Biology subjects

Banerjee, S.

Publications and source records attributed to Banerjee, S..

At least 145 records · Page 8Linked to original sources

bioRxiv2023

Role of IL-6 and IL10 immune response genes against nematode Haemonchus contortus in ovis aries- a novel report

Haemonchus contortus is one of the most deadly parasites affecting sheep industry causing heavy economic loss. In our earlier study, we have reported RIGI, an earlier established antiviral molecule and CD14 (an earlier established antibacterial molecule) to have potential role in antiparasitic immunity for the first time. In this current study, we aim to clone and sequence the IL-6 and IL10 genes in sheep (Ovis aries) and utilized bioinformatics methods to analyze and compare the functional and structural domains of peptides produced from IL6 and IL10. Furthermore, the study explored these domains in three-dimensional structures. The findings of this study provide molecular characterization of IL-6 and IL10 in sheep, which is essential for advancing our understanding of functional immune responses in this animal. We report IL6 and IL10 to have potential antiparasitic role against H. contortus for first time. The production of these molecules opens up possibilities for its potential use as recombinant proteins to manipulate the immune response. Evaluating its value in vaccine research and gaining a broader understanding of its role in immune responses becomes feasible with the availability of IL-6 and IL10. Moreover, the differential mRNA expression levels of IL-6, IL10 between healthy and diseased sheep indicate its crucial role in maintaining homeostasis and mounting immune responses. IL10 acts as receptor for H. contortus. The identification of this immune-responsive gene also offers new avenues for investigating long-term resistance to H. contortus infection in sheep.

genomics↗

bioRxiv2023

α-Synuclein emulsifies TDP-43 prion-like domain - RNA liquid droplets to promote heterotypic amyloid fibrils

Many neurodegenerative diseases including frontotemporal lobar degeneration (FTLD), Lewy body disease (LBD), multiple system atrophy (MSA), etc., show colocalized deposits of TDP-43 and -synuclein (S) aggregates. To understand whether these colocalizations are driven by specific molecular interactions between the two proteins, we previously showed that the prion-like C-terminal domain of TDP-43 (TDP-43PrLD) and S synergistically interact to form neurotoxic heterotypic amyloids in homogeneous buffer conditions. However, it remains unclear whether and how S modulates TDP-43 present within liquid droplets and biomolecular condensates called stress granules (SGs). Here, using cell culture and in vitro TDP-43PrLD - RNA liquid droplets as models along with microscopy, nanoscale spatially-resolved spectroscopy, and other biophysical analyses, we uncover the interactions of S with phase-separated droplets. We learn that S acts as a Pickering agent by forming clusters on the surface of TDP-43PrLD - RNA droplets and emulsifying them. The hardening of the droplets that follow by S aggregates on the periphery, nucleates the formation of heterotypic TDP-43PrLD amyloid fibrils with structures distinct from those derived from homogenous solutions. Together, these results reveal an intriguing property of S as a Pickering agent in interacting with SGs and unmask the hitherto unknown role of S in modulating TDP-43 proteinopathies.

biophysics↗

bioRxiv2023

Mechanical control of cell proliferation patterns in growing tissues

Cell proliferation plays a crucial role in regulating tissue homeostasis and development. However, our understanding of how cell proliferation is controlled in densely packed tissues is limited. Here we develop a computational framework to predict the patterns of cell proliferation in growing tissues, connecting single-cell behaviors and cell-cell interactions to tissue-level growth. Our model incorporates probabilistic rules governing cell growth, division, and elimination, while also taking into account their feedback with tissue mechanics. In particular, cell growth is suppressed and apoptosis is enhanced in regions of high cell density. With these rules and model parameters calibrated using experimental data, we predict how tissue confinement influences cell size and proliferation dynamics, and how single-cell physical properties influence the spatiotemporal patterns of tissue growth. Our findings indicate that mechanical feedback between tissue confinement and cell growth leads to enhanced cell proliferation at tissue boundaries, whereas cell growth in the bulk is arrested. By tuning cellular elasticity and contact inhibition of proliferation we can regulate the emergent patterns of cell proliferation, ranging from uniform growth at low contact inhibition to localized growth at higher contact inhibition. Furthermore, mechanical state of the tissue governs the dynamics of tissue growth, with cellular parameters affecting tissue pressure playing a significant role in determining the overall growth rate. Our computational study thus underscores the impact of cell mechanical properties on the spatiotemporal patterns of cell proliferation in growing tissues.

biophysics↗

bioRxiv2023

Transcriptomic analysis identifies synapse-enriched lncRNAs required for glutamatergic synapse development and fear memory consolidation.

Regulatory functions of lncRNAs in neurons have been majorly limited to the nucleus. The identity of synaptic lncRNAs and their functional roles associated with synapse development and plasticity are poorly understood. Transcriptomic analysis from synaptoneurosomes identified 94 synapse-enriched lncRNAs from the mouse hippocampus. We find Pvt1 to be a specific regulator of excitatory, not inhibitory, synapse development. Synapse-specific loss of Pvt1 regulates synaptic activity and the downregulation of mRNAs pertinent to synapse development. We also report a synapse-centric role for an uncharacterized lncRNA; 2410006H16Rik (SynLAMP); in translation and memory formation. SynLAMP demonstrates enhanced localization to the synapse following fear conditioning and regulates dendritic translation by sequestering the translation repressor FUS; acting as a molecular decoy. Synapse-specific knockdown of SynLAMP inhibits the localised, activity-dependent translation of CamK2a, a FUS target. SynLAMP RNAi occludes fear-memory formation. Comprehensively, our study highlights that de novo activity of lncRNAs are involved in diverse synaptic functions.

neuroscience↗

bioRxiv2023

Patterns of recombination in snakes reveal a tug of war between PRDM9 and promoter-like features

In vertebrates, there are two known mechanisms by which meiotic recombination is directed to the genome: in humans, mice, and other mammals, recombination occurs almost exclusively where the protein PRDM9 binds, while in species lacking an intact PRDM9, such as birds and canids, recombination rates are elevated near promoter-like features. To test if PRDM9 also directs recombination in non-mammalian vertebrates, we focused on an exemplar species, the corn snake (Pantherophis guttatus). Unlike birds, this species possesses a single, intact PRDM9 ortholog. By inferring historical recombination rates along the genome from patterns of linkage disequilibrium and identifying crossovers in pedigrees, we found that PRDM9 specifies the location of recombination events outside of mammals. However, we also detected an independent effect of promoter-like features on recombination, which is more pronounced on macrothan microchromosomes. Thus, our findings reveal that the uses of PRDM9 and promoter-like features are not mutually-exclusive, and instead reflect a tug of war, which varies in strength along the genome and is more lopsided in some species than others. One sentence summaryWhile the localization of meiotic recombination in vertebrates was previously thought to occur using one of two distinct mechanisms, our analysis of recombination in corn snakes reveals that they and likely other vertebrates use both of these mechanisms.

evolutionary biology↗

bioRxiv2023

Differences in Hepatocellular Iron Metabolism Underlie Sexual Dimorphism in Hepatocyte Ferroptosis

Males show higher incidence and severity than females in hepatic injury and many liver diseases, but the mechanisms are not well understood. Ferroptosis, an iron-mediated lipid peroxidation-dependent death, plays an important role in the pathogenesis of liver diseases. We determined whether hepatocyte ferroptosis displays gender difference, accounting for sexual dimorphism in liver diseases. Compared to female hepatocytes, male hepatocytes were much more vulnerable to ferroptosis by iron and pharmacological inducers including RSL3 and iFSP1. Male but not female hepatocytes exhibited significant increases in mitochondrial Fe2+ and mitochondrial ROS (mtROS) contents. Female hepatocytes showed a lower expression of iron importer transferrin receptor 1 (TfR1) and mitochondrial iron importer mitoferrin 1 (Mfrn1), but a higher expression of iron storage protein ferritin heavy chain 1 (FTH1). It is well known that TfR1 expression is positively correlated with ferroptosis. Herein, we showed that silencing FTH1 enhanced while knockdown of Mfrn1 decreased ferroptosis in HepG2 cells. Removing female hormones by ovariectomy (OVX) did not dampen but rather enhanced hepatocyte resistance to ferroptosis. Mechanistically, OVX potentiated the decrease in TfR1 and increase in FTH1 expression. OVX also increased FSP1 expression in ERK-dependent manner. Elevation in FSP1 suppressed mitochondrial Fe2+ accumulation and mtROS production, constituting a novel mechanism of FSP1-mediated inhibition of ferroptosis. In conclusion, differences in hepatocellular iron handling between male and female account, at least in part, for sexual dimorphism in induced ferroptosis of the hepatocytes.

cell biology↗

bioRxiv2023

The molecular prognostic score, a classifier for risk stratification of high-grade serous ovarian cancer

The clinicopathological parameters such as residual tumor, grade, FIGO score are often used to predict the survival of ovarian cancer patients, but the 5-year survival of high grade serous ovarian cancer (HGSOC) still remains around 30%. In recent years, a gene expression based molecular prognostic score (mPS) was developed that showed improved prognosis in several cancers including ovarian cancer. The feature extraction using LASSO-Cox regression was applied on the training data with 10-fold cross validation to obtain 20 predictor genes along with the coefficients to derive mPS. The mPS based prognosis of HGSOC patients was validated using the log-rank test and receiver operator characteristic curve. The AUC of 20 gene-based mPS in predicting the 5-year overall survival was around 0.7 in both the training (n=491) and test datasets (n=491). It was also validated across HGSOC patients (n=7542), data collected from the Ovarian Tumor Tissue Analysis (OTTA) consortium. The mPS showed significant impact (adjusted HR = 6.1, 95% CI of HR= 3.65-10.3; p <0.001) on prognosis of HGSOC. The performance of mPS for the prognosis of survival of HGSOC was substantially better than conventional parameters: FIGO (adjusted HR=1.1, 95% CI=0.97-1.2, p=0.121), residual disease (adjusted HR=1.3, 95% CI= 1.13-1.4, p<0.001), and age (adjusted HR=1.2, 95% CI= 0.98-1.6, p=0.08). It was found that focal-adhesion, Wnt and Notch signaling pathways were significantly (p<0.001) upregulated, whereas antigen processing and presentation (p<0.001) was downregulated in high risk HGSOC cohorts based on mPS stratification. The molecular prognostic score derived from 20-gene signature is found to be the novel robust prognostic marker of HGSOC. It could potentially be harnessed in clinical settings to determine the overall survival of ovarian cancer. The high risk HGSOC patients based on mPS stratification could be benefited from alternative therapies targeting Wnt/ Notch signaling pathways and also immune evasion. Author summaryThe 20-gene signature based molecular prognostic score (mPS) was found to be associated with risk stratification and hence, predicting the overall survival time of HGSOCs. It was applicable in all training HGSOC datasets and across RNA sequencing platforms that also includes the previous reported studies in HGSOC cohorts (Millstein et al., 2020; Talhouk et al., 2020). The 20-gene signature based mPS for the prognosis of overall survival of HGSOC outperformed conventional parameters: age, residual disease and FIGO score. The high or increased risk group of HGSOC based on our mPS stratification was found to have dysregulated pathways of Wnt, Notch, Akt signaling, and antigen presentation. Thus, treatments targeting these pathways might be beneficial for high risk HGSOC and hence anticipated to improve the over-all survival of HGSOC.

genomics↗

bioRxiv2023

Development and Optimisation of in vitro Sonodynamic Therapy for Glioblastoma

BackgroundSonodynamic therapy (SDT) is currently on critical path for glioblastoma therapeutics. However, the molecular mechanisms underlying the therapeutic functions of SDT remain enigmatic due to the lack of intricately optimised instrumentation capable of modulating SDT delivery in vitro. We established and validated an automated in vitro SDT system and assessed its SDT efficacy. MethodsAn automated in vitro SDT system was established and validated to allow the application and mapping of focused ultrasound fields under varied acoustic exposure conditions and setup configurations. Ultrasound field simulations were performed to assess the acoustic energy exposure. Systematic in vitro investigations were performed to optimise ultrasound frequency, intensity, plate base material, thermal effect, and the integration of live cells. ResultsIn the presence of 5-ALA, focused ultrasound induces apoptotic cell death in primary patient-derived glioma cells with concurrent upregulation of intracellular reactive oxygen species. Intriguingly, primary glioma stem neurospheres also exhibit remarkably reduced 3D growth upon SDT exposure. Further, ultrasound field simulations performed established acoustic field distribution and the impact of acoustic standing waves within the well-plates. ConclusionsThe optimised in vitro SDT system and associated ultrasound field simulations establish the basis for further understanding of SDT and its therapeutic potentials in cancer.

bioengineering↗

bioRxiv2023

Catalytic growth in a shared enzyme pool ensures robust control of centrosome size

Accurate regulation of centrosome size is essential for ensuring error-free cell division, and dysregulation of centrosome size has been linked to various pathologies, including developmental defects and cancer. While a universally accepted model for centrosome size regulation is lacking, prior theoretical and experimental works suggest a centrosome growth model involving autocatalytic assembly of the pericentriolar material. Here we show that the autocatalytic assembly model fails to explain the attainment of equal centrosome sizes, which is crucial for error-free cell division. Incorporating latest experimental findings into the molecular mechanisms governing centrosome assembly, we introduce a new quantitative theory for centrosome growth involving catalytic assembly within a shared pool of enzymes. Our model successfully achieves robust size equality between maturing centrosome pairs, mirroring cooperative growth dynamics observed in experiments. To validate our theoretical predictions, we compare them with available experimental data and demonstrate the broad applicability of the catalytic growth model across different organisms, which exhibit distinct growth dynamics and size scaling characteristics.

cell biology↗

bioRxiv2023

Biochemical, biomarker, and behavioral characterization of the GrnR493X mouse model of frontotemporal dementia

Heterozygous loss-of-function mutations in the progranulin gene (GRN) are a major cause of frontotemporal dementia due to progranulin haploinsufficiency; complete deficiency of progranulin causes neuronal ceroid lipofuscinosis. Several progranulin-deficient mouse models have been generated, including both knockout mice and knockin mice harboring a common patient mutation (R493X). However, the GrnR493X mouse model has not been characterized completely. Additionally, while homozygous GrnR493X and Grn knockout mice have been extensively studied, data from heterozygous mice is still limited. Here, we performed more in-depth characterization of heterozygous and homozygous GrnR493X knockin mice, which includes biochemical assessments, behavioral studies, and analysis of fluid biomarkers. In the brains of homozygous GrnR493X mice, we found increased phosphorylated TDP-43 along with increased expression of lysosomal genes, markers of microgliosis and astrogliosis, pro-inflammatory cytokines, and complement factors. Heterozygous GrnR493X mice did not have increased TDP-43 phosphorylation but did exhibit limited increases in lysosomal and inflammatory gene expression. Behavioral studies found social and emotional deficits in GrnR493X mice that mirror those observed in Grn knockout mouse models, as well as impairment in memory and executive function. Overall, the GrnR493X knockin mouse model closely phenocopies Grn knockout models. Lastly, in contrast to homozygous knockin mice, heterozygous GrnR493X mice do not have elevated levels of fluid biomarkers previously identified in humans, including neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) in both plasma and CSF. These results may help to inform pre-clinical studies that use this Grn knockin mouse model and other Grn knockout models.

neuroscience↗

bioRxiv2023

dsSurvival 2.0: Privacy enhancing survival curves for survival models in the federated DataSHIELD analysis system

ObjectiveSurvival models are used extensively in biomedical sciences, where they allow the investigation of the effect of exposures on health outcomes. It is desirable to use diverse data sets in survival analyses, because this offers increased statistical power and generalisability of results. However, there are often challenges with bringing data together in one location or following an analysis plan and sharing results. DataSHIELD is an analysis platform that helps users to overcome these ethical, governance and process difficulties. It allows users to analyse data remotely, using functions that are built to restrict access to the detailed data items (federated analysis). Previous works have provided survival modelling functionality in DataSHIELD (dsSurvival package), but there is a requirement to provide functions that offer privacy enhancing survival curves that retain useful information. ResultsWe introduce an enhanced version of the dsSurvival package which offers privacy enhancing survival curves for DataSHIELD. Different methods for enhancing privacy were evaluated for their effec-tiveness in enhancing privacy while maintaining utility. We demonstrated how our selected method could enhance privacy in different scenarios using real survival data. The details of how DataSHIELD can be used to generate survival curves can be found in the associated tutorial.

bioinformatics↗

bioRxiv2023

Unveiling the Domain-Specific and RAS Isoform-Specific Details of BRAF Regulation

BRAF is a key member in the MAPK signaling pathway essential for cell growth, proliferation, and differentiation. Dysregulation or mutation of BRAF is often the underlying cause of various types of cancer. RAS, a small GTPase protein that acts upstream of BRAF, has been identified as a driver of up to one-third of all cancers. When BRAF interacts with RAS via the RAS binding domain (RBD) and membrane recruitment, BRAF undergoes a conformational change from an inactive, autoinhibited monomer to an active dimer and subsequently phosphorylates MEK to propagate the signal. Despite the central role of BRAF in cellular signaling, the exact order and magnitude of its activation steps has yet to be confirmed experimentally. By studying the inter- and intramolecular interactions of BRAF, we unveil the domain-specific and isoform-specific details of BRAF regulation. We employed pulldown assays, open surface plasmon resonance (OpenSPR), and hydrogen-deuterium exchange mass spectrometry (HDX-MS) to investigate the roles of the regulatory regions in BRAF activation and autoinhibition. Our results demonstrate that the BRAF specific region (BSR) and cysteine rich domain (CRD) play a crucial role in regulating the activity of BRAF. Moreover, we quantified the autoinhibitory binding affinities between the N-terminal domains and the kinase domain (KD) of BRAF and revealed the individual roles of the BRAF regulatory domains. Additionally, our findings provide evidence that the BSR negatively regulates BRAF activation in a RAS isoform-specific manner. Our findings also indicate that oncogenic BRAF-KDD594G mutant has a lower affinity for the regulatory domains, implicating that pathogenic BRAF acts through decreased propensity for autoinhibition. Collectively, our study provides valuable insights into the activation mechanism of BRAF kinase and may help to guide the development of new therapeutic strategies for cancer treatment.

biochemistry↗

bioRxiv2023

Intermediate antiparallel beta structure in amyloid plaques revealed by infrared spectroscopic imaging

Aggregation of amyloid beta (A{beta}) peptides into extracellular plaques is a hallmark of the molecular pathology of Alzheimers disease (AD). Amyloid aggregates have been extensively studied in-vitro, and it is well known that mature amyloid fibrils contain an ordered parallel {beta} structure. The structural evolution from unaggregated peptide to fibrils can be mediated through intermediate structures that deviate significantly from mature fibrils, such as antiparallel {beta}-sheets. However, it is currently unknown if these intermediate structures exist in plaques, which limits the translation of findings from in-vitro structural characterizations of amyloid aggregates to AD. This arises from the inability to extend common structural biology techniques to ex-vivo tissue measurements. Here we report the use of infrared (IR) imaging, wherein we can spatially localize plaques and probe their protein structural distributions with the molecular sensitivity of IR spectroscopy. Analyzing individual plaques in AD tissues, we demonstrate that fibrillar amyloid plaques exhibit antiparallel {beta}-sheet signatures, thus providing a direct connection between in-vitro structures and amyloid aggregates in AD brain. We further validate results with IR imaging of in-vitro aggregates and show that antiparallel {beta}-sheet structure is a distinct structural facet of amyloid fibrils.

biophysics↗

bioRxiv2023

A bioorthogonal antibody-based chemically-induced-dimerization switch for therapeutic application

We present the Indinavir Ligand Induced Transient Engagement switch (IDV LITE Switch), a fully synthetic Chemically Induced Dimerization (CID) system wherein two humanized antibody fragments are heterodimerized by the antiviral drug indinavir. The IDV LITE Switch represents the first CID system made from fully humanized protein components and dimerized by a clinically approved small molecule drug lacking a mammalian target, making it an ideal bioorthogonal molecular switch for application in small-molecule controlled therapeutics.

synthetic biology↗

bioRxiv2023

A critical role for PLCG1 in RAS activation by BCR-ABL1 and FLT3-ITD

Myeloid leukemias are frequently associated with pathologically activating mutations in tyrosine kinases [BCR-ABL1 in chronic myeloid leukemia (CML); FLT3 juxtamembrane internal tandem duplication (ITD) mutations, FLT3 and KIT activation loop mutations in acute myeloid leukemia (AML)]. Mutations in these kinases activate RAS, which initiates multiple downstream signaling pathways that regulate cell proliferation, differentiation, and apoptosis. The mechanisms whereby RAS is activated by these kinases is incompletely understood, and a better understanding of the molecular mediators involved in RAS activation may uncover new therapeutic strategies. Here we identify a biologically and therapeutically important novel mechanism whereby BCR-ABL1 and FLT3-ITD activate the critical downstream effector RAS in part through phospholipase C gamma-1 (PLCG1). PLCG1 knockout decreases proliferation of CML and FLT3-ITD-expressing AML cells, reduces RAS nucleotide exchange factor activity, and increases sensitivity of CML cells to BCR-ABL1 tyrosine kinase inhibitors (TKIs). Collectively, these studies suggest that PLCG1 inhibition may augment clinical responses to BCR-ABL1 and FLT3 TKIs in CML and AML.

cancer biology↗

bioRxiv2023

Plant cellulose synthase membrane protein isolation directly from Pichia pastoris protoplasts, liposome reconstitution, and its enzymatic characterization

The most abundant renewable biopolymer on earth, viz., cellulose, acts as carbon storage reserve in plant and microbial cell walls that could potentially be converted into biofuels or other valuable bioproducts. Cellulose is synthesized by a plant cell membrane-integrated processive glycosyltransferase (GT) called cellulose synthase (CesA). Since only a few of these plant CesAs have been purified and characterized to date, there are huge gaps in our mechanistic understanding of these enzymes. Furthermore, the coordination between different CesAs involved in primary and secondary cell wall formation is yet to be unveiled. The biochemistry and structural biology studies of CesAs are currently hampered by challenges associated with their expression and extraction at high yields. To aid in understanding CesA reaction mechanisms and to provide a more efficient CesA extraction method, two putative plant CesAs - PpCesA5 from Physcomitrella patens and PttCesA8 from Populus tremula x tremuloides that are involved in primary and secondary cell wall formation in plants were expressed using Pichia pastoris as an expression host. We developed a protoplast-based membrane protein extraction approach to directly isolate both these membrane-bound enzymes for purification, as detected by immunoblotting and mass spectrometry-based analyses. Our method results in a higher purified protein yield by 3-4-fold than the standard cell homogenization protocol. Our purified CesAs were reconstituted into liposomes to yield active enzymes that gave similar biochemical characteristics (e.g., substrate utilization and cofactor requirements, no primer needed to initiate polymerization reaction) as enzymes isolated using the standard protocol. This method resulted in reconstituted CesA5 and CesA8 with similar Michaelis-Menten kinetic constants, Km = 167 M, 108 M and Vmax = 7.88x10-5 mol/min, 4.31x10-5 mol/min, respectively, in concurrence with the previous studies. Taken together, these results suggest that CesAs involved in primary and secondary cell wall formation can be expressed and purified using a simple and more efficient extraction method. This could potentially help unravel the mechanism of native and engineered cellulose synthase complexes involved in plant cell wall biosynthesis.

bioengineering↗

bioRxiv2023

Intermediate antiparallel fibrils in Aβ40 Dutch mutant aggregation: nanoscale insights from AFM-IR

Cerebral Amyloid Angiopathy (CAA), which involves amyloid deposition in blood vessels leading to fatal cerebral hemorrhage and recurring strokes, is present in the majority Alzheimers disease cases. Familial mutations in the amyloid {beta} peptide is correlated to higher risks of CAA, and are mostly comprised of mutations at residues 22 and 23. While the structure of the wild type A{beta} peptide has been investigated in great detail, less is known about the structure of mutants involved in CAA and evolutions thereof. This is particularly true for mutations at residue 22, for which detailed molecular structures, as typically determined from Nuclear Magnetic Resonance (NMR) spectroscopy or electron microscopy, do not exist. In this report, we have used nanoscale infrared (IR) spectroscopy augmented with Atomic Force Microscopy (AFM-IR) to investigate structural evolution of the A{beta} Dutch mutant (E22Q) at the single aggregate level. We show that that in the oligomeric stage, the structural ensemble is distinctly bimodal, with the two subtypes differing with respect to population of parallel {beta}-sheets. Fibrils on the other hand are structurally homogeneous, with early-stage fibrils distinctly anti parallel in character, which develop parallel {beta}-sheets upon maturation. Furthermore, the antiparallel structure is found to be a persistent feature across different stages of aggregation.

biophysics↗

bioRxiv2023

Force-regulated chaperone activity of BiP/ERdj3 is opposite to their homologs DnaK/DnaJ: explained by strain energy

Polypeptide chains experiences mechanical tension while translocating through cellular tunnel. In this scenario, interaction of tunnel-associated chaperones with the emerging polypeptide occurs under force; however, this force-regulated chaperone behaviour is not fully understood. We studied the mechanical chaperone activity of two tunnel-associated chaperones BiP and ERdj3 both in the absence and presence of force; and compared to their respective cytoplasmic homologs DnaK and DnaJ. We found that BiP/ERdj3 shows strong foldase activity under force; whereas their cytoplasmic homolog DnaK/DnaJ behave as holdase. Importantly, these tunnel-associated chaperones (BiP/ERdj3) revert to holdase in the absence of force, suggesting that mechanical chaperone activity differs depending on the presence or absence of force. This tunnel-associated chaperone-driven folding event generates additional mechanical energy of up to 54 zJ that could help protein translocation. The mechanical-chaperone behaviour can be explained by strain theory: chaperones with higher intrinsic deformability function as mechanical foldase (BiP, ERdj3), while chaperones with lower intrinsic deformability act as holdase (DnaK and DnaJ). Our study thus unveils the underlying mechanism of mechanically regulated chaperoning activity and provides a novel mechanism of co-translocational protein folding. SignificanceThe mechanical-activity of chaperones, located at the edge of a tunnel, could be different from their cytoplasmic homologs. Translocating substrates within the tunnel are known to experience mechanical constraints, whereas the cytosolic substrates interact with the chaperones in the absence of force. To understand this phenomenon, we investigated two tunnel-associated chaperones BiP/ERdj3 and their cytosolic homologs-DnaK/DnaJ. We observed that BiP/ERdj3 possess strong foldase activity while their substrates are under force; whereas DnaK/DnaJ possess holdase function. Notably all these chaperones function as holdase in the absence of force, which suggest that mechanical chaperone activity is different with and without force. We explained this mechanical behaviour using strain theory, providing a physical mechanism of chaperone-assisted co-translocational protein folding.

biophysics↗