Biology subjects

Eisert, R. J.

Publications and source records attributed to Eisert, R. J..

5 recordsLinked to original sources

bioRxiv2025

A conserved mechanism for the retrieval of polyubiquitinated proteins from cilia

The temporospatial distribution of proteins within cilia is regulated by intraflagellar transport (IFT), wherein molecular trains shuttle between the cell body and cilium. Defects in this process impair various signal-transduction pathways and cause ciliopathies. Although K63-linked ubiquitination appears to trigger protein export from cilia, the mechanisms coupling polyubiquitinated proteins to IFT remain unclear. Using a multidisciplinary approach, we demonstrate that a complex of CFAP36, a conserved ciliary protein of previously unknown function, and ARL3, a GTPase involved in ciliary import, binds polyubiquitinated proteins and links them to retrograde IFT trains. CFAP36 uses a coincidence detection mechanism to simultaneously bind two IFT subunits accessible only in retrograde trains. Depleting CFAP36 accumulates K63-linked ubiquitin in cilia and disrupts Hedgehog signaling, a pathway reliant on the retrieval of ubiquitinated receptors. These findings advance our understanding of ubiquitin-mediated protein transport and ciliary homeostasis, and demonstrate how structural changes in IFT trains achieve cargo selectivity.

molecular biology↗

bioRxiv2025

Gut Microbiome-Produced Bile Acid Metabolite Lengthens Circadian Period in Host Intestinal Cells

Host circadian signaling, feeding, and the gut microbiome are tightly interconnected. Changes in the gut microbial community can affect the expression of core clock genes, but the specific metabolites and molecular mechanisms that mediate this relationship remain largely unknown. Here, we sought to identify gut microbial metabolites that impact circadian signaling. Through a phenotypic screen of a focused library of gut microbial metabolites, we identified a bile acid metabolite, lithocholic acid (LCA), as a circadian modulator. LCA lengthened the circadian period of core clock gene hPer2 transcription in a dose-responsive manner in human colonic cells. We found evidence that LCA modulates the casein kinase 1 {delta}/{varepsilon} (CK1{delta}/{varepsilon})-protein phosphatase 1 (PP1) feedback loop and stabilizes core clock protein cryptochrome 2 (CRY2). Furthermore, we showed that LCA feeding alters circadian transcription in mouse distal ileum and colon. Taken together, our work identifies LCA as a molecular link between host circadian biology and the microbiome. Because bile acids are secreted in response to feeding, our work provides potential mechanistic insight into the molecular nature of the food-entrainable oscillator by which peripheral clocks adapt to the timing of food intake. Given the association between circadian rhythm, feeding, and metabolic disease, our insights may offer a new avenue for modulating host health.

cell biology↗

bioRxiv2023

A Spatiotemporal Map of Co-Receptor Signaling Networks Underlying B Cell Activation

The B cell receptor (BCR) signals together with a multi-component co-receptor complex to initiate B cell activation in response to antigen binding. This process underlies nearly every aspect of proper B cell function. Here, we take advantage of peroxidase-catalyzed proximity labeling combined with quantitative mass spectrometry to track B cell co-receptor signaling dynamics from 10 seconds to 2 hours after BCR stimulation. This approach enables tracking of 2,814 proximity-labeled proteins and 1,394 quantified phosphosites and provides an unbiased and quantitative molecular map of proteins recruited to the vicinity of CD19, the key signaling subunit of the co-receptor complex. We detail the recruitment kinetics of essential signaling effectors to CD19 following activation, and then identify new mediators of B cell activation. In particular, we show that the glutamate transporter SLC1A1 is responsible for mediating rapid metabolic reprogramming immediately downstream of BCR stimulation and for maintaining redox homeostasis during B cell activation. This study provides a comprehensive map of the BCR signaling pathway and a rich resource for uncovering the complex signaling networks that regulate B cell activation.

immunology↗

bioRxiv2022

A Spatiotemporal Notch Interaction Map from Membrane to Nucleus

Notch signaling relies on ligand-induced proteolysis to liberate a nuclear effector that drives cell fate decisions. The location and timing of individual steps required for proteolysis and movement of Notch from membrane to nucleus, however, remain unclear. Here, we use proximity labeling with quantitative multiplexed mass spectrometry to monitor the microenvironment of endogenous Notch2 after ligand stimulation in the presence of a gamma secretase inhibitor and then as a function of time after inhibitor removal. Our studies show that gamma secretase cleavage of Notch2 occurs in an intracellular compartment and that formation of nuclear complexes and recruitment of chromatin-modifying enzymes occurs within 45 minutes of inhibitor washout. This work provides a spatiotemporal map of unprecedented detail tracking the itinerary of Notch from membrane to nucleus after activation and identifies molecular events in signal transmission that are potential targets for modulating Notch signaling activity.

molecular biology↗

bioRxiv2020

Multiplexed proteomics and imaging of resolving and lethal SARS-CoV-2 infection in the lung

Normal tissue physiology and repair depends on communication with the immune system. Understanding this communication at the molecular level in intact tissue requires new methods. The consequences of SARS-CoV-2 infection, which can result in acute respiratory distress, thrombosis and death, has been studied primarily in accessible liquid specimens such as blood, sputum and bronchoalveolar lavage, all of which are peripheral to the primary site of infection in the lung. Here, we describe the combined use of multiplexed deep proteomics with multiplexed imaging to profile infection and its sequelae directly in fixed lung tissue specimens obtained from necropsy of infected animals and autopsy of human decedents. We characterize multiple steps in disease response from cytokine accumulation and protein phosphorylation to activation of receptors, changes in signaling pathways, and crosslinking of fibrin to form clots. Our data reveal significant differences between naturally resolving SARS-CoV-2 infection in rhesus macaques and lethal COVID-19 in humans. The approach we describe is broadly applicable to other tissues and diseases. SummaryProteomics of infected tissue reveals differences in inflammatory and thrombotic responses between resolving and lethal COVID-19.

pathology↗