bims-mecosi 2026-09-13 papers

Issue of 2026–09–13
three papers selected by
Verena Kohler, Umeå University

Ageing Res Rev. 2026 Sep 06. pii: S1568-1637(26)00344-2. [Epub ahead of print]122 103352

Mitochondria-endoplasmic reticulum contact sites (MERCS/MAM): Multi-layered upstream regulators of microglial senescence in Alzheimer's disease.

Annan Liu, Liping Xing, Jianhui Li, Wei Gao, Mingyuan Yao, Jing Song, Honglin Li.

BACKGROUND: Alzheimer's disease (AD) is an age-dependent neurodegenerative syndrome in which microglial senescence bridges biological ageing and Aβ-tau pathology. Senescent microglia undergo permanent cell-cycle arrest, upregulate p16INK4a and SA-β-gal, and secrete a pro-inflammatory senescence-associated secretory phenotype (SASP) that sustains chronic neuroinflammation. Mitochondria-endoplasmic reticulum contact sites (MERCS) are dynamic physical junctions between the endoplasmic reticulum (ER) and mitochondria, whereas mitochondria-associated membranes (MAM) are biochemically enriched ER subdomains located at MERCS. MERCS coordinate calcium shuttling, mitochondrial dynamics, lipid trafficking and the unfolded protein response (UPR); however, whether their dysfunction drives microglial senescence in vivo remains largely untested.
MAIN TEXT: This review critically integrates five MERCS-linked signalling axes that are hypothesised to drive microglial senescence, namely calcium overload, mitochondrial fission-fusion imbalance, inflammatory amplification, lipid dysregulation and unresolved ER stress. We apply a standardized four-tier evidence-grading framework to stratify causal evidence, systematically distinguish dystrophic, disease-associated (DAM) and bona-fide senescent microglia on the basis of transcriptomic and proteomic data from AD models and human tissues, and address underexplored dimensions including APOE/TREM2 crosstalk, mitophagy, epigenetic regulation, peripheral inflammation and senolytic combinations. We stress that inflammatory activation, oxidative stress and mitochondrial dysfunction represent common cellular stress responses that cannot independently define bona-fide microglial senescence. Because more than 90% of current mechanistic evidence is derived from non-microglial models, MERCS dysfunction in microglia remains a compelling hypothesis that requires rigorous in-vivo validation. Notably, MERCS dysfunction and AD-relevant APOE/TREM2 signalling engage in mutually modulatory crosstalk rather than a simple linear upstream-downstream hierarchy.
CONCLUSION: Translational development faces several barriers, including poor blood-brain barrier (BBB) penetration, off-target neurotoxicity, uncharacterised long-term safety and limited generalisability from APP/PS1 models lacking tauopathy. All MERCS-targeted and senolytic combinatorial strategies discussed herein represent prospective pre-clinical research directions rather than mature clinical therapeutic approaches. We propose an experimental roadmap based on conditional knockouts, intravital imaging and bidirectional interventions. Overall, MERCS dysfunction is proposed as a candidate multimodal upstream hub for calcium, mitochondrial, inflammatory, lipid and ER-stress signalling, and rigorous in-vivo validation together with microglia-selective delivery platforms is essential for therapeutic translation.

Keywords: Alzheimer's disease; Lipid metabolism; Microglial senescence; Mitochondria–endoplasmic reticulum contact sites; Neuroinflammation; Senolytics

DOI: https://doi.org/10.1016/j.arr.2026.103352

J Ginseng Res. 2026 Sep;50(5): 101069

Direct targeting of ORAI1 by ginsenoside Rg3 modulates calcium signaling and senescence-associated AMPK-NRF2 activation.

Sooyeon Lee, Minjeong Ko, Ho Jeong Kwon.

Background: 20(S)-ginsenoside Rg3 (Rg3(S)), a major saponin derived from red ginseng, exhibits diverse biological activities, including antioxidant and anti-senescence effects. However, the direct molecular targets through which Rg3(S) regulates calcium signaling and its role at membrane contact sites during cellular senescence remain largely unknown.
Methods: Plasma membrane (PM)-endoplasmic reticulum (ER) contacts and related protein interactions were analyzed using proximity ligation assays and co-immunoprecipitation. Direct binding of Rg3(S) to ORAI1 was validated using cellular thermal shift assays and microscale thermophoresis. Molecular docking simulations followed by site-directed mutagenesis were used to define critical binding residues. Cytosolic calcium levels and cellular senescence were assessed using calcium imaging and senescence-associated β-galactosidase staining.
Results: Rg3(S) increased cytosolic calcium levels independently of ER calcium depletion and was accompanied by a reduction in PM-ER contacts. Rg3(S) directly bound to ORAI1 in a dose-dependent manner, identifying ORAI1 as a previously unrecognized molecular target of ginsenoside Rg3. Molecular docking revealed LYS204 and ILE229 within the extracellular loop of ORAI1 as key residues maintaining this interaction. Mutation of these residues abolished Rg3(S)-induced calcium influx, leading to impaired activation of the AMPK-NRF2 pathway and attenuation of the anti-senescence effect of Rg3(S).
Conclusion: These findings identify ORAI1 as a key molecular mediator of ginsenoside Rg3(S)-induced calcium signaling linked to cellular senescence. By modulating PM-ER contact sites and cytosolic calcium dynamics, Rg3(S) attenuates senescence, providing new mechanistic insight into the anti-aging potential of ginseng-derived compounds beyond autophagy-centered pathways.

Keywords: Calcium signaling; Cellular senescence; Ginsenoside-Rg3; ORAI1; Plasma membrane-endoplasmic reticulum contacts

DOI: https://doi.org/10.1016/j.jgr.2026.101069

Front Aging Neurosci. 2026 ;18 1884207

Striatal small RNA remodeling in MPTP-induced Parkinson's disease highlights coordinated downregulation of mitochondrial tsRNAs.

Mingyu Mao, Yan Wang, Qing Deng, Jun Xiang, Wentao Li.

Parkinson's disease (PD) is characterized by progressive nigrostriatal degeneration, yet the contribution of modification-rich small RNAs to PD pathology remains unclear. Here, we used PANDORA-seq to profile the striatal small RNA landscape in a subacute MPTP-induced mouse model of PD. MPTP-treated mice exhibited significant motor deficits together with reduced striatal tyrosine hydroxylase and dopamine transporter expression, confirming successful model establishment. Small RNA profiling revealed that transfer RNA-derived small RNAs and ribosomal RNA-derived small RNAs, rather than microRNAs, dominated the striatal small RNA transcriptome. Among the dysregulated small RNA classes, mitochondrial tsRNAs showed the most prominent and coordinated downregulation. Bioinformatic analysis suggested that predicted targets of differentially expressed mt-tsRNAs were enriched in synaptic organization, presynaptic function, membrane contact sites, and lipid-related pathways. In SH-SY5Y cells, transfection of an mt-tsRNA mimic partially reversed MPP+ induced increases in reactive oxygen species and restored mitochondrial membrane potential. These findings provide a modification-aware small RNA landscape of the PD striatum and identify mt-tsRNA downregulation as a notable feature of MPTP-induced parkinsonism.

Keywords: MPTP; Parkinson’s disease; mitochondrial dysfunction; mitochondrial tsRNAs; pANDORA-seq; striatum

DOI: https://doi.org/10.3389/fnagi.2026.1884207