [Ca2+] ([Ca2+]cyto) needed for a prompt [Ca2+]mito rise. Finally, OPA1 mutants' overexpression in WT MEFs disrupted Ca2+ homeostasis, partially recapitulating the observations in ADOA patient cells. Thus, OPA1 modulates functional ER-mitochondria coupling likely through the OPA1 GED domain in Opa1 -/- MEFs. However, the co-existence of WT and mutant forms of OPA1 in patients promotes an imbalance of Ca2+ homeostasis without a domain-specific effect, likely contributing to the overall ADOA progress.

Keywords: ADOA; OPA1; calcium; endoplasmic reticulum; mitochondria

DOI: https://doi.org/10.3389/fcell.2021.774108

STAR Protoc. 2022 Mar 18. 3(1): 101028

Microfluidic separation of axonal and somal compartments of neural progenitor cells differentiated in a 3D matrix.

Madhura S Lotlikar, Marina B Tarantino, Mehdi Jorfi, Dora M Kovacs, Rudolph E Tanzi, Raja Bhattacharyya.

This protocol describes the differentiation of human neural progenitor cells (hNPCs) in a microfluidic device containing a thin 3D matrix with two separate chambers, enabling a cleaner separation between axons and soma/bulk neurons. We have used this technique to study how mitochondria-associated ER membranes (MAMs) regulate the generation of somal and axonal amyloid β (Aβ) in FAD hNPCs, a cellular model of Alzheimer's disease. This protocol also details the quantification of Aβ molecules and isolation of pure axons via axotomy. For complete details on the use and execution of this profile, please refer to Bhattacharyya et al. (2021).

Keywords: Biotechnology and bioengineering; Cell Biology; Cell culture; Cell-based Assays; Neuroscience; Stem Cells

DOI: https://doi.org/10.1016/j.xpro.2021.101028