Biology subjects

Nandurkar, H.

Publications and source records attributed to Nandurkar, H..

3 recordsLinked to original sources

bioRxiv2023

Dysregulated expression of Hoxa1 isoforms in hematopoietic stem and progenitor cells causes myelodysplastic syndromes.

The homeobox gene, Hoxa1, has two different isoforms generated by alternative splicing: a full-length homeodomain-containing Hoxa1 (Hoxa1-FL), and a truncated Hoxa1 (Hoxa1-T), that lacks the homeodomain. The effects of the distinct Hoxa1 isoforms in hematopoiesis have not been investigated. Oncoretroviral studies revealed that Hoxa1-T acts in a dominant negative manner, regulating transcriptionally active Hoxa1. Oncoretroviral overexpression of wildtype Hoxa1 (WT-Hoxa1), which generates both Hoxa1 isoforms, in murine hematopoietic stem and progenitor cells (HSPCs) perturbed hematopoiesis, resulting in transplantable myelodysplastic syndromes (MDS) in mice. Overexpression of a mutated Hoxa1 cDNA (MUT-Hoxa1) that generates Hoxa1-FL, but not Hoxa1-T, led to a more severe MDS that transformed to secondary acute myeloid leukemia (sAML). DNA damage repair pathways were downregulated in Hoxa1-overexpressing hematopoietic progenitor cells, accompanied by increased {gamma}H2AX foci. In silico analyses revealed that CD34+ cells from approximately 50% of patients with MDS had elevated HOXA1-FL expression. Conditional knock-in WT-Hoxa1 and MUT-Hoxa1 mice were generated and had features of pre-MDS, developing altered hematopoiesis within 4 months of Hoxa1 isoform overexpression in HSPCs. HSPCs were significantly reduced in all knock-in mice, accompanied by significantly increased apoptosis in WT-Hoxa1 HSPCs. Healthy wildtype recipients transplanted with bone marrow cells from Hoxa1 knock-in mice developed trilineage MDS, with Hoxa1 isoform and gene dosage dependent phenotypes. Collectively our data identify a role for HOXA1 in the pathogenesis of MDS. Our Hoxa1 mouse models capture different stages of progression of disease from pre-MDS to MDS to sAML and provide novel, clinically relevant tools to study MDS. Key pointsHOXA1 is upregulated in approximately 50% of MDS patient CD34+ BM cells, highlighting a potential role for HOXA1 in the pathogenesis of MDS. Dysregulated expression of Hoxa1 isoforms in murine hematopoietic stem and progenitor cells predisposes mice to pre-MDS and MDS.

cancer biology↗

bioRxiv2022

N-Terminomic Changes of Neurons During Excitotoxicity Reveals Proteolytic Events Associated with Synaptic Dysfunctions and Potential Targets for Neuroprotection

Excitotoxicity is a neuronal death process initiated by over-stimulation of ionotropic glutamate receptors. Although dysregulation of proteolytic signaling networks is critical for excitotoxicity, the identity of affected proteins and mechanisms by which they induce neuronal cell death remain unclear. To address this, we used quantitative N-terminomics to identify proteins modified by proteolysis in neurons undergoing excitotoxic cell death. We found that most proteolytically processed proteins in excitotoxic neurons are likely substrates of calpains, including key synaptic regulatory proteins such as CRMP2, doublecortin-like kinase I, Src tyrosine kinase and calmodulin-dependent protein kinase II{beta} (CaMKII{beta}). Critically, calpain-catalyzed proteolytic processing of these proteins generates stable truncated fragments with altered activities that potentially contribute to neuronal death by perturbation of synaptic organization and function. Blocking calpain-mediated proteolysis of one of these proteins, Src protected against neuronal loss in a rat model of neurotoxicity. Extrapolation of our N-terminomic results led to the discovery that CaMKII, an isoform of CaMKII{beta} undergoes differential processing in mouse brains under physiological conditions and during ischemic stroke. In summary, our findings inform excitotoxic neuronal death mechanism and suggest potential therapeutic strategies for neuroprotection. In BriefAmeen, et al. used a proteomic method called N-terminomics to identify proteolytic events occurring in neurons during excitotoxicity. They found that most proteolytic processing is mediated by calpains, resulting in the generation of stable truncated fragments with the potential to induce synaptic dysfunction and loss, eventually leading to neuronal death. They further showed that some of these proteolytic processed proteins, such as the protein kinases Src and CaMKII, are potential targets for neuroprotection. HighlightsO_LIIdentification of over 300 neuronal proteins cleaved by calpains to form stable truncated fragments during excitotoxicity. C_LIO_LIThe calpain cleavage sites of these proteins unveil for the first time the preferred cleavage sequences of calpains in neurons. C_LIO_LIThese pathological proteolytic events potentially induce synaptic dysfunction and loss, which likely contribute to excitotoxic neuronal death. C_LIO_LISome of the neuronal proteins proteolyzed by calpains are potential targets of neuroprotection. C_LI Graphical abstract: Pathological proteolytic events in neurons during excitotoxicity unveiled by N-terminomic analyses(A) N-terminomic and global proteomic analyses identified neo-N-terminal sites and neuronal proteins undergoing significant abundance changes during excitotoxicity. (B) Informatic analysis of the proteomic results predicted (i) the preferred sequences of proteolytic processing of neuronal proteins catalyzed by calpains during excitotoxicity and (ii) perturbation of synaptic organization and functions as the major consequence of calpain-mediated proteolytic events. (C) Validation of these predictions and further experimentations unveiled: (i) calpain-mediated cleavage of proteins associated with synaptic damage in excitotoxic neurons, (ii) a new mechanism of dysregulation of CaMKII and CaMKII{beta}, which are key protein kinases governing synaptic dysfunctions and excitotoxic neuronal death and (iii) potential therapeutic targets such as the protein kinases Src and CaMKII for neuroprotection O_FIG O_LINKSMALLFIG WIDTH=194 HEIGHT=200 SRC="FIGDIR/small/484119v2_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@1c69873org.highwire.dtl.DTLVardef@142db3forg.highwire.dtl.DTLVardef@481521org.highwire.dtl.DTLVardef@6359e2_HPS_FORMAT_FIGEXP M_FIG C_FIG One Sentence SummaryProteolytic events in neurons during excitotoxicity inform neuronal death mechanism and potential therapeutic strategies for neuroprotection.

neuroscience↗

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↗