Biology subjects

Chaurasiya, S.

Publications and source records attributed to Chaurasiya, S..

3 recordsLinked to original sources

bioRxiv2023

Intricate mechanism (s) of substrate specificity and loss of function on disease mutation (K211N) of Parkin

PINK1 and Parkin mutations lead to the early onset of Parkinsons disease. PINK1-mediated phosphorylation of its substrates such as ubiquitin (Ub), ubiquitin-like protein (NEDD8), and ubiquitin-like (Ubl) domain of Parkin activate autoinhibited Parkin E3 ligase. The mechanism of various phospho-Ubls binding on Parkin and conformational changes leading to Parkin activation remain elusive. Herein, we determine the first crystal structure of human Parkin E3 ligase bound with phospho (p)-NEDD8, which shows that NEDD8 has evolved over Ub to bind and activate Parkin more robustly. X-ray crystal structures and supporting biophysical/biochemical data reveal specific recognition and underlying mechanisms of pUb/pNEDD8 and pUbl domain binding to the RING1 and RING0 domains, respectively. This new data also shows that pUb/pNEDD8 binding in the RING1 pocket causes allosteric conformational changes in Parkins catalytic domain (RING2), leading to Parkin activation. Furthermore, Parkinsons disease mutation K211N in the RING0 domain of Parkin was believed to lose its activation due to loss of interaction with pUb. However, our data reveal allosteric conformational changes due to N211 that lock RING2 with RING0 to inhibit Parkin K211N activity without disrupting pNEDD8/pUb binding. This study would aid the design of small-molecule Parkin activators for the treatment of Parkinsons disease.

biochemistry↗

bioRxiv2023

Anaplerotic nutrient stress drives synergy of angiogenesis inhibitors with therapeutics targeting tumor metabolism

Tumor angiogenesis is a cancer hallmark, and its therapeutic inhibition has provided meaningful, albeit limited, clinical benefit. While anti-angiogenesis inhibitors deprive the tumor of oxygen and essential nutrients, cancer cells activate metabolic adaptations to diminish therapeutic response. Despite these adaptations, angiogenesis inhibition incurs extensive metabolic stress, prompting us to consider such metabolic stress as an induced vulnerability to therapies targeting cancer metabolism. Metabolomic profiling of angiogenesis-inhibited intracranial xenografts showed universal decrease in tricarboxylic acid cycle intermediates, corroborating a state of anaplerotic nutrient deficit or stress. Accordingly, we show strong synergy between angiogenesis inhibitors (Avastin, Tivozanib) and inhibitors of glycolysis or oxidative phosphorylation through exacerbation of anaplerotic nutrient stress in intracranial orthotopic xenografted gliomas. Our findings were recapitulated in GBM xenografts that do not have genetically predisposed metabolic vulnerabilities at baseline. Thus, our findings cement the central importance of the tricarboxylic acid cycle as the nexus of metabolic vulnerabilities and suggest clinical path hypothesis combining angiogenesis inhibitors with pharmacological cancer interventions targeting tumor metabolism for GBM tumors.

cancer biology↗

bioRxiv2019

Estrogen receptor β exerts tumor suppressive effects in prostate cancer through repression of androgen receptor activity

Estrogen receptor {beta} (ER{beta}) was first identified in the rodent prostate and is abundantly expressed in human and rodent prostate epithelium, stroma, immune cells and endothelium of the blood vessels. In the prostates of mice with inactivated ER{beta}, mutant phenotypes include epithelial hyperplasia and increased expression of androgen receptor (AR)-regulated genes, most of which are also upregulated in prostate cancer (PCa). ER{beta} is expressed in both basal and luminal cells in the prostate while AR is expressed in luminal but not in the basal cell layer which harbors the prostate stem cells. To investigate the mechanisms of action of ER{beta} and its potential cross-talk with AR, we used RNA-seq to study the effects of estradiol or the synthetic ligand, LY3201, in AR-positive LNCaP PCa cells which had been engineered to express ER{beta}. Transcriptomic analysis indicated relatively few changes in gene expression with ER{beta} overexpression, but robust responses following ligand treatments. There is significant overlap of responsive genes between the two ligands, as well as ligand-specific alterations. Gene set analysis of down-regulated genes identified an enrichment of androgen-responsive genes, such as FKBP5, CAMKK2, and TBC1D4. Consistently, AR transcript, protein levels, and transcriptional activity were down-regulated following ER{beta} activation. In agreement with this, we find that the phosphorylation of the CAMKK2 target, AMPK, was repressed by ligand-activated ER{beta}. Down-regulation of TBC1D4, a major regulator of glucose uptake in prostate, indicates that ER{beta} is changing glucose metabolism in the prostate. These findings suggest that ER{beta}-mediated signaling pathways are involved in the negative regulation of AR expression and activity, thus supporting a tumor suppressive role for ER{beta} in PCa.

cancer biology↗