Biology subjects

Laughlin, T. G.

Publications and source records attributed to Laughlin, T. G..

8 recordsLinked to original sources

bioRxiv2026

Peroxisome quality control is gated by a dynamic ATF6α-ABCD3 tether

The endoplasmic reticulum (ER) coordinates protein folding and lipid biosynthesis, while peroxisomes govern fatty-acid catabolism and redox balance. However, little is known about the mechanisms by which these organelles communicate. Here we show that activating transcription factor 6 (ATF6), a cytoprotective ER-resident sensor of the unfolded protein response (UPR), forms a molecular tether that zippers the ER and peroxisomes together at a 23-nm intermembrane distance. ATF6 achieves this by inserting a short segment of its unstructured N-terminal cytosolic tail into the solvated transmembrane cavity of the peroxisomal ABC-type lipid transporter ABCD3, trapping it in an off-state. This interaction is reinforced by Ceapin, a previously identified small molecule molecular-glue ligand, which promotes ER-peroxisome contact formation. The junctions serve as a scaffold that can initiate peroxisome turnover by p62-triggered autophagy (pexophagy), as enhanced lipid processing resulting from organelle zippering leads to peroxisome damage due to excessive reactive oxygen species (ROS) accumulation. These findings define ATF6 as a non-transcriptional regulator of organelle quality control and provide a template for engineering Ceapin analogues against ATF6/ABCD3-dependent colorectal and hepatocellular cancers and related diseases.

cell biology↗

bioRxiv2026

Stereoselective methyl-swapping demonstrates target specificity of cognitive enhancer

The Integrated Stress Response (ISR) couples cellular stress sensing to translational control, playing a critical role in the homeostatic regulation of cell health. However, prolonged and unmitigated ISR activation becomes maladaptive and drives the progression of a wide range of pathologies, including cognitive decline. Pharmacological inhibition of the ISR with the small, drug-like molecule ISRIB has proven remarkably effective in reversing cognitive deficits and pathology in animal models, highlighting its potential for therapeutic intervention in humans. We engineered an allele-specific ISRIB analog (mISRIB) that selectively targets a mutant form of eIF2B, the molecular target of ISRIB, without affecting wild-type eIF2B. Notably, mISRIB treatment in mice homozygous for the eIF2B mutant allele enhances synaptic plasticity and long-term memory, confirming the on-target mechanism underlying ISRIBs cognitive benefits. Our results provide a framework for dissecting the ISRs contributions within complex cellular networks, such as those governing brain function, with precise temporal and spatial resolution.

biochemistry↗

bioRxiv2023

A mobile intron facilitates interference competition between co-infecting viruses

Mobile introns containing homing endonucleases are widespread in nature and have long been assumed to be selfish elements that provide no benefit to the host organism. These genetic elements are common in viruses, but whether they confer a selective advantage is unclear. Here we studied a mobile intron in bacteriophage {Phi}PA3 and found its homing endonuclease gp210 contributes to viral competition by interfering with the virogenesis of co-infecting phage {Phi}KZ. We show that gp210 targets a specific sequence in its competitor {Phi}KZ, preventing the assembly of progeny viruses. This work reports the first demonstration of how a mobile intron can be deployed to engage in interference competition and provide a reproductive advantage. Given the ubiquity of introns, this selective advantage likely has widespread evolutionary implications in nature.

microbiology↗

bioRxiv2023

Identifying the core genome of the nucleus-forming bacteriophage family and characterization of Erwinia phage RAY

We recently discovered that some bacteriophages establish a nucleus-like replication compartment (phage nucleus), but the core genes that define nucleus-based phage replication and their phylogenetic distribution were unknown. By studying phages that encode the major phage nucleus protein chimallin, including previously sequenced yet uncharacterized phages, we discovered that chimallin-encoding phages share a set of 72 highly conserved genes encoded within seven distinct gene blocks. Of these, 21 core genes are unique to this group, and all but one of these unique genes encode proteins of unknown function. We propose that phages with this core genome comprise a novel viral family we term Chimalliviridae. Fluorescence microscopy and cryo-electron tomography studies of Erwinia phage vB_EamM_RAY confirm that many of the key steps of nucleus-based replication encoded in the core genome are conserved among diverse chimalliviruses, and reveal that non-core components can confer intriguing variations on this replication mechanism. For instance, unlike previously studied nucleus-forming phages, RAY doesnt degrade the host genome, and its PhuZ homolog appears to form a five-stranded filament with a lumen. This work expands our understanding of phage nucleus and PhuZ spindle diversity and function, providing a roadmap for identifying key mechanisms underlying nucleus-based phage replication.

microbiology↗

bioRxiv2022

Architecture and self-assembly of the jumbo bacteriophage nuclear shell

Bacteria encode myriad defenses that target the genomes of infecting bacteriophage, including restriction-modification and CRISPR/Cas systems. In response, one family of large bacteriophage employs a nucleus-like compartment to protect their replicating genomes by excluding host defense factors. However, the principle composition and structure of this compartment remain unknown. Here, we find that the bacteriophage nuclear shell assembles primarily from one protein, termed chimallin. Combining cryo-electron tomography of nuclear shells in bacteriophage-infected cells and cryo-electron microscopy of a minimal chimallin compartment in vitro, we show that chimallin cooperatively self-assembles as a flexible sheet into closed micron-scale compartments. The architecture and assembly dynamics of the chimallin shell suggest mechanisms for its nucleation and growth, and its role as a scaffold for phage-encoded factors mediating macromolecular transport, cytoskeletal interactions, and viral maturation.

biophysics↗

bioRxiv2021

Discovery of a carbonic anhydrase-Rubisco supercomplex within the alpha-carboxysome

Carboxysomes are proteinaceous organelles that encapsulate key enzymes of CO2 fixation - Rubisco and carbonic anhydrase - and are the centerpiece of the bacterial CO2 concentrating mechanism (CCM). In the CCM, actively accumulated cytosolic bicarbonate diffuses into the carboxysome and is converted to CO2 by carbonic anhydrase, producing a high CO2 concentration near Rubisco and ensuring efficient carboxylation. Self-assembly of the -carboxysome is orchestrated by the intrinsically disordered scaffolding protein, CsoS2, which interacts with both Rubisco and carboxysomal shell proteins, but it is unknown how the carbonic anhydrase, CsoSCA, is incorporated into the -carboxysome. Here, we present the structural basis of carbonic anhydrase encapsulation into -carboxysomes from Halothiobacillus neapolitanus. We find that CsoSCA interacts directly with Rubisco via an intrinsically disordered N-terminal domain. A 1.98 [A] single-particle cryo-electron microscopy structure of Rubisco in complex with this peptide reveals that CsoSCA binding is predominantly mediated by a network of hydrogen bonds. CsoSCAs binding site overlaps with that of CsoS2 but the two proteins utilize substantially different motifs and modes of binding, revealing a plasticity of the Rubisco binding site. Our results advance the understanding of carboxysome biogenesis and highlight the importance of Rubisco, not only as an enzyme, but also as a central hub for mediating assembly through protein interactions.

biochemistry↗

bioRxiv2021

A Cytoskeletal Vortex Drives Phage Nucleus Rotation During Jumbo Phage Replication inE. coli

Vortex-like arrays of cytoskeletal filaments that drive cytoplasmic streaming and nucleus rotation have been identified in eukaryotes, but similar structures have not been described in prokaryotes. The only known example of a rotating intracellular body in prokaryotic cells occurs when nucleus-forming jumbo phages infect Pseudomonas. During infection, a bipolar spindle of PhuZ filaments drives intracellular rotation of the phage nucleus, a key aspect of the replication cycle. Here we show the E. coli jumbo phage Goslar assembles a phage nucleus surrounded by an array of PhuZ filaments resembling a vortex instead of a bipolar spindle. Expression of mutant PhuZ strongly reduces Goslar phage nucleus rotation, demonstrating that the PhuZ cytoskeletal vortex is necessary for rotating the phage nucleus. While vortex-like cytoskeletal arrays are important in eukaryotes, this work identifies the first known example of a coherent assembly of filaments into a vortex-like structure driving intracellular rotation within the prokaryotic cytoplasm.

microbiology↗

bioRxiv2018

Genome-wide screening reveals a novel class of carbonic anhydrase-like inorganic carbon transporters in chemoautotrophic bacteria

Many bacterial autotrophs rely on CO2 concentrating mechanisms (CCMs) to assimilate carbon. Although many CCM proteins have been identified, including a 200+ MDa protein organelle called the carboxysome, a systematic screen of CCM components has not been carried out. Here, we performed a genome-wide barcoded transposon screen to identify essential and CCM-related genes in the {gamma}-proteobacterium H. neapolitanus. Our screen revealed an operon encoding a domain of unknown function (PFAM:PF10070) and putative cation transporter subunit (PFAM:PF00361) is critical for CCM function. These two proteins, which we name DabA and DabB for \"DABs accumulate bicarbonate,\" function as a heterodimeric, energy-coupled inorganic carbon pump in E. coli. Furthermore, DabA has distant homology to a {beta}-carbonic anhydrase and binds a zinc ion necessary for activity. Based on these results, we propose that DABs function as vectorial CAs coupled to cation gradients and serve as inorganic carbon pumps throughout prokaryotic phyla.

molecular biology↗