Biology subjects

Ben-Zvi, A.

Publications and source records attributed to Ben-Zvi, A..

7 recordsLinked to original sources

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↗

bioRxiv2024

The landscape of cellular clearance systems across human tissues and cell types is shaped by tissue-specific proteome needs

Protein clearance is fundamental to proteome health. In eukaryotes, it is carried by two highly conserved proteolytic systems, the ubiquitin-proteasome system (UPS) and the autophagy-lysosome pathway (ALP). Despite their pivotal role, the basal organization of the human protein clearance systems across tissues and cell types remains uncharacterized. Here, we interrogated this organization using diverse omics datasets. Relative to other protein-coding genes, UPS and ALP genes were more widely expressed, encoded more housekeeping proteins, and were more essential for growth, in accordance with their fundamental roles. Most of the UPS and ALP genes were nevertheless differentially expressed across tissues, and their tissue-specific upregulation was associated with tissue-specific functions, phenotypes, and disease susceptibility. The small subset of UPS and ALP genes that was stably expressed across tissues was more highly and widely expressed and more essential for growth than other UPS and ALP genes, suggesting that it acts as a core. Lastly, we compared protein clearance to other branches of the proteostasis network. Protein clearance and folding were closely coordinated across tissues, yet both were less pivotal than protein synthesis. Taken together, we propose that the proteostasis network is organized hierarchically and is tailored to the proteome needs. This organization could contribute to and illuminate tissue-selective phenotypes.

systems biology↗

bioRxiv2024

A Tunable and Druggable Mechanism to Delay Forgetting of Olfactory Memories in C. elegans

The poet W.B Yeats wrote that "All that is personal soon rots, it must be packed in ice or salt". Here we show that in Caenorhabditis elegans nematodes, simple animals with just 302 neurons, memories are preserved on ice and in lithium salt. C. elegans nematodes can form associative memories, which are typically forgotten quickly. We discovered that when placed on ice, worms delay forgetting of specific olfactory memories by at least 8-fold. Delayed forgetting was canceled completely when the worms were gradually adapted to low temperatures, owing to a genetically-encoded program that turns acclimated worms cold-tolerant. RNA-seq, mutant analyses, and pharmacological assays revealed that regulation of membrane properties switches cold-induced delayed forgetting ON and OFF, and, remarkably, that lithium delays forgetting only in cold-sensitive but not cold-tolerant worms. We found that downregulation of the diacylglycerol pathway in the AWC sensory neurons is essential for lithium-mediated delayed forgetting, and using neuronal activity recordings located the memory trace to the downstream AIY interneurons. We suggest that the awesome genetic tractability of C. elegans might be harnessed to study the effects of lithium and cold temperatures on the brain, why it influences psychiatric disorders, and even more fundamentally how memory is stored and lost.

neuroscience↗

bioRxiv2022

Unique features of the arterial Blood-Brain Barrier

CNS vasculature differs from vascular networks of peripheral organs by its ability to tightly control selective material exchange across capillary barriers. Capillary permeability is mostly defined by unique cellular components of the endothelium. While capillaries are extensively investigated, the barrier properties of larger vessels are understudied. Here, we investigate barrier properties of CNS arterial walls. Using tracer challenges and various imaging modalities, we discovered that at the mouse cortex, the arterial barrier does not reside at the classical level of the endothelium. The arterial walls unique permeability acts bi-directionally; CSF substances travel along the glymphatic path and can penetrate from the peri-vascular space through arteriolar walls towards the lumen. We found that caveolae vesicles in arteriole endothelial and smooth-muscle cells are functional transcytosis machinery components, and that a similar mechanism is evident in the human brain. Our discoveries highlight vascular heterogeneity investigations as a potent approach to uncover new barrier mechanisms.

neuroscience↗

bioRxiv2021

Nano-scale Architecture of Blood-Brain Barrier Tight-Junctions

Tight junctions (TJs) between blood-brain barrier (BBB) endothelial cells construct a robust physical barrier, whose damage underlies BBB dysfunctions related to several neurodegenerative diseases. What makes these highly specialized BBB-TJs extremely restrictive remains unknown. Here, we use super-resolution microscopy (dSTORM) to uncover new structural and functional properties of BBB TJs. Focusing on three major components, Nano-scale resolution revealed sparse (occludin) vs. clustered (ZO1/claudin-5) molecular architecture. Developmentally, permeable TJs become first restrictive to large molecules, and only later to small molecules, with claudin-5 proteins arrangement compacting during this maturation process. Mechanistically, we reveal that ZO1 clustering is independent of claudin-5 in-vivo. In contrast to accepted knowledge, we found that in the developmental context, total levels of claudin-5 inversely correlate with TJ functionality. Our super-resolution studies provide a unique perspective of BBB TJs and open new directions for understanding TJ functionality in biological barriers, ultimately enabling restoration in disease or modulation for drug delivery.

cell 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↗

bioRxiv2019

Mutant MFN2/fzo-1 selectively removes mitochondrial DNA heteroplasmy in Caenorhabditis elegans and in Charcot-Marie-Tooth patients

Deleterious and intact mitochondrial DNA (mtDNA) mutations frequently co-exist (heteroplasmy). Such mutations likely survive and are inherited due to complementation via the intra-cellular mitochondrial network. Hence, we hypothesized that compromised mitochondrial fusion would hamper such complementation, thereby affecting heteroplasmy inheritance. To test this hypothesis, we assessed heteroplasmy levels in three Caenorhabditis elegans strains carrying different heteroplasmic mtDNA deletions ({Delta}mtDNA) in the background of mutant mitofusin. Firstly, these animals displayed severe embryonic lethality and developmental delay. Strikingly, these phenotypes were relieved during subsequent generations in association with complete {Delta}mtDNA removal. Moreover, the rates of deletion loss negatively correlated with the size of mtDNA deletions, suggesting that mitochondrial fusion is essential and sensitive to the nature of the heteroplasmic mtDNA mutations. While introducing the {Delta}mtDNA into a fzo-1;pdr-1 (PARKIN ortholog) double mutant, we observed skew in the mendelian distribution of progeny, in contrast to normal distribution in the {Delta}mtDNA;fzo-1 mutant, and severely reduced brood size. Notably, the {Delta}mtDNA was lost across generations in association with improved phenotypes. This underlines the importance of cross-talk between mitochondrial fusion and mitophagy in modulating the inheritance of mtDNA heteroplasmy. Finally, while investigating heteroplasmy patterns in three Charcot-Marie-Tooth disease type 2A pedigrees, which carry a mutated mitofusin 2, we found a single potentially deleterious heteroplasmic mutation, whose levels were selectively reduced in the patient versus healthy maternal relatives. Taken together our findings show that when mitochondrial fusion is compromised, deleterious heteroplasmic mutations cannot evade natural selection, while inherited from generation to generation.

genetics↗