Biology subjects

Krantz, S.

Publications and source records attributed to Krantz, S..

3 recordsLinked to original sources

bioRxiv2022

Parallel Activation of Src and Hif1α Increases Localized Glycolytic ATP Generation for Re-assembly of Endothelial Adherens Junctions

Endothelial adherens junctions (AJs) are critical for the regulation of vascular barrier integrity and undergo dis-assembly during inflammatory injury, thus causing vascular leakiness. AJ re-assembly is thus necessary for restoration of the endothelial barrier following the initial injury. Here we examine the metabolic underpinnings that drive restoration of vascular integrity. In response to inflammatory stimuli, the glycolysis regulatory enzyme PFKFB3 is activated, resulting in a rapid and sustained increase of intracellular glycolytic ATP, especially in the proximity of AJs at the plasma membrane. We engineered a novel chemo-genetic construct (RapT) which allowed for precise temporal control of PFKFB3 recruitment to the plasma membrane. Activation of RapT by rapamycin during the barrier restoration phase increased regional ATP and accelerated AJ re-assembly. Mechanistically, we observed that PFKFB3 is activated through two modes. Src-mediated post-translational phosphorylation rapidly increases PFKFB3 activity. Using another chemo-genetic approach to temporally control Src activity, we found that Src activates PFKFB3 by binding to and phosphorylating it at residues Y175, Y334, and Y363. Tyrosine-phospho-deficient mutants of PFKFB3 at these residues block the glycolytic activation upon inflammatory stimuli. In parallel, elevated reactive oxygen species generated during inflammatory stimulation create pockets of regional hypoxia and allow for increased Hif1-mediated transcription of PFKFB3, leading to sustained glycolytic activation. Moreover, inhibition of PFKFB3 delays AJ reassembly and restoration of vascular integrity both in vitro and in vivo. In conclusion, we show that while inflammatory activation acutely compromises the endothelial barrier, inflammatory signaling also concomitantly generates a metabolic milieu in anticipation of the subsequent re-assembly of AJs and restoration of the vascular barrier.

cell biology↗

bioRxiv2022

Pink1-mediated mitophagy in the endothelium releases proteins encoded by mitochondrial DNA and activates neutrophil responses

Given their ancient evolutionary origins, eukaryotic mitochondria possess multiple vestiges of their prokaryotic ancestors. One such factor is the N-terminal formylation of proteins encoded by mitochondrial DNA. N-formylated proteins are also released by bacteria and trigger activation of immune cells such as neutrophils. Growing evidence indicate that circulating levels of mitochondrial formyl proteins are elevated in the serum of patients with excessive inflammatory responses and trigger neutrophil activation like their bacterial counterparts. However, the cellular source of these proteins, and the mechanism by which they are released into the circulation is not known. In this study, we have identified vascular endothelial cells as a source of mitophagy induced release of formyl proteins in response to inflammatory mediators in vitro. Mechanistically, endothelial mitophagy required activation of the Pink1 pathway. Using liposomal delivery of sgRNA targeting Pink1 in mice expressing endothelial-specific Cas9, we developed a mouse model in which Pink1 is specifically depleted in the endothelium. Deletion of endothelial Pink1 was remarkably protective in endotoxin-induced lung inflammation, resulting in reduced neutrophil infiltration and significantly reduced death in mice. We thus propose that endothelial cells upregulate pro-inflammatory mitophagy in response to inflammation, leading to release of mitochondrial formyl peptides and detrimental neutrophil recruitment into the lung.

cell biology↗

bioRxiv2021

Mathematical Analysis and Topology of SARS-CoV-2, Bonding with Cells and Unbonding

AO_SCPLOWBSTRACTC_SCPLOWWe consider the structure of the novel coronavirus (SARS-Cov-2) in terms of the number of spikes that are critical in bonding with the cells in the host. Bonding formation is considered for selection criteria with and without any treatments. Functional mappings from the discrete space of spikes and cells and their analysis are performed. We found that careful mathematical constructions help in understanding the treatment impacts, and the role of vaccines within a host. Smales famous 2-D horseshoe examples inspired us to create 3-D visualizations and understand the topological diffusion of spikes from one human organ to another organ. The pharma industry will benefit from such an analysis for designing efficient treatment and vaccine strategies.

pharmacology and toxicology↗