Biology subjects

Pagan, J.

Publications and source records attributed to Pagan, J..

4 recordsLinked to original sources

bioRxiv2026

Germline mitophagy selectively eliminates deleterious mitochondrial DNA across generations

Faithful transmission of genetic information through the immortal germline is essential for organismal health and species survival, yet how mutant mitochondrial genomes (mtDNAs) are selectively eliminated across generations remains unclear. Here, we show that germline mitophagy functions as a mutation-responsive surveillance system that selectively eliminates mutant mtDNAs and shapes inheritance across generations. In C. elegans, mitochondria enriched for mutant mtDNAs are selectively removed in the maternal germline prior to oocyte fertilization via PINK1/Parkin-dependent and BNIP3-mediated mitophagy pathways activated by mtDNA defects. Germline mitophagy declines with age, resulting in offspring that inherit increased burdens of mutant mtDNAs. Conversely, enhancing mitophagy within germ cells restricts the transmission of deleterious genomes in a compounding manner, ultimately driving their complete elimination from the matrilineal lineage. Together, our findings demonstrate that germline mitophagy is a critical determinant of intergenerational mitochondrial genome inheritance, establishing its role in restricting the transmission of defective genetic information.

Cell Biology↗

bioRxiv2023

Pptc7 maintains mitochondrial protein content by suppressing receptor-mediated mitophagy

Pptc7 is a resident mitochondrial phosphatase essential for maintaining proper mitochondrial content and function. Newborn mice lacking Pptc7 exhibit aberrant mitochondrial protein phosphorylation, suffer from a range of metabolic defects, and fail to survive beyond one day after birth. Using an inducible knockout model, we reveal that loss of Pptc7 in adult mice causes marked reduction in mitochondrial mass concomitant with elevation of the mitophagy receptors Bnip3 and Nix. Consistently, Pptc7-/- mouse embryonic fibroblasts (MEFs) exhibit a major increase in mitophagy that is reversed upon deletion of these receptors. Our phosphoproteomics analyses reveal a common set of elevated phosphosites between perinatal tissues, adult liver, and MEFs-- including multiple sites on Bnip3 and Nix. These data suggest that Pptc7 deletion causes mitochondrial dysfunction via dysregulation of several metabolic pathways and that Pptc7 may directly regulate mitophagy receptor function or stability. Overall, our work reveals a significant role for Pptc7 in the mitophagic response and furthers the growing notion that management of mitochondrial protein phosphorylation is essential for ensuring proper organelle content and function.

biochemistry↗

bioRxiv2022

FBXL4 suppresses mitophagy by restricting the accumulation of NIX and BNIP3 mitophagy receptors

Cells selectively remove damaged or excessive mitochondria through mitophagy, a specialized form of autophagy, to maintain mitochondrial quality and quantity. Mitophagy is induced in response to diverse conditions, including hypoxia, cellular differentiation, and mitochondrial damage. However, the mechanisms by which cells remove specific dysfunctional mitochondria under steady-state conditions to fine-tune mitochondrial content are not well understood. Here, we report that SCFFBXL4, an SKP1/CUL1/F-box protein ubiquitin ligase complex, localizes to the mitochondrial outer membrane in unstressed cells and mediates the constitutive ubiquitylation and degradation of the mitophagy receptors NIX and BNIP3 to suppress basal levels of mitophagy. We demonstrate that, unlike wild-type FBXL4, pathogenic variants of FBXL4 that cause encephalopathic mtDNA depletion syndrome (MTDPS13), do not efficiently interact with the core SCF ubiquitin ligase machinery or mediate the degradation of NIX and BNIP3. Thus, we reveal a molecular mechanism that actively suppresses mitophagy via preventing NIX and BNIP3 accumulation and propose that excessive basal mitophagy in the FBXL4-associated mtDNA depletion syndrome is caused by dysregulation of NIX and BNIP3 turnover. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=195 SRC="FIGDIR/small/511867v1_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@19c97f6org.highwire.dtl.DTLVardef@1bca5a3org.highwire.dtl.DTLVardef@1e9419org.highwire.dtl.DTLVardef@18d28a9_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2020

Functional modulation of T follicular cells in vivo enhances antigen-specific humoral immunity

Generation of high-affinity IgG is essential for defense against infections and cancer, is the intended consequence of many vaccines, but can cause autoimmune and inflammatory diseases when inappropriately directed against self (Wang et al., 2018, Ludwig et al., 2017, Chinen et al., 2010). The interplay and balance of T follicular helper cells (TFH) and T follicular regulatory cells (TFR) is critical for production of high-affinity IgG (Wing et al., 2018). Here, we empowered TFH cells and improve antigen-specific IgG responses with two interventions intended to transiently diminish TFR influence. First, adult mice were administered an antibiotic cocktail (ABX) for an extended period to deplete the immunoregulatory intestinal microbiota (Belkaid and Harrison, 2017, Thaiss et al., 2016, Rooks and Garrett, 2016, Honda and Littman, 2016, Perruzza et al., 2017, Teng et al., 2016, Block et al., 2016, Proietti et al., 2014, Slack et al., 2014). This treatment skewed T follicular cell ratios, with increased TFH and reduced TFR numbers. TNP-KLH immunization resulted in higher affinity TNP-specific IgG in ABX mice compared to controls. In a model of IgG-driven inflammatory nephritis, ABX mice had significantly worse nephritis accompanied by higher affinity antigen-specific IgG, and enriched TFH cells compared to controls. Second, we sought to functionally manipulate TFH and TFH cells, which both express the checkpoint inhibitory molecule, PD-1 (Sage et al., 2013), by administration of -PD-1 during immunization. This intervention enhanced the affinity of antigen-specific IgG and increased in TFH following TNP-KLH immunization and nephritis induction. These results suggest that altering TFH and TFR ratio during immunization is an appealing strategy to qualitatively improve IgG responses.

immunology↗