Biology subjects

Chang, A. H.

Publications and source records attributed to Chang, A. H..

6 recordsLinked to original sources

bioRxiv2025

A microsporidial deubiquitinase blocks ubiquitin transfer from adenylated E1 to human UBE2K ubiquitin conjugating enzyme

Intracellular pathogens frequently subjugate the ubiquitin system to evade host immune defenses and establish intracellular replication niches. Microsporidia are obligate intracellular animal parasites that typically cause self-limiting infections in humans, but can sometimes cause fatal disseminated disease. At present, the ubiquitin system of microsporidia is virtually unexplored. Here, we discover a likely effector deubiquitinase (DUB) of the otubain subgroup from the human pathogenic microsporidian Encephalitozoon hellem, which we designate ehOTUB1. We find that ehOTUB1 selectively binds the human ubiquitin conjugating (E2) enzyme UBE2K and inhibits its ubiquitin conjugation activity independent of ehOTUB1 DUB activity. We show that ehOTUB1 obstructs docking of UBE2K onto ubiquitin E1 enzyme via steric conflict with ubiquitin in the E1 adenylation site to prevent ubiquitin transfer to UBE2K. This unconventional mechanism of E2 inhibition expands the known repertoire by which pathogens manipulate ubiquitin signaling, and suggests that direct inhibition of E2 enzymes may be a broader function of otubain subfamily DUBs than originally appreciated.

biochemistry↗

bioRxiv2025

Donor-Targeted Anti-HLA-A2 Antibody Shows Nanogram-Level Efficacy in a Novel GVHD Mouse Model

Acute graft-versus-host disease (GVHD) remains a life-threatening complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT), with limited treatment options for steroid-refractory cases. Current therapies broadly suppress immune responses, increasing infection risk and impairing graft function. We hypothesized that selective depletion of donor immune cells through HLA allele-specific targeting could offer a safer and more precise alternative. To test this, we developed a monoclonal antibody (AN7) against HLA-A2 by immunizing HLA-A24 transgenic mice with recombinant HLA-A2 tetramers, followed by hybridoma screening. AN7 specifically recognized HLA-A2 and HLA-A68, and was reformatted into murine IgG2a and human chimeric IgG1 recombinant antibodies. These retained binding specificity and mediated robust complement-dependent cytotoxicity (CDC), antibody-dependent cellular cytotoxicity (ADCC), and antibody-dependent cellular phagocytosis (ADCP) against HLA-A2+ target cells. To evaluate therapeutic potential, we established a fully MHC-mismatched allo-HSCT model using HLA-A2 transgenic donor bone marrow in lethally irradiated BALB/c recipients. A single ultra-low dose of AN7 (1-100 ng) administered post-transplant significantly improved survival and reduced GVHD while preserving donor hematopoiesis. These findings highlight the potential of allele-specific antibody-mediated clearance as a mechanistically distinct approach to donor immune modulation in GVHD.

immunology↗

bioRxiv2023

Chromosomal instability can favor macrophage-mediated immune response and induce a broad, vaccination-like anti-tumor IgG response

Chromosomal instability (CIN), a state in which cells undergo mitotic aberrations that generate chromosome copy number variations, generates aneuploidy and is thought to drive cancer evolution. Although associated with poor prognosis and reduced immune response, CIN generates aneuploidy-induced stresses that could be exploited for immunotherapies. In such contexts, macrophages and the CD47-SIRP checkpoint are understudied. Here, CIN is induced pharmacologically induced in poorly immunogenic B16F10 mouse melanoma cells, generating persistent micronuclei and diverse aneuploidy while skewing macrophages towards an anti-cancer M1-like phenotype, based on RNA-sequencing profiling, surface marker expression and short-term antitumor studies. These results further translate to in vivo efficacy: Mice bearing CIN-afflicted tumors with wild-type CD47 levels survive only slightly longer relative to chromosomally stable controls, but long-term survival is maximized when combining macrophage-stimulating anti-tumor IgG opsonization and some form of disruption of the CD47-SIRP checkpoint. Survivors make multi-epitope, de novo anti-cancer IgG that promote macrophage-mediated phagocytosis of CD47 knockout B16F10 cells and suppress tumoroids in vitro and growth of tumors in vivo. CIN does not greatly affect the level of the IgG response compared to previous studies but does significantly increase survival. These results highlight an unexpected therapeutic benefit from CIN when paired with maximal macrophage anti-cancer activity: an anti-cancer vaccination-like antibody response that can lead to more durable cures and further potentiate cell-mediated acquired immunity.

cancer biology↗

bioRxiv2020

Dach1 extends artery networks and protects against cardiac injury

Coronary artery disease (CAD) is the leading cause of death worldwide, but there are currently no available methods to stimulate growth or regeneration of artery networks in diseased hearts. Studying how arteries are built during embryonic development could illuminate strategies for re-building these vessels in the setting of ischemic heart disease. We previously found, using loss-of-function experiments, that the transcription factor Dach1 is required for coronary artery development in mouse embryos. Here, we report that Dach1 overexpression in endothelial cells (ECs) extended coronary arteries and improved survival and heart function in adult mice following myocardial infarction (MI). Dach1 overexpression increased the length and number of arterial end branches, in both heart and retinal vasculature, by causing additional capillary ECs to differentiate into arterial ECs and contribute to growing arteries. Single-cell RNA sequencing (scRNAseq) of ECs undergoing Dach1-induced arterial specification indicated that it potentiated normal artery differentiation, rather than functioning as a master regulator of artery cell fate. ScRNAseq also showed that normal arterial differentiation is accompanied by repression of lipid metabolism genes, which were also repressed by Dach1 prior to arterialization. Together, these results demonstrate that increasing the expression level of Dach1 is a novel pathway for driving specification of artery ECs and extending arterial vessels, which could be explored as a means of increasing artery coverage to mitigate the effects of CAD.

developmental biology↗

bioRxiv2020

Complement factor C1q mediates chronic neuron loss and inflammation post-brain injury

While traumatic brain injury (TBI) acutely disrupts the cortex, most TBI-related disabilities reflect secondary injuries that accrue over time. The thalamus is a likely site of secondary damage because of its reciprocal connections with the cortex. Using a mouse model of cortical injury that does not directly damage subcortical structures, we found a chronic increase in C1q expression specifically in the corticothalamic circuit. Increased C1q expression co-localized with neuron loss and chronic inflammation, and correlated with altered cortical rhythms. Blocking C1q counteracted most of these outcomes, suggesting that C1q is a disease modifier in TBI. Since the corticothalamic circuit is important for sensory processing, attention, cognition, and sleep, all of which can be impaired by TBI, this circuit could be a new target for treating TBI-related disabilities.

neuroscience↗

bioRxiv2020

Somatostatin-positive neurons in the reticular thalamus modulate gamma rhythms and visual information in mouse V1

Visual perception in natural environments depends on the ability to focus on salient stimuli while ignoring distractions. This kind of selective visual attention is associated with gamma activity in the visual cortex. While the nucleus reticularis thalami (nRT) has been implicated in selective attention, its role in modulating visual perception remains unknown. Here we show that somatostatin-(SOM) but not parvalbumin-expressing (PV) neurons in the nRT preferentially project to visual thalamic nuclei. In freely behaving mice, single-unit and field recordings reveal powerful modulation of both visual information transmission and gamma activity in primary visual cortex (V1), as well as in the dorsal lateral geniculate nucleus (dLGN). These findings pinpoint the SOM neurons in nRT as powerful modulators of the visual information encoding accuracy in V1, and represent a novel circuit through which the nRT can influence representation of visual information.

neuroscience↗