Biology subjects

Mohapatra, P.

Publications and source records attributed to Mohapatra, P..

4 recordsLinked to original sources

bioRxiv2021

MINK1 modulates 5FU resistance in OSCC through AKT/MDM2 mediated regulation of p53

Cisplatin, 5FU and docetaxel (TPF) are the most common chemotherapy regimen used for advanced OSCC. However, many cancer patients experience relapse, continued tumor growth, and spread due to drug resistance, which leads to treatment failure and metastatic disease. Here, using a CRISPR/Cas9 based kinome knockout screening, Misshapen-like kinase 1 (MINK1) is identified as an important mediator of 5FU resistance in OSCC. Analysis of clinical samples demonstrated significantly higher MINK1 expression in the tumor tissues of chemotherapy non-responder as compared to chemotherapy responders. The nude mice and zebrafish xenograft experiments indicate that knocking out MINK1 restores 5FU mediated cell death in chemoresistant OSCC. An antibody based phosphorylation array screen revealed MINK1 as a negative regulator of p53. Mechanistically, MINK1 modulates AKT phosphorylation at Ser473, which enables p-MDM2 (Ser 166) mediated degradation of p53. We also identified lestaurtinib as a potent inhibitor of MINK1 kinase activity. The patient derived TPF resistant cell based xenograft data suggest that lestaurtinib restores 5FU sensitivity and facilitates a significant reduction of tumor burden. Overall, our study suggests that MINK1 is a major driver of 5FU resistance in OSCC. The novel combination of MINK1 inhibitor lestaurtinib and 5FU needs further clinical investigation in advanced OSCC.

cancer biology↗

bioRxiv2021

Evaluation of a high-throughput deorphanization strategy to identify cytochrome p450s important for odor degradation in Drosophila

Members of the cytochrome p450 (CYP) enzyme family are abundantly expressed in insect olfactory tissues, where they are thought to act as Odorant Degrading Enzymes (ODEs). However, their contribution to olfactory signaling in vivo is poorly understood. This is due in part to the challenge of identifying which of the dozens of antennal-expressed CYPs might inactivate a given odorant. Here, we tested a high-throughput deorphanization strategy in Drosophila to identify CYPs that are transcriptionally induced by exposure to a plant volatile. We discovered three CYPs selectively upregulated by the odorant using transcriptional profiling. Although these CYPs are shown to be broadly expressed in the antenna in non-neuronal cells, electrophysiological recordings from CYP mutants did not reveal any changes in olfactory neuron responses to the odorant. Neurons were desensitized by pre-exposing flies to the odorant, but this effect was similar in CYP mutants. Together, our data suggest that this transcriptomic approach may not be useful for identifying CYPs that contribute to olfactory signaling. We go on to show that some CYPs have highly restricted expression patterns in the antenna, and suggest that such CYPs may be useful candidates for further studies on olfactory CYP function.

neuroscience↗

bioRxiv2021

Functional characterization of odor responses and gene expression changes in olfactory co-receptor mutants in Drosophila

Two large families of olfactory receptors, the Odorant Receptors (ORs) and the Ionotropic Receptors (IRs), mediate responses to most odors in the insect olfactory system. Individual odor binding "tuning" OR receptors are expressed by olfactory neurons in basiconic and trichoid sensilla and require the co-receptor Orco to function. The situation for IRs is more complex. Different tuning IR receptors are expressed by olfactory neurons in coeloconic sensilla and rely on either the Ir25a or Ir8a co-receptors; some evidence suggests that Ir76b may also act as a coreceptor, but its function has not been systematically examined. This is particularly important as recent data indicate that nearly all coeloconic olfactory neurons co-express Ir25a, Ir8a, and Ir76b. Here, we report the effects of Drosophila olfactory co-receptor mutants on odor detection by coeloconic olfactory neurons and determine their broader impact on gene expression through RNASeq analysis. We demonstrate that Ir76b and Ir25a function together in all amine-sensing olfactory receptor neurons. In most neurons, loss of either co-receptor abolishes amine responses, whereas in ac1 sensilla, amine responses persist in the absence of Ir76b or Ir25a, but are lost in a double-mutant. Such responses do not require Ir8a. Conversely, acid-sensing ORNs require Ir8a, but not Ir76b or Ir25a. Using antennal transcriptional profiling, we find that the expression of acid-sensing IR receptors is significantly reduced in Ir8a mutants, but is unaffected by the loss of Ir25a or Ir76b. Similarly, select OR tuning receptors are also downregulated in Orco2 mutants. In contrast, expression of amine-sensing IR receptors is mostly unchanged in Ir25a and Ir76b mutants. Together, our data reveal new aspects of co-receptor function in the olfactory system. SummaryInsect vectors of human disease rely on their sense of smell to locate humans for blood meals. A critical first step in olfaction is the odorant-induced activation of receptors on olfactory neurons. There are two major olfactory receptor families in insects, with each species having dozens of different odorant-binding "tuning" receptors. The receptor complexes also contain non-tuning co-receptors, which are highly conserved across insect species and are required for function. Here we characterize co-receptor mutants with electrophysiological recordings and transcriptome analysis in Drosophila. Our findings resolve the differential co-receptor dependence of olfactory neuron responses to volatile amines and acids. We also report changes in antennal gene expression that result from the absence of these co-receptors. Most notably, the absence of some co-receptors leads to a selective loss of transcript expression for the tuning olfactory receptors whose function depends on the missing co-receptors. Together our data provide new insight into the roles of co-receptors in insect olfaction.

neuroscience↗

bioRxiv2020

CMTM6 drives cisplatin resistance in OSCC by regulating AKT mediated Wnt signaling

Chemoresistance is one of the important factors for treatment failure in OSCC, which can culminate in progressive tumor growth and metastatic spread. Rewiring tumor cells to undergo drug-induced apoptosis is a promising way to overcome chemoresistance, which can be achieved by identifying the causative factors for acquired chemoresistance. In this study, to explore the key cisplatin resistance triggering factors, we performed global proteomic profiling of OSCC lines representing with sensitive, early and late cisplatin-resistant patterns. The top ranked up-regulated protein appeared to be CMTM6. We found CMTM6 to be elevated in both early and late cisplatin-resistant cells with respect to the sensitive counterpart. Analyses of OSCC patient samples indicate that CMTM6 expression is upregulated in chemotherapy-non-responder tumors as compared to chemotherapy-naive tumors. Stable knockdown of CMTM6 restores cisplatin-mediated cell death in chemoresistant OSCC lines. Similarly, upon CMTM6 overexpression in CMTM6KD lines, the cisplatin resistant phenotype was efficiently rescued. Mechanistically, it was found that CMTM6 interacts with membrane bound Enolase-1 and stabilized its expression, which in turn activates the AKT-GSK3{beta} mediated Wnt signaling. CMTM6 triggers the translocation of {beta}-catenin into the nucleus, which elevates the Wnt target pro-survival genes like Cyclin D, c-Myc and CD44. Moreover, incubation with lithium chloride, a Wnt signaling activator, efficiently rescued the chemoresistant phenotype in CMTM6KD OSCC lines. In a patient-derived cell xenograft model of chemoresistant OSCC, knock-down of CMTM6 restores cisplatin induced cell death and results in significant reduction of tumor burden. CMTM6 has recently been identified as a stabilizer of PD-L1 and henceforth it facilitates immune evasion by tumor cells. Herewith for the first time, we uncovered another novel role of CMTM6 as one of the major driver of cisplatin resistance.

cancer biology↗