Torres, E. R. | bioRxiv Science

bioRxiv2023

Sex Chromosomes and Gonads Shape the Sex-Biased Transcriptomic Landscape in Tlr7-Mediated Demyelination During Aging

Demyelination occurs in aging and associated diseases, including Alzheimers disease. Several of these diseases exhibit sex differences in prevalence and severity. Biological sex primarily stems from sex chromosomes and gonads releasing sex hormones. To dissect mechanisms underlying sex differences in demyelination of aging brains, we constructed a transcriptomic atlas of cell type-specific responses to illustrate how sex chromosomes, gonads, and their interaction shape responses to demyelination. We found that sex-biased oligodendrocyte and microglial responses are driven by interaction of sex chromosomes and gonads prior to myelin loss. Post demyelination, sex chromosomes mainly guide microglial responses, while gonadal composition influences oligodendrocyte signaling. Significantly, ablation of the X-linked gene Toll-like receptor 7 (Tlr7), which exhibited sex-biased expression during demyelination, abolished the sex-biased responses and protected against demyelination. One-sentence summaryCell type-specific processes underlying aged demyelination are sex-biased and mediated by Tlr7.

neuroscience↗

bioRxiv2022

A small molecule probe elucidates the role of mitochondrial translocase TIMM44 in PINK1/Parkin regulated mitophagy

Neurodegenerative diseases have been linked to a dysfunctional mitochondrial quality control system that is partially maintained by proteins PINK1 and Parkin. Whereas mitophagy pathways are becoming well-characterized, less is known about the molecular mechanisms of PINK1 trafficking in mitochondria. Accordingly, we have used a small molecule probe (MitoBloCK-10/MB-10) that modulates the activity of TIMM44, an essential component of the protein associated motor (PAM) complex for the mitochondrial inner membrane (TIM23) translocase, to characterize PINK1 import. MB-10 did not inhibit the import or degradation of PINK1 in energized mitochondria. However, when mitophagy was induced by the addition of an uncoupler or respiratory inhibitor, MB-10 treatment altered PINK1 trafficking by inhibiting association with the TOM complex and impairing Parkin recruitment and subsequent mitophagy. MB-10 analogs that did not inhibit TIMM44 activity failed to impair mitophagy, thereby assigning specificity to MB-10. Because PINK1 undergoes lateral release from the TIM23 translocon to interact with inner membrane (IM) modulators, our studies support that TIMM44 may be a key regulator and that the PAM complex has a central role in regulating PINK1-dependent mitophagy. Our studies also provide a probe for dissecting PINK1/Parkin events for mitochondria as well as studying PINK1-dependent mitophagy in cell and animal models.

biochemistry↗