Biology subjects

Maitra, S.

Publications and source records attributed to Maitra, S..

8 recordsLinked to original sources

bioRxiv2024

HIF2α negatively regulates MYCN protein levels and promotes a low-risk noradrenergic phenotype in neuroblastoma.

The role of HIF2, encoded by EPAS1, in neuroblastoma remains controversial. Here we demonstrate that induction of high levels of HIF2 in MYCN-amplified neuroblastoma cells results in a rapid and profound reduction of the oncoprotein MYCN. This is followed by an upregulation of genes characteristic of noradrenergic cells in the adrenal medulla. Additionally, upon induction of HIF2, the proliferation rate drops substantially, and cells develop elongated neurite-like protrusions, indicative of differentiation. In vivo HIF2 induction in established xenografts significantly attenuates tumour growth. Notably, analysis of sequenced neuroblastoma patient samples, revealed a negative correlation between EPAS1 and MYCN expression and a strong positive correlation between EPAS1 expression, high expression levels of noradrenergic markers, and improved patient outcome. This was paralleled by analysis of human adrenal medulla datasets wherein EPAS1 expression was prominent in populations with high expression levels of genes characteristic of noradrenergic chromaffin cells. Our findings show that high levels of HIF2 in neuroblastoma, leads to drastically reduced MYCN protein levels, cell cycle exit, and noradrenergic cell differentiation. Taken together, our results challenge the dogma that HIF2 acts as an oncogene in neuroblastoma and rather suggest that HIF2 has potential tumour suppressor capacity in this particular disease. Significance statementHIF2 has been proposed as a neuroblastoma oncogene and a tractable target for clinical intervention, this has been questioned by several studies. Thus, it is necessary to move beyond correlative studies and better determine the function of HIF2 in neuroblastoma. Our study shows that induced expression of HIF2 in MYCN-amplified neuroblastoma substantially reduces MYCN protein levels and attenuates proliferation while it induces several features of noradrenergic differentiation and impedes xenograft tumour growth. Together with bioinformatic analysis of sequenced neuroblastoma patient samples and the developing human adrenal medulla, this couples HIF2 to low-risk neuroblastoma with a substantially better patient outcome. Thus, in neuroblastoma HIF2 exhibit tumour suppressor capacity rather than oncogenic capacity.

cancer biology↗

bioRxiv2024

New tools to monitor Pseudomonas aeruginosa infection and biofilms in vivo in C. elegans.

Antimicrobial resistance is a growing health problem. Pseudomonas aeruginosa is a pathogen of major concern because of its multidrug resistance and global threat, especially in health-care settings. The pathogenesis and drug resistance of P. aeruginosa depends on its ability to form biofilms, making infections chronic and untreatable as the biofilm protects against antibiotics and host immunity. A major barrier to developing new antimicrobials is the lack of in vivo biofilm models. Standard microbiological testing is usually performed in vitro using planktonic bacteria, without representation of biofilms, reducing translatability. Here we develop tools to study both infection and biofilm formation by P. aeruginosa in vivo to accelerate development of strategies targeting infection and pathogenic biofilms. Using the nematode Caenorhabditis elegans and P. aeruginosa reporters combined with in vivo imaging we show that fluorescent P. aeruginosa reporters that form biofilms in vitro can be used to visualise tissue infection. Using automated tracking of C. elegans movement, we find that that the timing of this infection corresponds with a decline in health endpoints. In a mutant strain of P. aeruginosa lacking RhlR, a transcription factor that controls quorum sensing and biofilm formation, we find reduced capacity of P. aeruginosa to form biofilms, invade host tissues and negatively impact healthspan and survival. Our findings suggest that RhlR could be a new antimicrobial target to reduce P. aeruginosa biofilms and virulence in vivo and C. elegans could be used to more effectively screen for new drugs to combat antimicrobial resistance.

microbiology↗

bioRxiv2024

FDA approved PDE4 inhibitors reduce the dominant toxicity of ALS/FTD associated CHCHD10S59L

Mutations in coiled-coil-helix-coiled-coil-helix domain containing 10(CHCHD10) have been identified as a genetic cause of amyotrophic lateral sclerosis and/or frontotemporal dementia(ALS-FTD). In our previous studies using in vivo Drosophila model expressing C2C10HS81L, and human cell models expressing CHCHD10S59L, we have identified that the PINK1/Parkin pathway is activated and causes cellular toxicity. Furthermore, we demonstrated that pseudo-substrate inhibitors for PINK1 and mitofusin2 agonists mitigated the cellular toxicity of CHCHD10S59L. Evidences using in vitro/ in vivo genetic and chemical tools indicate that inhibiting PINK1 would be the most promising treatment for CHCHD10S59L-induced diseases. Therefore, we have investigated cellular pathways that can modulate the PINK1/Parkin pathway and reduce CHCHD10S59L-induced cytotoxicity. Here, we report that FDA-approved PDE4 inhibitors reduced CHCHD10S59L-induced morphological and functional mitochondrial defects in human cells and an in vivo Drosophila model expressing C2C10HS81L. Multiple PDE4 inhibitors decreased PINK1 accumulation and downstream mitophagy induced by CHCHD10S59L. These findings suggest that PDE4 inhibitors currently available in the market may be repositioned to treat CHCHD10S59L-induced ALS-FTD and possibly other related diseases.

neuroscience↗

bioRxiv2024

Differences in Methanotrophic Community Structure in Two Methane-Rich Habitats: Oil Natural Gas Field & Paddy Field

Methanotrophic bacterial isolates were identified in this study using the molecular detection method, isolated using microbiological techniques, and studied their cellular shape using atomic force microscopy. Two methanotrophic bacterial species belonging to the Methylocaldum and Methylomonas genera were provisionally designated as Isolate 1 and Isolate 5, thus isolated from the Oil-Natural Gas Field and Paddy Field, respectively. The Oil-Natural Gas Field Isolate 1 showed 91.82-97.25% sequence homology to the reference Methanotrophic species, whereas Paddy Field Isolate 5 showed 79.72-84.99% sequence homology to the reference Methylomonas species in the NCBI database. As per the phylogenetic analysis, Oil-Natural Gas Field Isolate 1 and Paddy Field Isolate 5 are possibly new species of Methylocaldum and Methylomonas genus, respectively. In addition, the microscopic study also supported the molecular identification and phylogenetic analysis of isolated species by showing the cocci and rod shapes for the Oil-Natural Gas Field Isolate 1 and Paddy Field Isolate 5, respectively.

microbiology↗

bioRxiv2023

In-vivo Therapeutic Evaluation of the Wound Healing Potential of Ethanolic Extract of Trichilia heudelotii Leaves in Wistar Rats

BackgroundTrichilia heudelotii belongs to the Meliaceae family and is commonly used in indigenous African medicine to prevent and treat various microbial ailments. MethodsTrichilia heudelotiis ethanolic leaf extracts contains phytochemicals which was studied to demonstrate its wound-healing properties. Phytochemical screening of leaf extracts contains flavonoids, phenolics, tannins, terpenoids, saponins, and alkaloids, which play a vital part in the healing process. Overall, quantitative, and qualitative screening were performed to evaluate the therapeutic efficacy of Trichilia heudelotiis phytochemicals for wound treatment. ResultsThe wound-healing potency was evaluated using different concentrations of formulated oil extracts (0.5, 1.0, and 2.0g/10g) on fresh wounds inflicted on Wistar rats using the excision model. Healing capacity was assessed based on rate of wound contracting ability, time of wound closure, and epithelisation period. The results shows that leaf extract oils exhibited significant wound healing capacity (p<0.05) compared with controls. On the 18th day in the infected group using 2.0/10g extract formulated ointment, 100% wound closure was observed. On day 21, using 0.5/10g and 1.0/ 10g, extract formulated ointment compared with controls which exhibited 79% and 89%, respectively. In addition, histopathological characteristics show increased and well-organized new bands of collagen and fibroblasts in the extract formulated treatment than in the controls, which supports the wounding healing potential of the plant. This is the first report providing therapeutic evidence for the wound healing activity of ethanolic leaf extract on Wistar rats. ConclusionThis indicate the evidence that establish the traditional use of Trichilia heudelotii extract for treating skin infections and wounds. The results also raise the possibility of developing a commercialized medicinal product-based venture based on this extract. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=176 SRC="FIGDIR/small/571768v2_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@18dbe8corg.highwire.dtl.DTLVardef@d8eb90org.highwire.dtl.DTLVardef@15152f7org.highwire.dtl.DTLVardef@1de83e_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2023

The 21-base pair deletion mutant Calpain 3 does not inhibit wild-type Calpain 3 activity

IntroductionCalpain 3 is one of the calpain protease family members, which is a calcium-dependent proteolytic enzyme predominantly expressed in skeletal muscle. Loss-of-function mutations in the Calpain 3 gene have been related to autosomal recessive Limb-Girdle Muscular Dystrophy 1 (LGMDR1), a common form of muscular dystrophy. Recently, the heterozygous 21-bp deletion mutation of the Calpain 3 gene has been reported to cause autosomal dominant Limb-Girdle Muscular Dystrophy 4 (LGMDD4). According to its dominant inheritance pattern, it has been suggested that the deletion mutant proteins act in a dominant-negative manner. Therefore, we examined whether the mutant protein can suppress the activity of wild-type Calpain 3 and has any dominant toxicity in cell culture and in vivo Drosophila models. MethodsA human cell culture (HeLa cells) model with the transient transfection of human wild-type and mutant Calpain 3 and in vivo Drosophila models overexpressing wild-type and mutant Drosophila Calpain A and B were utilized in this study to assess dominant effects of Calpain 3 21-bp deletion mutant. Western blot analysis was used to determine protein stability and catalytic activity in cell culture. External eye morphology and muscle integrity were examined to observe dominant toxicity in Drosophila models. ResultsThe 21-bp deletion mutation of Calpain 3 resulted in catalytic inactivation, which did not inhibit wild-type Calpain 3 autolytic and catalytic activity against Calpastatin in HeLa cells. In addition, the mutant protein was normally processed by wild-type Calpain 3. Overexpression of wild-type and deletion mutant Calpain 3 in the Drosophila eye and muscles did not exhibit significant developmental and age-related dominant toxicity. DiscussionWe provide evidence that mutant Calpain 3 does not suppress wild-type Calpain 3 activity. Rather, it is a mutant lacking autocatalytic processing activity like many other loss-of-function Calpain 3 mutants causing LGMDR1. Our results implicate that the stability of the heteromeric mutant and wild-type Calpain 3 complexes may be affected without inhibiting the wild-type activity per se. However, a more thorough investigation is necessary to understand the molecular mechanism and dominant inheritance of the heterozygous 21-bp deletion mutation in LGMDD4.

cell biology↗

bioRxiv2022

ADAM10 pharmacological inhibition modifies the expression of components of the dopaminergic system

Dopamine is a primary neurotransmitter associated with memory formation, emotional control, reward processing and other higher order mental functions. Altered dopamine signaling is implied in several neuropsychiatric, neurodevelopmental and neurodegenerative disorders including Alzheimers disease. Age-related memory decline often presents itself with spectrum of overtly behavioral responses in patients diagnosed with Alzheimers disease, thus suggesting that an alteration of dopaminergic transmission could account for the psychotic symptoms observed along the pathology. Since less sAPP production due to reduced -secretase activity is a direct contributor of compromised neuroprotection and can impart higher vulnerability to cellular insults, we explored the impact of specific inhibition of ADAM10, the main neuronal -secretase, on dopamine system components in cultured human SH-SY5Y neuroblastoma cells. We found that dopamine receptor D4 protein levels were dose-dependently down regulated by GI254023X, but not by the ADAM17-specific inhibitor TAPI-0. We then established that GI254023X operates at a transcriptional levels. Furthermore, we showed that GI254023X treatment also significantly increased the levels of active PKA as well as the transcription of the dopamine-degrading enzymes catechol-O-methyltransferase, monoamine oxidase A and monoamine oxidase B. Altogether, our data propose that ADAM10 inhibition modulates the dopaminergic system to possibly trigger psychosis in Alzheimers disease.

neuroscience↗

bioRxiv2021

A conserved Guided Entry of Tail-anchored pathway is involved in the trafficking of tail-anchored membrane proteins in Plasmodium falciparum.

Tail-anchored (TA) proteins are defined by the absence of N-terminus signal sequence and the presence of a single transmembrane domain (TMD) proximal to their extreme C-terminus. They play fundamental roles in cellular processes including vesicular trafficking, protein translocation and quality control. Accordingly, TA proteins are post-translationally integrated by the Guided Entry of TA (GET) pathway to the cellular membranes; with their N-terminus oriented towards the cytosol and C-terminus facing the organellar lumen. The TA repertoire and the GET machinery have been extensively characterized in the yeast and mammalian systems, however, they remain elusive in the human malaria parasite Plasmodium falciparum. In this study, we bioinformatically predicted a total of 63 TA proteins in the P. falciparum proteome and revealed the association of their subset with the P. falciparum homolog of Get3 (PfGet3). In addition, our proximity labelling studies either definitively identified or shortlisted the other eligible GET constituents, and our in vitro association studies validated associations between PfGet3 and the corresponding homologs of Get4 and Get2 in P. falciparum. Collectively, this study reveals the presence of proteins with hallmark TA signatures and the involvement of evolutionary conserved GET trafficking pathway for their targeted delivery within the parasite. SynopsisTail-anchored (TA) proteins, characterized by an absence of N-terminal signal sequence and the presence of a transmembrane domain near the C-terminus, are post-translationally inserted at organellar membranes by the conserved multi-component Guided Entry of TA (GET) pathway. Here, we identified the putative homologs of GET machinery in the human malaria parasite Plasmodium falciparum and revealed their association with a subset of bioinformatically predicted 63 putative TA proteins, thereby validating the functional existence of this trafficking pathway within the apicomplexan parasite. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=191 HEIGHT=200 SRC="FIGDIR/small/442402v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@1c0239org.highwire.dtl.DTLVardef@d5ffbaorg.highwire.dtl.DTLVardef@1884a50org.highwire.dtl.DTLVardef@c6df7d_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗