Reddy, A. B. M. | Search bioRxiv

bioRxiv2024

TGF-beta/OPTN/FOXC1/miR-200 axis regulates intraocular pressure dynamics in trabecular meshwork cells

Glaucoma is the second leading cause of irreversible blindness globally, with elevated intraocular pressure (IOP) being its primary risk factor. Current therapeutic approaches, such as beta-blockers, alpha-adrenergic agonists, Rho-kinase inhibitors, etc., aim to reduce IOP levels. However, the molecular mechanisms underlying altered IOP remain poorly understood. In this study, we have treated primary human trabecular meshwork cells (HTM) with exogenous dexamethasone (dex) or transforming growth factor beta-2 (TGF-{beta}2) to investigate its effects on glaucoma candidate genes. Interestingly, our findings reveal that FOXC1 acts as a repressor to CYP1B1, and optineurin (OPTN) facilitates the ubiquitination of FOXC1, thereby inducing CYP1B1 expression. Further, we discovered that the miR-200 family and other miRNAs regulate these glaucoma-candidate genes. Furthermore, TGF-{beta}2 downregulates the miR-200 family, whereas the miR-200 family targets FOXC1, exerting reversible effects by altering the extracellular matrix. FOXC1 positively regulates CLOCK, one of its target genes. Besides, CLOCK/BMAL1 has binding sites on miR-200 family promoters. Modulating the TGF-{beta}2/OPTN/FOXC1/miR-200 axis appears critical in regulating IOP dynamics through CLOCK/BMAL1-mediated daily rhythmicity in the anterior segment of the eye. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=133 SRC="FIGDIR/small/593675v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@1c1fb5eorg.highwire.dtl.DTLVardef@5de067org.highwire.dtl.DTLVardef@1378e7borg.highwire.dtl.DTLVardef@6b53d1_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2020

Target of Rapamycin: function in abiotic stress tolerance in Arabidopsis and its involvement in a possible cross-talk with ribosomal proteins

The Target of Rapamycin (TOR) protein kinase reprograms cellular metabolism under various environmental stresses. The overexpression of TOR in Arabidopsis resulted in increased plant growth including yield and biomass when compared with the wild type under both controlled and limited water conditions. In the present investigation, we report that Arabidopsis plants overexpressing TOR exhibited enhanced tolerance to the osmotic and salt stress treatments. Further to determine the role of TOR in abiotic stresses other than water limiting conditions, which were observed earlier in rice, we have treated high and medium TOR expressing Arabidopsis plants, ATR-1.4.27 and ATR-3.7.32 respectively, with stress-inducing chemical agents such as Mannitol (100 mM), NaCl (150 mM), Sorbitol (200 mM) and PEG (7%). Both the lines, ATR-1.4.27 and ATR-3.7.32 exhibited enhanced tolerance to these stresses. These lines also had increased proline and total chlorophyll contents under stress conditions compared with their corresponding WT counterparts. The upregulation of several osmotic stress inducible genes in Arabidopsis transgenic lines indicated the role of TOR in modulating multi-stress tolerance. In the present investigation, we have also analyzed the transcriptional upregulation of ribosomal protein large and small subunit (RPL and RPS) genes in AtTOR overexpressing rice transgenic lines, TR-2.24 and TR-15.1 generated earlier (Bakshi et al., 2017a), which indicated that TOR also positively regulates the transcription of ribosomal proteins (RP) along with the synthesis of rRNAs. Also, the observations from phosphoproteomic analysis in SALK lines of various Arabidopsis T-DNA insertion mutants of ribosomal proteins showed differential regulation in phosphorylation of p70kDa ribosomal protein S6K1 and comparative analysis of phosphorylation sites for RSK (Ribosomal S6 Kinases) in RPL6, RPL18, RPL23, RPL24 and RPS28C proteins of Arabidopsis, Interestingly, rice showed similarity in their peptide sequences and Ser/Thr positions. These results suggest that the phosphorylation of S6K1 is controlled by loss/ inhibition of ribosomal protein function to switch on/ off the translational regulation for balanced growth and the pathways of both RPs and TOR are interlinked in a cyclic manner via phosphorylation of S6K1 as a modulatory step.

plant biology↗