Biology subjects

Dror, S.

Publications and source records attributed to Dror, S..

6 recordsLinked to original sources

bioRxiv2026

HSPD1 promotes neuroblastoma by augmenting MYCN expression

MYCN amplification is associated with poor outcomes in neuroblastoma (NB). MYCN encodes a transcription factor that induces the expression of mitochondrial one-carbon enzymes and chaperones, promoting metabolic reprogramming and aggressiveness in NB tumor cells. While the contribution of MYCN to changes in the mitochondrial proteome is well established, how mitochondrial proteostasis contributes to MYCN activity remains poorly understood. Mitochondrial HSP60 (HSPD1) is a conserved mitochondrial chaperone promoting the mitochondrial one-carbon pathway and mitochondrial translation by folding the one-carbon enzyme MTHFD2 and preventing aggregation of mitochondrial ribosomal proteins. Here, we show that HSPD1 depletion in MYCN-amplified NB cells led to reduced mitochondrial translation, MYCN expression, and tumorigenesis in vitro and in vivo. In addition, HSPD1 mRNA and protein correlate with MYCN expression in NB tumors. These results establish HSPD1 as a promising target for the treatment of MYCN-amplified NB.

cancer biology↗

bioRxiv2026

The mitochondrial chaperone HSPD1 folds MTHFD2 independently of its co-chaperone HSPE1

Acquiring new cellular states entails metabolic reprogramming driven by changes in the expression of cytosolic and mitochondrial metabolic enzymes. Most mitochondrial proteins are synthesized in the cytosol and imported into the mitochondria in a linear form, after which they are folded by a network of mitochondrial chaperones and co-chaperones. Which mitochondrial protein is dependent upon which chaperone for its folding is largely unknown. HSPD1/HSPE1 (HSP60/HSP10) are evolutionarily conserved mammalian homologues of the bacterial proteins GroEL/GroES, forming a chamber-and-lid chaperonin to facilitate the folding of client proteins. We used gene knockdown and SILAC-based proteomics to identify HSPD1 client proteins. We found that HSPD1 supports the expression of Methylenetetrahydrofolate Dehydrogenase 2 (MTHFD2), a key essential protein in the mitochondrial one-carbon (1C) pathway, in cells and tumors, and directly folds MTHFD2, independently of its co-chaperone HSPE1. HSPD1 interacts with MTHFD2 in mitochondria, and MTHFD2 is degraded by LONP1 in HSPD1 knockdown cells. Consequently, we observed reduced nucleotide and S-adenosylmethionine (SAM) levels in HSPD1 knockdown and found minimal overlap in the transcriptional and metabolic cellular responses to HSPD1 vs. HSPE1 depletion. In C. elegans, knockout of HSP60 triggers the mitochondrial stress response in the gut, while HSP10 knockout triggers the mitochondrial stress response in muscle tissue. Our data support that HSPD1 is an MTHFD2 chaperone and that, in addition to working together, HSPD1 and HSPE1 have distinct biological functions.

cell biology↗

bioRxiv2025

Complementary cortical and thalamic contributions to cell-type-specific striatal activity dynamics during movement

Coordinated motor behavior emerges from information flow across brain regions. How long-range inputs drive cell-type-specific activity within motor circuits remains unclear. The dorsolateral striatum (DLS) contains direct- and indirect-pathway medium spiny neurons (dMSNs and iMSNs) with distinct roles in movement control. In mice performing skilled locomotion, we recorded from dMSNs, iMSNs, and their cortical and thalamic inputs identified by monosynaptic rabies tracing. An RNN classifier and clustering analysis revealed functionally heterogeneous subpopulations in each population, with dMSNs preferentially activated at movement onset and offset, and iMSNs during execution. Cortical and thalamic inputs were preferentially activated during onset/offset and execution, respectively, though dMSN- and iMSN-projecting neurons in each region showed similar patterns. Locomotion phase-specific rhythmic activity was found in a subset of thalamic dMSN-projecting neurons and dMSNs. Cortex or thalamus inactivation reduced MSN activity. These findings suggest that corticostriatal and thalamostriatal inputs convey complementary motor signals via shared and cell-type-specific pathways.

neuroscience↗

bioRxiv2025

Beyond translation initiation: dual regulatory interactions with phosphorylated and non-phosphorylated LeishIF4E1

Translation initiation in eukaryotes begins with the assembly of the cap-binding eIF4F complex at the 5 ends of mRNAs, through eIF4E. Among the six orthologs of eIF4E in Leishmania, LeishIF4E1 is intriguing, as it does not bind any Leishmania eIF4G. It is expressed in both life-forms, maintaining efficient cap-binding activity for translation initiation, unlike other LeishIF4Es. We identified two novel phosphorylation sites specifically S108, and S112, along with S203, which is conserved with the mammalian phosphorylation site. A non-phosphorylatable, tagged, mutant of LeishIF4E1 created by substituting the phosphorylated serine residues with alanine [S(108,112,203)A] was generated. The phosphorylation status did not affect the binding of LeishIF4E1 to translation initiation factors. However, the phosphorylated LeishIF4E1 interacted with proteins involved in DNA and chromatin structure, while non-phosphorylated LeishIF4E1 interacted with proteins that assist cells under stress and unfavorable conditions, particularly in gluconeogenesis. This suggests secondary regulatory roles for LeishIF4E1. RNA sequencing of the LeishIF4E1-associated transcripts revealed a tenfold reduction in transcripts binding to non-phosphorylated LeishIF4E1. GO enrichment analysis indicated distinct phosphorylation-dependent transcript specificities for each form. This study highlights the critical role of LeishIF4E1 phosphorylation in modulating the selectivity of protein interactome and transcript associations, extending the role of LeishIF4E1 beyond its well-established function in translation initiation. Author SummaryLeishmania are digenetic parasites that transition from sand fly vector to mammalian hosts, undergoing a developmental program of gene expression regulated at the level of translation. Protein synthesis is initiated by the assembly of multi-subunit complexes at the mRNA 5 cap structure and is recruited onto the ribosomes. There are six cap-binding proteins in Leishmania denoted LeishIF4Es1-6, and five LeishIF4G candidates. Among these, the function of LeishIF4E1 is intriguing, as it does not bind any LeishIF4G paralogs, and it is highly expressed in both parasite life forms. We examined how LeishIF4E1 phosphorylation modulates its interaction with proteins and transcripts, given that eIF4E phosphorylation in higher eukaryotes is known to regulate gene expression during malignancy. We identified three phosphorylation sites (S108, S112 and S203) and mutated them to A residues [S(108,112,203)A]. The mutated genes were transfected back into parasites for expression. Using pull-down assays, we identified the interacting proteins and associated transcripts for both the phosphorylated and non-phosphorylated LeishIF4E1 forms. The phosphorylated LeishIF4E1 pulled down proteins involved in DNA and chromatin structure, while the non-phosphorylated LeishIF4E1 interacted with proteins known to assist cells during stress and unfavorable conditions, especially gluconeogenesis. The transcript specificities differed markedly in the number of transcripts bound to both forms, shedding light on the importance of LeishIF4E1 phosphorylation. Furthermore, the phosphorylated form bound more transcripts encoding enzymes related to protein phosphorylation. We also showed that phosphorylation of LeishIF4E1 did not influence the cap-binding ability, as both the forms bind the m7GTP cap with parallel efficiencies. Our data suggest that the different cap-binding proteins in Leishmania are responsible for different processes and have a transcript-specific effect on gene expression.

microbiology↗

bioRxiv2025

A simple, fast and cost-efficient protocol for ultra-sensitive ribosome profiling

Ribosome profiling has become an essential tool for studying mRNA translation in cells with codon-level resolution. However, its widespread application remains hindered by the labour-intensive workflow, low efficiency and high costs associated with sequencing sample preparation. Here, we present a new cost-effective and ultra-sensitive library preparation method that significantly advances the applicability of ribosome profiling. By implementing bead-coupled enzymatic reactions and product purifications, our approach increases both yield and throughput while maintaining high reproducibility. Demonstrating the sensitivity of the protocol we prepared libraries from as little as 12 fmol of RNA, which expands the feasibility of ribosome profiling from minimal input samples, such as derived from small populations, stressed cells, or patient-derived specimens. Additionally, we validate the versatility of the protocol across multiple species and demonstrate its applicability for RNA-seq library preparation. Altogether, this protocol provides a highly accessible and efficient alternative to existing ribosome profiling workflows, facilitating research in previously challenging experimental contexts.

systems biology↗

bioRxiv2020

The landscape of molecular chaperones across human tissues reveals a layered architecture of core and variable chaperones

The sensitivity of the protein-folding environment to chaperone disruption can be highly tissue-specific. Yet, the organization of the chaperone system across physiological human tissues has received little attention. Here, we used human tissue RNA-sequencing profiles to analyze the expression and organization of chaperones across 29 main tissues. We found that relative to protein-coding genes, chaperones were significantly more ubiquitously and highly expressed across all tissues. Nevertheless, differential expression analysis revealed that most chaperones were up- or down-regulated in certain tissues, suggesting that they have tissue-specific roles. In agreement, chaperones that were upregulated in skeletal muscle were highly enriched in mouse myoblasts and in nematodes muscle tissue, and overlapped significantly with chaperones that are causal for muscle diseases. We also identified a distinct subset of chaperones that formed a uniformly-expressed, cross-family core group conducting basic cellular functions that was significantly more essential for cell survival. Altogether, this suggests a layered architecture of chaperones across tissues that is composed of shared core elements that are complemented by variable elements which give rise to tissue-specific functions and sensitivities, thereby contributing to the tissue-specificity of protein misfolding diseases. Significance StatementProtein misfolding diseases, such as neurodegenerative disorders and myopathies, are often manifested in a specific tissue or even a specific cell type. Enigmatically, however, they are typically caused by mutations in widely expressed proteins. Here we focused on chaperones, the main and basic components of the protein-folding machinery of cells. Computational analyses of large scale tissue transcriptomes unveils that the chaperone system is composed of core essential elements that are uniformly expressed across tissues, and of variable elements that are differentially expressed in a tissue-specific manner. This organization allows each tissue to fit the quality control system to its specific requirements and illuminates the mechanisms that underlie a tissues susceptibility to protein-misfolding diseases.

systems biology↗