Biology subjects

Sole-Domenech, S.

Publications and source records attributed to Sole-Domenech, S..

3 recordsLinked to original sources

bioRxiv2026

Intravital pH Imaging using the sensor ApHID Reveals Incomplete Lysosomal Acidification in Resident Meningeal Phagocytes.

Tracking lysosomes and quantifying their pH in the living, intact brain has been challenging owing to the lack of suitable in vivo tools. Here we report the use of dextran polymers labeled with the pH sensor ApHID to visualize and quantify lysosomal pH in mouse brain resident phagocytes. ApHID-dextrans delivered systemically are rapidly endocytosed by phagocytes in the meninges -mainly dural and subdural macrophages- and accumulate in lysosomal compartments. Intravital pH imaging revealed a striking heterogeneity in lysosomal acidification, with only ~5% of meningeal phagocytes reaching pH values below 5.0, in marked contrast with measurements in macrophage cell cultures. Photothrombotic ischemic lesions induced progressive lysosomal acidification in local phagocytes, while acute chloroquine treatment led to rapid alkalinization. Our methodology enables direct, quantitative pH measurements without genetic manipulations, and unveils a previously unappreciated heterogeneity in lysosomal acidification among brain-resident myeloid cells.

neuroscience↗

bioRxiv2026

Impaired lipoprotein secretion by APOE4 leads to lysosomal and mitochondrial dysfunction in human microglia

While Apolipoprotein E4 (APOE4) is the greatest known genetic risk factor for late-onset Alzheimers disease, its mechanistic role in the brain-resident macrophage, microglia, remains elusive. Microglia are important in the clearance of pathology in disease, heavily relying on lysosome functionality; therefore, we sought to understand the impact of APOE4 on microglial function. APOE44 microglia have been shown to have lipid accumulation, yet the mechanisms leading to this accumulation are unknown. Using induced pluripotent stem cell-derived microglia, we found that the APOE4 haplotype resulted in transcriptional state shifts in microglia, suppressing activated-response microglia (ARMs) and promoting a G2 senescent-like state. We found that APOE44 microglia accumulate cholesterol esters and provide less lipid support to fibroblast-induced neurons, decreasing their synaptic connections. APOE44 microglia secrete significantly less lipoproteins, leading to the accumulation of lipoproteins within the cells including the lysosomes. APOE44 microglia exhibit impaired lysosomal acidification and degradation capacity. Further, our results elucidated that APOE44 microglia are proinflammatory and shift away from fatty acid oxidation towards glycolysis, due to dysfunctional mitochondria. Taken together, our findings indicate that a loss-of-function in lipoprotein secretion drives intracellular lipid accumulation, including within lysosomes, ultimately disrupting the lysosome-endoplasmic reticulum-mitochondrial axis. This drives a proinflammatory and metabolically compromised microglial phenotype with impaired neuro-supportive functions. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=138 SRC="FIGDIR/small/724612v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@18d6a2org.highwire.dtl.DTLVardef@b3644dorg.highwire.dtl.DTLVardef@17e3716org.highwire.dtl.DTLVardef@1529caf_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2024

Ratiometric pH Imaging of Macrophage Lysosomes Using the Novel pH-sensitive Dye ApHID.

Lysosomes actively regulate their lumenal pH, which is necessary for optimal enzymatic activity. Endocytic processes are involved in many diseases, including Alzheimers disease, in which sub-optimal lysosomal function has been reported. To measure acidification, pH-sensitive probes can be delivered to endosomes and lysosomes using labeled dextran polymers or proteins. However, many commercially available probes have limited sensitivity in the acidic range of lysosomes, and their fluorescence is subject to enzymatic degradation and photobleaching. Herein, we describe the preparation, characterization, and use of a novel pH-sensitive probe, ApHID, a green-emitting fluorescent dye with optimal dynamic range within the acidity of endosomes and lysosomes. ApHID has a pKa near 5, increasing brightness with acidity, and it is robustly resistant to oxidation and photobleaching. We used ApHID ratiometric imaging to measure lysosomal pH in macrophages, yielding virtually identical results when compared with fluorescein and Oregon Green. Overall, ApHID circumvents limitations presented by most commercially available pH-sensitive probes and can be useful in demanding imaging applications such as intravital imaging of tissues.

biochemistry↗