Biology subjects

Rathore, R.

Publications and source records attributed to Rathore, R..

6 recordsLinked to original sources

bioRxiv2024

p53 isoforms have a high aggregation propensity, interact with chaperones and lack binding to p53 interaction partners

The p53 transcription factor family consists of the three members p53, p63 and p73. Both p63 and p73 exist in different isoforms that are well characterized. Isoforms have also been identified for p53 and it has been proposed that they are responsible for increased cancer metastasis. In contrast to the p63 and p73 isoforms, which do not contain truncations in folded domains, most of the p53 isoforms contain only parts of either the DNA binding domain or the oligomerization domain. To better understand the effect of p53 isoforms in cancer we provide here a comprehensive biochemical characterization. With the exception of the {Delta}40p53 isoform none of the other variants can bind to DNA with high affinity and none can upregulate transcription. Probing with antibodies, DARPins and other interaction partners confirmed that isoforms harboring deletions in the DNA binding domain cannot interact specifically with them, but instead are bound to chaperones and other factors known to interact with misfolded proteins. Expression of isoforms with deletions in the DNA binding domain results in upregulation of cellular chaperones. If the expression level surpasses a threshold, the chaperone system can no longer keep these isoforms soluble resulting in aggregation and co-aggregation with other factors.

biophysics↗

bioRxiv2024

BRAT1 - a new therapeutic target for glioblastoma

Glioblastoma (GBM), the most malignant primary brain tumor in adults, has poor prognosis irrespective of therapeutic advances due to its radio-resistance and infiltrative growth into brain tissue. The present study assessed functions and putative druggability of protein breast cancer type 1 susceptibility protein (BRCA1)-associated Ataxia telangiectasia mutated (ATM)-activator 1 (BRAT1) as a crucial factor driving key aspects of GBM, including enhanced DNA damage response and tumor migration. By a stable depletion of BRAT1 in GBM and glioma stem-like (GSC) cell lines, we observed a delay in DNA double-strand break repair and increased sensitivity to radiation treatment, corroborated by in vitro and in vivo studies demonstrating impaired tumor growth and invasion. Proteomic analyses further emphasize the role of BRAT1s cell migration and invasion capacity, with a notable proportion of downregulated proteins associated with these processes. In line with the genetic manipulation, we found that treatment with the BRAT1 inhibitor Curcusone D (CurD) significantly reduced GSC migration and invasion in an ex vivo slice culture model, particularly when combined with irradiation, resulting a synergistic inhibition of tumor growth and infiltration. Our results reveal that BRAT1 contributes to GBM growth and invasion and suggest that therapeutic inhibition of BRAT1 with CurD or similar compounds might constitute a novel approach for anti-GBM directed treatments.

cancer biology↗

bioRxiv2023

Serine ubiquitination of p62 regulates Nrf2 dependent redox homeostasis

The KEAP1-Nrf2 axis is essential for the cellular response against metabolic and oxidative stress. KEAP1 is an adaptor protein of Cullin-3 ubiquitin ligase that controls the cellular levels of Nrf2, a critical transcription factor of several cytoprotective genes. Oxidative stress, defective autophagy and pathogenic infections activate Nrf2 signaling through phosphorylation of the adaptor protein p62, which competes with Nrf2 for binding to KEAP1. Here we show that phosphoribosyl-linked serine ubiquitination of p62 catalyzed by SidE effectors of Legionella pneumophila controls Nrf2 signaling and cell metabolism upon Legionella infection. Serine ubiquitination of p62 sterically blocks its binding to KEAP1, resulting in Nrf2 ubiquitination and degradation. This reduces Nrf2-dependent antioxidant synthesis in the early phase of infection. Levels of serine ubiquitinated p62 diminish in the later stage of infection allowing the expression of Nrf2-target genes; resulting in a differential regulation of the host metabolome and proteome in a Nrf2 dependent manner.

cell biology↗

bioRxiv2022

TBC1D15 potentiates lysosomal regeneration from damaged membranes

Acute lysosomal membrane damage reduces the cellular population of functional lysosomes. However, these damaged lysosomes have a remarkable recovery potential independent of lysosomal biogenesis and remain unaffected in TFEB/TFE3-depleted cells. We combined proximity labelling based proteomics, biochemistry and high-resolution microscopy to unravel a new lysosomal membrane regeneration pathway which is dependent on ATG8, lysosomal membrane protein LIMP2, the Rab7 GAP TBC1D15, and proteins required for autophagic lysosomal reformation (ALR) including Dynamin2, Kinesin5B and Clathrin. Upon lysosomal damage, LIMP2 act as a lysophagy receptor to bind ATG8, which in turn recruits TBC1D15 to damaged membranes. TBC1D15 hydrolyses Rab7-GTP to segregate the damaged lysosomal mass and provides a scaffold to assemble and stabilize the ALR machinery, potentiating the formation of lysosomal tubules and subsequent Dynamin2-dependent scission. TBC1D15-mediated lysosome regeneration was also observed in a cell culture model of oxalate nephropathy.

cell biology↗

bioRxiv2020

Systems level profiling of arginine starvation reveals MYC and ERK adaptive metabolic reprogramming

Arginine auxotrophy due to the silencing of argininosuccinate synthetase 1 (ASS1) occurs in many cancers, especially sarcomas. Arginine deiminase (ADI-PEG20) therapy exploits this metabolic vulnerability by depleting extracellular arginine, causing arginine starvation. ASS1-negative cells develop resistance to ADI-PEG20 through a metabolic adaptation that includes re-expressing ASS1. As arginine-based multiagent therapies are being developed, further characterization of the changes induced by arginine starvation is needed. In order to develop a systems-level understanding of these changes, activity-based proteomic profiling (ABPP) and phosphoproteomic profiling were performed before and after ADI-PEG20 treatment in ADI-PEG20-sensitive and resistant sarcoma cells. When integrated with previous metabolomic profiling (Kremer et al, 2017a), this multi-omic analysis reveals that cellular response to arginine starvation is mediated by adaptive ERK signaling, driving a Myc-Max transcriptional network. Concomitantly, these data elucidate proteomic changes that facilitate oxaloacetate production by enhancing glutamine and pyruvate anaplerosis, and altering lipid metabolism to recycle citrate for oxidative glutaminolysis. Based on the complexity of metabolic and cellular signaling interactions, these multi-omic approaches could provide valuable tools for evaluating response to metabolically targeted therapies.

cancer biology↗

bioRxiv2017

Partitioning of semisynthetic lipidated N-Ras in lipid raft nanodomains determined by FRET to lipid domain markers

Cellular membranes are heterogeneous planar lipid bilayers displaying lateral phase separation with the nanometer-scale liquid-ordered phase (aka \"lipid rafts\" or Lo) surrounded by the liquid-disordered phase (Ld). Many membrane-associated proteins were found to stably integrate in the rafts, which is critical for their biological function. Isoforms H and N of Ras GTPase possess a unique ability to switch their lipid domain preference depending on the type of bound guanine nucleotide (GDP or GTP). This behavior, however, has never been reproduced in vitro in model bilayers with recombinant proteins, and therefore has been attributed to action of other proteins binding Ras at the membrane surface. In this paper, we report the observation of the nucleotide-dependent switch of lipid domain preferences of the semisynthetic lipidated N-Ras in raft lipid vesicles in the absence of other proteins. To detect segregation of Ras molecules in raft and disordered lipid domains, we measured Forster Resonance Energy Transfer (FRET) between the donor fluorophore, mant, attached to the protein-bound guanine nucleotides, and the acceptor, rhodamine-conjugated lipid, localized to the liquid-disordered domains. We demonstrated that N-Ras preferentially populated raft domains when bound to mant-GDP, while losing preference for rafts when it was associated with a GTP mimic, mant-GppNHp. At the same time, the isolated lipidated C-terminal peptide of N-Ras was found localized outside of the liquid-ordered rafts, most likely--in the bulk disordered lipid.

biochemistry↗