Prostaglandin E2receptor subtype EP2- and EP4-regulated gene expression profiling in human ciliary smooth muscle cells

Expression of the primate-specific LINC00473 RNA in mouse neurons promotes excitability and CREB-regulated transcription

The LINC00473 (Lnc473) gene has previously been shown to be associated with cancer and psychiatric disorders. Its expression is elevated in several types of tumors and decreased in the brains of patients diagnosed with schizophrenia or major depression. In neurons, Lnc473 transcription is strongly responsive to synaptic activity, suggesting a role in adaptive, plasticity-related mechanisms. However, the function of Lnc473 is largely unknown. Here, using a recombinant adeno-associated viral vector, we introduced a primate-specific human Lnc473 RNA into mouse primary neurons. We show that this resulted in a transcriptomic shift comprising downregulation of epilepsy-associated genes and a rise in cAMP response element binding protein (CREB) activity, which was driven by augmented CREB-regulated transcription coactivator 1 (CRTC1) nuclear localization. Moreover, we demonstrate that ectopic Lnc473 expression increased neuronal excitability as well as network excitability. These findings suggest that primates may possess a lineage-specific activity-dependent modulator of CREB-regulated neuronal excitability.

DNAJB1-PRKACA in HEK293T cells induces LINC00473 overexpression that depends on PKA signaling

Fibrolamellar carcinoma (FLC) is a primary liver cancer that most commonly arises in adolescents and young adults in a background of normal liver tissue and has a poor prognosis due to lack of effective chemotherapeutic agents. The DNAJB1-PRKACA gene fusion (DP) has been reported in the majority of FLC tumors; however, its oncogenic mechanisms remain unclear. Given the paucity of cellular models, in particular FLC tumor cell lines, we hypothesized that engineering the DP fusion gene in HEK293T cells would provide insight into the cellular effects of the fusion gene. We used CRISPR/Cas9 to engineer HEK293T clones expressing DP fusion gene (HEK-DP) and performed transcriptomic, proteomic, and mitochondrial studies to characterize this cellular model. Proteomic analysis of DP interacting partners identified mitochondrial proteins as well as proteins in other subcellular compartments. HEK-DP cells demonstrated significantly elevated mitochondrial fission, which suggests a role for DP in altering mitochondrial dynamics. Transcriptomic analysis of HEK-DP cells revealed a significant increase in LINC00473 expression, similar to what has been observed in primary FLC samples. LINC00473 overexpression was reversible with siRNA targeting of PRKACA as well as pharmacologic targeting of PKA and Hsp40 in HEK-DP cells. Therefore, our model suggests that LINC00473 is a candidate marker for DP activity.

LINC00473: A novel oncogenic long noncoding RNA in human cancers

Long noncoding RNAs (lncRNAs) have been found to play essential roles in the occurrence and development of multiple human cancers. Accumulating evidence has shown that LINC00473, an oncogenic lncRNA, is upregulated in various human malignancies and related to poor clinical outcomes. Besides, LINC00473 overexpression can promote cell proliferation, migration, and invasion through multiple potential mechanisms, indicating that it may serve as a novel prognostic biomarker and therapeutic target for human cancers. Here, we reviewed the biological functions, molecular mechanisms, and clinical implications of LINC00473 in human cancers.

Prostaglandins in the eye: Function, expression, and roles in glaucoma

Prostaglandins are small pro-inflammatory molecules derived from arachidonic acid that play roles in a multitude of biological processes including, but not limited to, inflammation, pain modulation, allergies, and bone formation. Prostaglandin analogues are the front-line medications for the treatment of glaucoma, a condition resulting in blindness due to the death of retinal ganglion cells. These drugs act by lowering intraocular pressure (IOP), a major risk factor for glaucoma. The currently used prostaglandin analogues (latanoprost, bimatoprost, tafluprost, and travoprost) mimic PGF2 and target one of the prostaglandin receptors (FP), though research into harnessing the other receptors using compounds like Sulprostone (EP3 receptor), or Iloprost (IP receptor) are currently ongoing. In this review, we summarize the research into each of the prostaglandin molecules (PGD2, PGE2, PGF2, PGI2, TXA2) and their respective receptors (DP, EP1, 2, 3, 4, FP, IP). We examine the modes of action of each of these receptors, their expression, their role in aqueous humour production and outflow within the eye, as well as their roles as medications for the treatment of glaucoma.

C6orf176: a novel possible regulator of cAMP-mediated gene expression

cAMP mediates diverse cellular signals including prostaglandin (PG) E(2)-mediated intraocular pressure (IOP)-lowering activity in human ocular ciliary smooth muscle cells (hCSM). We have identified gene regulatory networks and key genes upon activation of the cAMP pathway in hCSM, using novel agonists highly selective for PGE(2) receptor subtypes EP2 or EP4, which are G protein-coupled receptors well known to activate cAMP signaling. Here we describe a novel, EP2/EP4-induced, primate-specific gene of hitherto unknown function, also known as C6orf176 (chromosome 6 open reading frame 176) and recently reclassified as noncoding RNA in NCBI's database. Its expression, as determined by quantitative real-time RT-PCR (qRT-PCR), is dramatically upregulated (>2,000-fold) subsequent to transduction of EP2/EP4/Gs/cAMP signaling not only in hCSM, but also in HEK cells overexpressing the recombinant receptors. Moreover, activation of other IOP lowering, Gs-coupled prostanoid receptors, such as DP1 and IP, as well as a direct activator of adenylyl cyclase, forskolin, also substantially upregulated C6orf176 in hCSM, while FP and TP, which are Gq-coupled prostanoid receptor subtypes, did not. Novel transcript variants carrying open reading frames, derived from an at least 67 kb genomic locus on chromosome 6q27 with putative alternative transcription start sites, were identified. Transcriptional upregulation of transcript variants as well as of two genes expressed in antisense orientation that partially overlap the transcribed C6orf176 region was observed, to varying degrees, subsequent to induction of cAMP signaling using various agonists. Small interfering RNA-mediated C6orf176 gene silencing experiments showed modulation of several cAMP-responsive genes. These transcriptional activities identify C6orf176 as a potential biomarker and/or therapeutic target in context with diseases linked to deregulated cAMP signaling. Also, the cAMP-inducible C6orf176 gene locus could be useful as a model system for studying transcriptional regulation by chromatin and RNA polymerase II.