Biology subjects

Dhillon, A.

Publications and source records attributed to Dhillon, A..

3 recordsLinked to original sources

bioRxiv2021

Dual MAPK and HDAC inhibition rewires the apoptotic rheostat to trigger colorectal cancer cell death

The EGFR/RAS/MEK/ERK signalling pathway (ERK/MAPK) is hyper-activated in most colorectal cancers (CRCs). A current limitation of inhibitors of this pathway is that they primarily induce cytostatic effects in CRC cells. Nevertheless, these drugs do induce expression of pro-apoptotic factors, suggesting they may prime CRC cells to undergo apoptosis. As histone deacetylase inhibitors (HDACi) induce expression of multiple pro-apoptotic proteins, we examined whether they could synergize with ERK/MAPK inhibitors to trigger CRC cell apoptosis. Combined MEK/ERK and HDAC inhibition synergistically induced apoptosis in CRC cell lines and patient-derived tumour organoids in vitro, and attenuated Apc-initiated adenoma formation in vivo. Mechanistically this effect was mediated through induction of the BH3-only pro-apoptotic proteins BIM and BMF. Importantly, we demonstrate that this treatment paradigm can be tailored to specific MAPK genotypes in CRCs, by combining HDACi with EGFR, KRASG12C or BRAFV600 inhibitors in KRAS/BRAFWT; KRASG12C, BRAFV600E CRC cell lines respectively. These findings identify a novel ERK/MAPK genotype-targeted treatment paradigm for colorectal cancer.

cancer biology↗

bioRxiv2020

Molecular basis for B. pertussis interference with complement, coagulation, fibrinolytic and contact activation systems: The cryo-EM structure of the Vag8-C1 inhibitor complex

Complement, contact activation, coagulation, and fibrinolysis are serum protein cascades that need strict regulation to maintain human health. Serum glycoprotein, C1-inhibitor (C1-INH) is a key regulator (inhibitor) of serine proteases of all the above-mentioned pathways. Recently, an autotransporter protein, Virulence Associated Gene 8 (Vag8) produced by the whopping cough causing pathogen, Bordetella pertussis has been shown to bind and interfere with C1-INH function. Here we present the structure of Vag8: C1-INH complex determined using cryo-electron microscopy at 3.6 [A] resolution. The structure shows a unique mechanism of C1-INH inhibition not employed by other pathogens where Vag8 sequesters the Reactive Centre Loop of the C1-INH preventing its interaction with the target proteases. ImportanceThe structure 105 kDa protein complex is one of the smallest to be determined using cryo-electron microscopy at high resolution. The mechanism of disrupting C1-INH revealed by the structure is crucial to understand how pathogens by producing a single virulence factor can disturb several homeostasis pathways. Virulence mechanisms such as the one described here assume more importance given the emerging evidence about dysregulation of contact activation, coagulation and fibrinolysis leading to COVID-19 pneumonia.

microbiology↗

bioRxiv2020

An Atlas of Phosphorylation and Proteolytic Processing Events During Excitotoxic Neuronal Death Reveals New Therapeutic Opportunities

Excitotoxicity, a neuronal death process in neurological disorders, is initiated by over-stimulation of neuronal ionotropic glutamate receptors. The over-stimulated receptors dysregulate proteases, protein kinases and phosphatases, which in turn modify target neuronal proteins to induce cell death. To decipher this cell death mechanism, we used quantitative proteomics, phosphoproteomics and N-terminomics to identify modified proteins in excitotoxic neurons. Data, available in ProteomeXchange (identifiers: PXD019527 and PXD019211), enabled us to identify over one thousand such proteins with calpains, cathepsins and over twenty protein kinases as their major modifiers. These protein modification events can potentially perturb signalling pathways governing cell survival, synaptogenesis, axonal guidance and mRNA processing. Importantly, blocking the modification of Src protein kinase, a signalling hub in excitotoxic neurons, protected against neuronal loss in vivo in a rat model of neurotoxicity. Besides offering new insights into excitotoxic neuronal death mechanism, our findings suggest potential neuroprotective therapeutic targets for treating neurological disorders. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=162 SRC="FIGDIR/small/151456v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@1f0191forg.highwire.dtl.DTLVardef@17ba2org.highwire.dtl.DTLVardef@15c0848org.highwire.dtl.DTLVardef@123d28b_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIMulti-dimensional proteomic analysis identified proteins modified by proteolysis and altered phosphorylation in neurons undergoing excitotoxic cell death. C_LIO_LICalpains, cathepsins and over twenty protein kinases are major modifiers of these proteins. C_LIO_LIThese protein modification events are predicted to impact cell survival, axonal guidance, synaptogenesis and mRNA processing. C_LIO_LIBlocking modification of an identified protein Src, which acts as a major signalling hub in neurons, was protective against excitotoxic injury in vivo. C_LI In BriefUsing multidimensional proteomic approaches, Ameen, et al. mapped the changes of proteome, phosphoproteome and N-terminome of cultured primary neurons during excitotoxicity, a crucial neuronal death process in neurological disorders. These proteomic changes document new excitotoxicity-associated molecular events, and offer insights into how these events are organized to induce neuronal death. Potential therapeutic relevance of these molecular events is illustrated by the demonstration that in vivo blockade of one of these events could protect against excitotoxic neuronal loss.

biochemistry↗