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BioRxiv : the Preprint Server For... Jun 2024KRAS is frequently mutated in cancer, contributing to 20% of all human cancer especially pancreatic, colorectal and lung cancer. Signaling of the constitutively active...
KRAS is frequently mutated in cancer, contributing to 20% of all human cancer especially pancreatic, colorectal and lung cancer. Signaling of the constitutively active KRAS oncogenic mutants is mostly compartmentalized to proteolipid nanoclusters on the plasma membrane (PM). Signaling nanoclusters of many KRAS mutants selectively enrich phosphatidylserine (PS) lipids with unsaturated acyl chains, but not the fully saturated PS species. Thus, remodeling PS acyl chains may suppress KRAS oncogenesis. Lysophosphatidylcholine acyltransferases (LPCATs) remodel acyl chains of phospholipids, with LPCAT1 preferentially generating the fully saturated lipids. Here, we show that stable expression of LPCAT1 depletes major PS species with unsaturated sn-2 chains while decreasing minor phosphatidylcholine (PC) species with the corresponding acyl chains. LPCAT1 expression more effectively disrupts the nanoclustering of oncogenic GFP-KRAS, which is restored by acute addback of exogenous unsaturated PS. LPCAT1 expression compromises signaling and oncogenic activities of the KRAS-dependent pancreatic tumor lines. LPCAT1 expression sensitizes human pancreatic tumor MiaPaCa-2 cells to KRAS specific inhibitor, Sotorasib. Statistical analyses of patient data further reveal that pancreatic cancer patients with KRAS mutations express less LPCAT1. Higher LPCAT1 expression also improves survival probability of pancreatic and lung adenocarcinoma patients with KRAS mutations. Thus, PS acyl chain remodeling selectively suppresses KRAS oncogenesis.
PubMed: 38853864
DOI: 10.1101/2024.05.30.596653 -
Journal of Photochemistry and... Sep 2023In plants, the major light-harvesting antenna complex (LHCII) is vital for both light harvesting and photoprotection in photosystem II. Previously, we proposed that the...
In plants, the major light-harvesting antenna complex (LHCII) is vital for both light harvesting and photoprotection in photosystem II. Previously, we proposed that the thylakoid membrane itself could switch LHCII into the photoprotective state, qE, via a process known as hydrophobic mismatch. The decrease in the membrane thickness that followed the formation of ΔpH was a key fact that prompted this idea. To test this, we made proteoliposomes from lipids with altered acyl chain length (ACL). Here, we show that ACL regulates the average chlorophyll fluorescence lifetime of LHCII. For liposomes made of lipids with an ACL of 18 carbons, the lifetime was ∼2 ns, like that for the thylakoid membrane. Furthermore, LHCII appears to be quenched in proteoliposomes with an ACL both shorter and longer than 18 carbons. The proteoliposomes made of short ACL lipids display structural heterogeneity revealing two quenched conformations of LHCII, each having characteristic 77 K fluorescence spectra. One conformation spectrally resembles isolated LHCII aggregates, whilst the other resembles LHCII immobilized in polyacrylamide gels. Overall, the decrease in the ACL appears to produce quenched conformations of LHCII, which renders plausible the idea that the trigger of qE is the hydrophobic mismatch.
Topics: Light-Harvesting Protein Complexes; Thylakoids; Photosystem II Protein Complex; Proteolipids; Chlorophyll
PubMed: 37531665
DOI: 10.1016/j.jphotobiol.2023.112758 -
Comparative Biochemistry and... Sep 2024Regional endothermy is the ability of an animal to elevate the temperature of specific regions of the body above that of the surrounding environment and has evolved...
Relative sarcolipin (SLN) and sarcoplasmic reticulum Ca ATPase (SERCA1) transcripts levels in closely related endothermic and ectothermic scombrid fishes: Implications for molecular basis of futile calcium cycle non-shivering thermogenesis (NST).
Regional endothermy is the ability of an animal to elevate the temperature of specific regions of the body above that of the surrounding environment and has evolved independently among several fish lineages. Sarcolipin (SLN) is a small transmembrane protein that uncouples the sarcoplasmic reticulum calcium ATPase pump (SERCA1b) resulting in futile Ca cycling and is thought to play a role in non-shivering thermogenesis (NST) in cold-challenged mammals and possibly some fishes. This study investigated the relative expression of sln and serca1 transcripts in three regionally-endothermic fishes (the skipjack, Katsuwonus pelamis, and yellowfin tuna, Thunnus albacares, both of which elevate the temperatures of their slow-twitch red skeletal muscle (RM) and extraocular muscles (EM), as well as the cranial endothermic swordfish, Xiphias gladius), and closely related ectothermic scombrids (the Eastern Pacific bonito, Sarda chiliensis, and Pacific chub mackerel, Scomber japonicus). Using Reverse Transcription quantitative PCR (RT-qPCR) and species-specific primers, relative sln expression trended higher in both the RM and EM for all four scombrid species compared to white muscle. In addition, relative serca1 expression was found to be higher in RM of skipjack and yellowfin tuna in comparison to white muscle. However, neither sln nor serca1 transcripts were higher in swordfish RM, EM or cranial heater tissue in comparison to white muscle. A key phosphorylation site in sarcolipin, threonine 5, is conserved in the swordfish, but is mutated to alanine or valine in tunas and the endothermic smalleye Pacific opah, Lampris incognitus, which should result in increased uncoupling of the SERCA pump. Our results support the role of potential SLN-NST in endothermic tunas and the lack thereof for swordfish.
Topics: Animals; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Proteolipids; Muscle Proteins; Thermogenesis; Calcium; Fish Proteins; Muscle, Skeletal; RNA, Messenger; Perciformes; Tuna
PubMed: 38782254
DOI: 10.1016/j.cbpa.2024.111667 -
Bioscience Reports Feb 2024Light-harvesting 2 (LH2) and reaction-centre light-harvesting 1 (RC-LH1) complexes purified from the photosynthetic bacterium Rhodobacter (Rba.) sphaeroides were...
Light-harvesting 2 (LH2) and reaction-centre light-harvesting 1 (RC-LH1) complexes purified from the photosynthetic bacterium Rhodobacter (Rba.) sphaeroides were reconstituted into proteoliposomes either separately, or together at three different LH2:RC-LH1 ratios, for excitation energy transfer studies. Atomic force microscopy (AFM) was used to investigate the distribution and association of the complexes within the proteoliposome membranes. Absorption and fluorescence emission spectra were similar for LH2 complexes in detergent and liposomes, indicating that reconstitution retains the structural and optical properties of the LH2 complexes. Analysis of fluorescence emission shows that when LH2 forms an extensive series of contacts with other such complexes, fluorescence is quenched by 52.6 ± 1.4%. In mixed proteoliposomes, specific excitation of carotenoids in LH2 donor complexes resulted in emission of fluorescence from acceptor RC-LH1 complexes engineered to assemble with no carotenoids. Extents of energy transfer were measured by fluorescence lifetime microscopy; the 0.72 ± 0.08 ns lifetime in LH2-only membranes decreases to 0.43 ± 0.04 ns with a ratio of 2:1 LH2 to RC-LH1, and to 0.35 ± 0.05 ns for a 1:1 ratio, corresponding to energy transfer efficiencies of 40 ± 14% and 51 ± 18%, respectively. No further improvement is seen with a 0.5:1 LH2 to RC-LH1 ratio. Thus, LH2 and RC-LH1 complexes perform their light harvesting and energy transfer roles when reconstituted into proteoliposomes, providing a way to integrate native, non-native, engineered and de novo designed light-harvesting complexes into functional photosynthetic systems.
Topics: Rhodobacter sphaeroides; Cytoplasm; Photosynthesis; Energy Transfer; Bacterial Proteins; Proteolipids
PubMed: 38227291
DOI: 10.1042/BSR20231302 -
Clinical Epigenetics Mar 2024MAL (T-lymphocyte maturation-associated protein) is highly downregulated in most cancers, including cervical cancer (CaCx), attributable to promoter hypermethylation....
MAL expression downregulation through suppressive H3K27me3 marks at the promoter in HPV16-related cervical cancers is prognostically relevant and manifested by the interplay of novel MAL antisense long noncoding RNA AC103563.8, E7 oncoprotein and EZH2.
BACKGROUND
MAL (T-lymphocyte maturation-associated protein) is highly downregulated in most cancers, including cervical cancer (CaCx), attributable to promoter hypermethylation. Long noncoding RNA genes (lncGs) play pivotal roles in CaCx pathogenesis, by interacting with human papillomavirus (HPV)-encoded oncoproteins, and epigenetically regulating coding gene expression. Hence, we attempted to decipher the impact and underlying mechanisms of MAL downregulation in HPV16-related CaCx pathogenesis, by interrogating the interactive roles of MAL antisense lncRNA AC103563.8, E7 oncoprotein and PRC2 complex protein, EZH2.
RESULTS
Employing strand-specific RNA-sequencing, we confirmed the downregulated expression of MAL in association with poor overall survival of CaCx patients bearing HPV16, along with its antisense long noncoding RNA (lncRNA) AC103563.8. The strength of positive correlation between MAL and AC103563.8 was significantly high among patients compared to normal individuals. While downregulated expression of MAL was significantly associated with poor overall survival of CaCx patients bearing HPV16, AC103563.8 did not reveal any such association. We confirmed the enrichment of chromatin suppressive mark, H3K27me3 at MAL promoter, using ChIP-qPCR in HPV16-positive SiHa cells. Subsequent E7 knockdown in such cells significantly increased MAL expression, concomitant with decreased EZH2 expression and H3K27me3 marks at MAL promoter. In silico analysis revealed that both E7 and EZH2 bear the potential of interacting with AC103563.8, at the same binding domain. RNA immunoprecipitation with anti-EZH2 and anti-E7 antibodies, respectively, and subsequent quantitative PCR analysis in E7-silenced and unperturbed SiHa cells confirmed the interaction of AC103563.8 with EZH2 and E7, respectively. Apparently, AC103563.8 seems to preclude EZH2 and bind with E7, failing to block EZH2 function in patients. Thereby, enhanced EZH2 expression in the presence of E7 could potentially inactivate the MAL promoter through H3K27me3 marks, corroborating our previous results of MAL expression downregulation in patients.
CONCLUSION
AC103563.8-E7-EZH2 axis, therefore, appears to crucially regulate the expression of MAL, through chromatin inactivation in HPV16-CaCx pathogenesis, warranting therapeutic strategy development.
Topics: Female; Humans; Chromatin; DNA Methylation; Down-Regulation; Enhancer of Zeste Homolog 2 Protein; Histones; Human papillomavirus 16; Oncogene Proteins, Viral; Papillomavirus E7 Proteins; RNA, Long Noncoding; Uterine Cervical Neoplasms; Myelin and Lymphocyte-Associated Proteolipid Proteins
PubMed: 38461243
DOI: 10.1186/s13148-024-01651-9 -
Genes Mar 2024Microribonucleic acids (miRNAs) comprising miR-23a/b clusters, specifically miR-23a and miR-27a, are recognized for their divergent roles in myelination within the...
Microribonucleic acids (miRNAs) comprising miR-23a/b clusters, specifically miR-23a and miR-27a, are recognized for their divergent roles in myelination within the central nervous system. However, cluster-specific miRNA functions remain controversial as miRNAs within the same cluster have been suggested to function complementarily. This study aims to clarify the role of miR-23a/b clusters in myelination using mice with a miR-23a/b cluster deletion (KO mice), specifically in myelin expressing proteolipid protein (PLP). Inducible conditional KO mice were generated by crossing miR-23a/b cluster mice with mice; the offspring were injected with tamoxifen at 10 days or 10 weeks of age to induce a myelin-specific miR-23a/b cluster deletion. Evaluation was performed at 10 weeks or 12 months of age and compared with control mice that were not treated with tamoxifen. KO mice exhibit impaired motor function and hypoplastic myelin sheaths in the brain and spinal cord at 10 weeks and 12 months of age. Simultaneously, significant decreases in myelin basic protein (MBP) and PLP expression occur in KO mice. The percentages of oligodendrocyte precursors and mature oligodendrocytes are consistent between the KO and control mice. However, the proportion of oligodendrocytes expressing MBP is significantly lower in KO mice. Moreover, changes in protein expression occur in KO mice, with increased leucine zipper-like transcriptional regulator 1 expression, decreased R-RAS expression, and decreased phosphorylation of extracellular signal-regulated kinases. These findings highlight the significant influence of miR-23a/b clusters on myelination during postnatal growth and aging.
Topics: Animals; MicroRNAs; Mice; Myelin Sheath; Aging; Central Nervous System; Mice, Knockout; Myelin Proteolipid Protein; Spinal Cord; Myelin Basic Protein; Oligodendroglia; Brain
PubMed: 38674338
DOI: 10.3390/genes15040402 -
Cell Reports May 2024Satellite glial cells (SGCs) of dorsal root ganglia (DRGs) are activated in a variety of chronic pain conditions; however, their mediation roles in pain remain elusive....
Satellite glial cells (SGCs) of dorsal root ganglia (DRGs) are activated in a variety of chronic pain conditions; however, their mediation roles in pain remain elusive. Here, we take advantage of proteolipid protein (PLP)/creER-driven recombination in the periphery mainly occurring in SGCs of DRGs to assess the role of SGCs in the regulation of chronic mechanical hypersensitivity and pain-like responses in two organs, the distal colon and hindpaw, to test generality. We show that PLP/creER-driven hM3Dq activation increases, and PLP/creER-driven TrkB.T1 deletion attenuates, colon and hindpaw chronic mechanical hypersensitivity, positively associating with calcitonin gene-related peptide (CGRP) expression in DRGs and phospho-cAMP response element-binding protein (CREB) expression in the dorsal horn of the spinal cord. Activation of Plp1 DRG cells also increases the number of small DRG neurons expressing Piezo2 and acquiring mechanosensitivity and leads to peripheral organ neurogenic inflammation. These findings unravel a role and mechanism of Plp1 cells, mainly SGCs, in the facilitation of chronic mechanical pain and suggest therapeutic targets for pain mitigation.
Topics: Animals; Ganglia, Spinal; Chronic Pain; Up-Regulation; Neurons; Mice; Ion Channels; Colon; Male; Hyperalgesia; Myelin Proteolipid Protein; Neuroglia
PubMed: 38743566
DOI: 10.1016/j.celrep.2024.114230 -
BMJ Open Jun 2024WHO recommends human papillomavirus (HPV) testing for cervical screening, with triage of high-risk HPV (hrHPV) positive women. However, there are limitations to... (Observational Study)
Observational Study
Performance of and methylation as triage markers for early detection of cervical cancer in self-collected and clinician-collected samples: an exploratory observational study in Papua New Guinea.
OBJECTIVE
WHO recommends human papillomavirus (HPV) testing for cervical screening, with triage of high-risk HPV (hrHPV) positive women. However, there are limitations to effective triage for low-resource, high-burden settings, such as Papua New Guinea. In this exploratory study, we assessed the performance of host methylation as triage tools for predicting high-grade squamous intraepithelial lesions (HSIL) in self-collected and clinician-collected samples.
DESIGN
Exploratory observational study.
SETTING
Provincial hospital, same-day cervical screen-and-treat trial, Papua New Guinea.
PARTICIPANTS
44 hrHPV+women, with paired self/clinician-collected samples (4 squamous cell carcinomas (SCC), 19 HSIL, 4 low-grade squamous intraepithelial lesions, 17 normal).
PRIMARY AND SECONDARY OUTCOME MEASURES
Methylation levels of and analysed by methylation-specific PCRs against the clinical endpoint of HSIL or SCC (HSIL+) measured using liquid-based-cytology/p16-Ki67 stain.
RESULTS
In clinician-collected samples, and methylation levels were significantly higher with increasing grade of disease (p=0.0046 and p<0.0015, respectively). was the best predictor of HSIL (area under the curve, AUC 0.819) while of SCC (AUC 0.856). In self-collected samples, best predicted HSIL (AUC 0.595) while SCC (AUC 0.812). Combined methylation yielded sensitivity and specificity for HSIL+ of 90.5% (95% CI 69.6% to 98.8%) and 70% (95% CI 45.7% to 88.1%), respectively, in clinician-collected samples, and 81.8% (95% CI 59.7% to 94.8%) and 47.6% (95% CI 25.7% to 70.2%), respectively, in self-collected samples. plus HPV16/HPV18 improved sensitivity for HSIL+ (95.2%, 95% CI 76.2% to 99.9%) but decreased specificity (55.0%, 95% CI 31.5% to 76.9%).
CONCLUSION
methylation is a potential triage strategy for the detection of HSIL/SCC in low-income and middle-income country.
Topics: Humans; Female; MicroRNAs; Uterine Cervical Neoplasms; Papua New Guinea; Early Detection of Cancer; Cell Adhesion Molecule-1; Adult; Triage; DNA Methylation; Middle Aged; Myelin and Lymphocyte-Associated Proteolipid Proteins; Papillomavirus Infections; Biomarkers, Tumor; Carcinoma, Squamous Cell; Specimen Handling; Young Adult; Sensitivity and Specificity; Vaginal Smears
PubMed: 38904134
DOI: 10.1136/bmjopen-2023-081282 -
Stem Cell Research Mar 2024Human brain organoids can serve as models to study myelination, a process orchestrated by oligodendrocytes. Real-time imaging provides new insights on the communication...
Human brain organoids can serve as models to study myelination, a process orchestrated by oligodendrocytes. Real-time imaging provides new insights on the communication of oligodendrocytes with neurons as well as demyelination processes in patient derived organoids. PLP1, a prominent myelin protein within the central nervous system, is associated with demyelinating diseases, such as Pelizaeus-Merzbacher. In this study, we generated a stable PLP1-Citrine reporter line (fPLP1) in human induced pluripotent stem cells (iPSCs) by CRISPR/Cas9 editing. fPLP1 facilitates visualization of PLP1 expression in living brain organoids, allowing time-lapse imaging of pre-myelinating and myelinating oligodendrocytes.
Topics: Humans; Myelin Proteolipid Protein; Induced Pluripotent Stem Cells; Pelizaeus-Merzbacher Disease; Myelin Sheath; Oligodendroglia
PubMed: 38219302
DOI: 10.1016/j.scr.2023.103295 -
Translational Psychiatry Jan 2024Tuberous sclerosis complex (TSC) is a genetic disease that causes benign tumors and dysfunctions in many organs, including the brain. Aside from the brain malformations,...
Tuberous sclerosis complex (TSC) is a genetic disease that causes benign tumors and dysfunctions in many organs, including the brain. Aside from the brain malformations, many individuals with TSC exhibit neuropsychiatric symptoms. Among these symptoms, autism spectrum disorder (ASD) is one of the most common co-morbidities, affecting up to 60% of the population. Past neuroimaging studies strongly suggested that the impairments in brain connectivity contribute to ASD, whether or not TSC-related. Specifically, the tract-based diffusion tensor imaging (DTI) analysis provides information on the fiber integrity and has been used to study the neuropathological changes in the white matter of TSC patients with ASD symptoms. In our previous study, curcumin, a diet-derived mTOR inhibitor has been shown to effectively mitigate learning and memory deficits and anxiety-like behavior in Tsc2 mice via inhibiting astroglial proliferation. Recently, gut microbiota, which is greatly influenced by the diet, has been considered to play an important role in regulating several components of the central nervous system, including glial functions. In this study, we showed that the abnormal social behavior in the Tsc2 mice can be ameliorated by the dietary curcumin treatment. Second, using tract-based DTI analysis, we found that the Tsc2 mice exhibited altered fractional anisotropy, axial and radial diffusivities of axonal bundles connecting the prefrontal cortex, nucleus accumbens, hypothalamus, and amygdala, indicating a decreased brain network. Third, the dietary curcumin treatment improved the DTI metrics, in accordance with changes in the gut microbiota composition. At the bacterial phylum level, we showed that the abundances of Actinobacteria, Verrucomicrobia, and Tenericutes were significantly correlated with the DTI metrics FA, AD, and RD, respectively. Finally, we revealed that the expression of myelin-associated proteins, myelin bassic protein (MBP) and proteolipid protein (PLP) was increased after the treatment. Overall, we showed a strong correlation between structural connectivity alterations and social behavioral deficits, as well as the diet-dependent changes in gut microbiota composition.
Topics: Humans; Mice; Animals; Diffusion Tensor Imaging; Autism Spectrum Disorder; Tuberous Sclerosis; Gastrointestinal Microbiome; Curcumin; Brain
PubMed: 38296969
DOI: 10.1038/s41398-024-02752-y