bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/687533

Peroxisome turnover and diurnal modulation of antioxidant activity in retinal pigment epithelia utilizes microtubule-associated protein 1 light chain 3B

Daniele, L. L.·Caughey, J.·Volland, S.·Sharp, R. C.·Dhingra, A.·Williams, D. S.·Philp, N. J.·Boesze-Battaglia, K.
View original source ↗Export metadata ↓

Abstract

The retinal pigment epithelium (RPE) supports the outer retina through essential roles in the retinoid the visual cycle, nutrient supply, ion exchange and waste removal. Each day the RPE removes the oldest [~]10% of photoreceptor outer segments through phagocytic uptake, which peaks in a synchronous burst following light onset. Impaired degradation of phagocytosed OS material by the RPE can lead to toxic accumulation of lipids, oxidative tissue damage, inflammation and cell death. OSs are rich in very long chain fatty acids which are preferentially catabolized in peroxisomes. Despite the importance of lipid degradation in RPE function, the regulation of peroxisome number and activity relative to diurnal OS ingestion is relatively unexplored. Using immunohistochemistry, immunoblotting and catalase activity assays, we investigated peroxisome abundance and activity at 6 am, 7 am (at lights on), 8 am, and 3 pm, in WT mice and mice lacking microtubule-associated protein 1 light chain 3B (LC3B), that have impaired degradation of phagosomes. We found that catalase activity, but not protein expression, is 50% higher in the morning compared with 3 pm, in RPE of WT but not LC3B-/- mice. Surprisingly, we found that peroxisome abundance was stable during the day, however numbers are elevated overall in LC3B-/- mice, implicating LC3B in autophagic organelle turnover in RPE. Our data suggest that RPE peroxisome function is regulated in coordination with phagocytosis, possibly through direct enzyme regulation, and may serve to prepare RPE peroxisomes for daily surges in ingested lipid-rich OS.

Source connections

Explore related subjects

biochemistryPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Daniele, L. L., Caughey, J., Volland, S., Sharp, R. C., Dhingra, A., Williams, D. S., Philp, N. J., Boesze-Battaglia, K.. 2019-07-01. Peroxisome turnover and diurnal modulation of antioxidant activity in retinal pigment epithelia utilizes microtubule-associated protein 1 light chain 3B. https://doi.org/10.1101/687533

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Structural basis for inefficient G protein coupling by Frizzled receptors

Frizzleds (FZDs) are class F G protein-coupled receptors (GPCRs) that primarily signal through Dishevelled (DVL) to initiate Wnt signalling, with evidence for context-specific coupling to heterotrimeric G proteins. Every FZD-G protein structure to date has been determined without an agonist, implying that agonist binding is not required for stable complex formation in vitro and directly contradicting the difficulty of demonstrating G protein coupling in cells. All these structures contain unassigned density between the receptor and the heterotrimeric G protein. From structures generated by single-particle cryo-electron microscopy (cryo-EM) of FZD7-Gs and FZD5-Gq, we identify this density as the detergent lauryl maltose neopentyl glycol (LMNG), which bridges the receptor and G protein to stabilise a weak, shallow interface. Absence of LMNG - in biochemical preparations and molecular dynamics simulations - destabilises the complex, showing that constitutive FZD-G protein engagement is intrinsically weak. The weak G protein coupling is governed by a conserved intracellular interface that when mutated differentially influences DVL and G protein signalling. Our findings show that LMNG has masked the instability of purified FZD-G protein complexes and provide the structural basis of FZDs as inherently weak G protein activators that are predisposed to DVL signalling.

biochemistry↗
bioRxiv2026

A Binuclear Cluster Supports Functional Asymmetry in Dark-Operative Protochlorophyllide Reductase

Many photosynthetic bacteria rely on the nitrogenase-like dark-operative protochlorophyllide oxidoreductase (DPOR) to sustain (bacterio)chlorophyll synthesis in the dark. DPOR couples ATP hydrolysis to electron transfer from a reducing component (L-protein) to a catalytic component (NB-protein) that reduces protochlorophyllide. NB-protein is an 2{beta}2 heterotetramer, and each heterodimeric half contains an active site and a [Fe4S4] cluster. Although the two halves are identical, they react sequentially rather than in parallel. How the two halves communicate has remained unknown. Here we show, using Cu K-edge x-ray absorption spectroscopy and cryo-EM, that the NB-protein tetramer interface holds a binuclear, sulfur-bridged [Cu2S2] cluster. Each Cu is reduced and three-coordinate, with short Cu-S and Cu-Cu distances (2.26 and 2.62 &Aring). Mutagenesis excludes the nearest cysteine as the bridging ligand, supporting inorganic sulfide as the most likely sulfur donor. To our knowledge, this is the first sulfide-bridged dicopper cluster identified in a protein. The cluster is conserved in three purple non-sulfur bacteria and connects the BchB C-terminal helices that contact opposing active sites. Loss of Cu abolishes DPOR activity and asymmetric L-protein binding without disturbing overall fold. We propose that the cluster relays substrate-binding information between active sites, suggesting a metal-mediated mechanism for cooperativity in nitrogenase-like enzymes.

biochemistry↗
bioRxiv2026

Jade1S SUMOylates tau and targets oligomers for degradation

The accumulation of insoluble tau aggregates is a pathological hallmark of tauopathies, including Alzheimer's disease. While molecular chaperones and clearance pathways regulate tau homeostasis, the mechanisms governing tau oligomerization and degradation remain incompletely defined. Recent genome-wide association studies (GWAS) have linked the JADE1 locus to tauopathy, and the PHD zinc finger protein Jade1S has been identified in complexes with tau in post-mortem brain tissue, prompting investigation into their biochemical relationship. Here, we characterize the reciprocal interactions between Jade1S and 0N4R tau stability and turnover. Covalent labeling mass spectrometry and co-immunoprecipitation mappings reveal that Jade1S binds wild-type 0N4R tau through redundant sites within its N-terminal and plant homeodomain (PHD) zinc finger domains. In vitro assays demonstrate that Jade1S functions as a SUMO E3 ligase, utilizing its PHD domains to mediate tau SUMOylation. Cell-based cycloheximide chase assays reveal a reciprocal stabilization dynamic: tau co-expression extends the overall physiological half-life of Jade1S from less than an hour to ~17 hours, arresting its turnover specifically within sarkosyl-insoluble fractions. Conversely, Jade1S selectively accelerates the degradation of sarkosyl-insoluble tau without altering the turnover of the soluble monomeric pool over chased time. Mechanistically, Jade1S redirects the clearance of SUMO2/3-modified tau oligomers away from basal autophagic-lysosomal pathways and toward proteasome-dependent degradation. Furthermore, Jade1S exhibits intrinsic molecular chaperone activity, inhibiting arachidonic acid-induced tau oligomerization in vitro. Together, these data characterize Jade1S as a dual-function SUMO ligase and chaperone that regulates tau stability, prevents oligomer assembly, and promotes the targeted proteasomal clearance of aggregated tau.

biochemistry↗