Biology subjects

Chang, R. B.

Publications and source records attributed to Chang, R. B..

3 recordsLinked to original sources

bioRxiv2024

A widespread family of viral sponge proteins reveals specific inhibition of nucleotide signals in anti-phage defense

Cyclic oligonucleotide-based antiviral signaling systems (CBASS) are bacterial anti-phage defense operons that use nucleotide signals to control immune activation. Here we biochemically screen 57 diverse E. coli and Bacillus phages for the ability to disrupt CBASS immunity and discover anti-CBASS 4 (Acb4) from the Bacillus phage SPO1 as the founding member of a large family of >1,300 immune evasion proteins. A 2.1 [A] crystal structure of Acb4 in complex with 3'3'-cGAMP reveals a tetrameric assembly that functions as a sponge to sequester CBASS signals and inhibit immune activation. We demonstrate Acb4 alone is sufficient to disrupt CBASS activation in vitro and enable immune evasion in vivo. Analyzing phages that infect diverse bacteria, we explain how Acb4 selectively targets nucleotide signals in host defense and avoids disruption of cellular homeostasis. Together, our results reveal principles of immune evasion protein evolution and explain a major mechanism phages use to inhibit host immunity.

microbiology↗

bioRxiv2023

Differential developmental blueprints of organ-intrinsic nervous systems

The organ-intrinsic nervous system is a major interface between visceral organs and the brain, mediating important sensory and regulatory functions in the body-brain axis and serving as critical local processors for organ homeostasis. Molecularly, anatomically, and functionally, organ-intrinsic neurons are highly specialized for their host organs. However, the underlying mechanism that drives this specialization is largely unknown. Here, we describe the differential strategies utilized to achieve organ-specific organization between the enteric nervous system (ENS)1 and the intrinsic cardiac nervous system (ICNS)2, a neuronal network essential for heart performance but poorly characterized. Integrating high-resolution whole-embryo imaging, single-cell genomics, spatial transcriptomics, proteomics, and bioinformatics, we uncover that unlike the ENS which is highly mobile and colonizes the entire gastrointestinal (GI) tract, the ICNS uses a rich set of extracellular matrix (ECM) genes that match with surrounding heart cells and an intermediate dedicated neuronal progenitor state to stabilize itself for a beads-on-the-necklace organization on heart atria. While ICNS- and ENS-precursors are genetically similar, their differentiation paths are influenced by their host-organs, leading to distinct mature neuron types. Co-culturing ENS-precursors with heart cells shifts their identity towards the ICNS and induces the expression of heart-matching ECM genes. Our cross-organ study thus reveals fundamental principles for the maturation and specialization of organ-intrinsic neurons.

neuroscience↗

bioRxiv2023

GDF15 is a Critical Renostat in the Defense Against Hypoglycemia

Episodic hypoglycemia is one of the best honed, evolutionary conserved phenomena in biology, because of the constant feast-fast cycles that have characterized most of history. The counterregulatory response to hypoglycemia, mobilizing substrate stores to produce glucose, is the primary adaptive mechanism to enable survival. Catecholamines and glucagon have long been considered the key hypoglycemia counterregulatory hormones, but here we identify a new hypoglycemia counterregulatory factor. We employed the insulin tolerance test (ITT) and hyperinsulinemic-hypoglycemic clamp to mimic the two common settings in which hypoglycemia can occur in patients: postprandial insulin overdose and elevated basal insulin administration, respectively. We found that Growth Differentiation Factor 15 (GDF15) production is induced in the S3 segment of the renal proximal tubules and its release increases hepatic gluconeogenesis by increasing intrahepatic lipolysis in a beta-adrenergic receptor-2 (Adrb2)-dependent manner. In addition, mice exposed to recurrent hypoglycemia and patients with T1D exhibit impaired GDF15 production in the setting of hypoglycemia. These data demonstrate that GDF15 acts acutely as a gluco-counterregulatory hormone and identify a critical role for kidney-derived GDF15 in glucose homeostasis under physiological and pathophysiological conditions.

physiology↗