Biology subjects

Motiani, R. K.

Publications and source records attributed to Motiani, R. K..

3 recordsLinked to original sources

bioRxiv2023

Telomeres control regulation of the human Telomerase (hTERT) gene through non-telomeric TRF2 and independent of Telomere looping

The function of the human telomerase reverse transcriptase (hTERT) in the synthesis and maintenance of chromosome ends, or telomeres, is widely understood. Whether and how telomeres, on the other hand, influence hTERT regulation is relatively less studied. We found hTERT was transcriptionally altered depending on telomere length (TL). This resulted from TL-dependent binding of TRF2 between telomeres and the hTERT promoter. hTERT promoter-bound TRF2 was non-telomeric and did not involve the looping of telomeres to the hTERT promoter. Cell lines from different tissue types (fibrosarcoma (HT1080), colon cancer (HCT116), and breast cancer (MDA-MB-231), engineered for either telomere elongation/shortening gave increase/decrease in hTERT, respectively. Mechanistically, we show hTERT promoter-bound non-telomeric TRF2 recruits the canonical PRC2-complex inducing repressor histone H3K27-trimethylation in a TL-dependent fashion. This was further supported by TL-dependent promoter activity from an exogenously inserted hTERT reporter. Increase in TL over days followed by gradual decline, resulted in activation followed by repression of hTERT in a concerted manner, further implicating TL as a key factor for hTERT regulation. Notably on reprogramming primary fibroblasts to induced pluripotent stem cells (iPSCs), TRF2 loss from the hTERT promoter was evident along with telomere elongation and hTERT upregulation. Conversely, on telomere shortening in iPSCs, hTERT promoter-bound TRF2 was restored with marked reduction in hTERT further supporting the causal role of TL in hTERT transcription. Mechanisms of tight control of hTERT by TL shown here are likely to have major implications in telomere-related physiologies, particularly, cancer, ageing and pluripotency. TeaserTelomere length controls hTERT expression by modulating TRF2 distribution and PRC2-mediated repression, highlighting a self-regulatory mechanism in cancer.

cancer biology↗

bioRxiv2023

Mitochondrial calcium signaling mediated transcriptional regulation of keratin filaments is a critical determinant of melanogenesis

Mitochondria are versatile organelles that regulate several physiological functions. Many mitochondria-controlled processes are driven by mitochondrial Ca2+ signaling. However, role of mitochondrial Ca2+ signaling in melanosome biology remains unknown. Here, we show that pigmentation requires mitochondrial Ca2+ uptake. In vitro gain and loss of function studies demonstrated that Mitochondrial Ca2+ Uniporter (MCU) is crucial for melanogenesis while the MCU rheostats, MCUb and MICU1 negatively control melanogenesis. Zebrafish and mouse models showed that MCU plays a vital role in pigmentation in vivo. Mechanistically, MCU controls activation of transcription factor NFAT2 to induce expression of three keratins (keratin 5, 7 and 8), which we report as positive regulators of melanogenesis. Interestingly, keratin 5 in turn modulates mitochondrial Ca2+ uptake thereby this signaling module acts as a negative feedback loop that fine-tunes both mitochondrial Ca2+ signaling and melanogenesis. Mitoxantrone, an FDA approved drug that inhibits MCU, decreases physiological melanogenesis. Collectively, our data demonstrates a critical role for mitochondrial Ca2+ signaling in vertebrate pigmentation and reveal the therapeutic potential of targeting MCU for clinical management of pigmentary disorders. Given the centrality of mitochondrial Ca2+ signaling and keratin filaments in cellular physiology, this feedback loop may be functional in a variety of other pathophysiological conditions. HighlightsO_LIMCU complex mediated mitochondrial Ca2+ uptake is a novel regulator of vertebrate pigmentation C_LIO_LIKeratin filaments bridge mitochondrial Ca2+ signaling to melanosome biogenesis and maturation C_LIO_LITranscription factor NFAT2 connects mitochondrial Ca2+ dynamics to keratins expression C_LIO_LIMCU-NFAT2-Keratin 5 signaling module generates a negative feedback loop to maintain mitochondrial Ca2+ homeostasis and to ensure optimal melanogenesis C_LIO_LIInhibiting MCU with mitoxantrone, an FDA approved drug, leads to reduction in physiological pigmentation C_LI

cell biology↗

bioRxiv2023

Methotrimeprazine exerts antiviral and neuroprotective effects in Japanese encephalitis virus infection through activation of adaptive ER stress and autophagy

Japanese encephalitis virus (JEV) is the leading global cause of virus-induced encephalitis. Its pathogenesis is driven by a combination of neuronal cell death and neuroinflammation. We hypothesized that pharmacological upregulation of autophagy could exert a neuroprotective antiviral effect, and tested a panel of forty-two FDA-approved drugs that were shown to induce autophagy. Four drugs were tested in the JE mouse model based on in vitro protective effects on neuronal cell death, inhibition of viral replication, and anti-inflammatory effects in microglial cells. The antipsychotic phenothiazines Methotrimeprazine (MTP) and Trifluoperazine (TFP) showed a significant survival benefit with reduced virus titers in the brain, prevention of blood-brain barrier (BBB) breach, and inhibition of neuroinflammation. Both drugs were potent mTOR-independent autophagy flux inducers. Mechanistically MTP inhibited SERCA channel functioning, thereby resulting in rise in cytosolic calcium levels, and induction of a unique adaptive ER stress response. In virus infected drug treated cells, there was a strong transcriptional downregulation of type I interferon and interferon-stimulated genes and upregulation of cholesterol metabolic pathway genes. The drugs exerted an autophagy-dependent antiviral effect at the level of JEV protein translation/replication complex formation in diverse cell types. Inhibition of inflammatory cytokine/chemokine release from mouse microglial cells was partly autophagy-dependent. Our study suggests that MTP exerts a combined antiviral and anti-inflammatory effect in JEV infection, and has therapeutic potential to be repurposed for JE treatment.

microbiology↗