Role of ectopic olfactory receptors in glucose and lipid metabolism

Non-canonical olfactory pathway activation induces cell fusion of cervical cancer cells

Multinucleation occurs in various types of advanced cancers and contributes to their malignant characteristics, including anticancer drug resistance. Therefore, inhibiting multinucleation can improve cancer prognosis; however, the molecular mechanisms underlying multinucleation remain elusive. Here, we introduced a genetic mutation in cervical cancer cells to induce cell fusion-mediated multinucleation. The olfactory receptor OR1N2 was heterozygously mutated in these fused cells; the same OR1N2 mutation was detected in multinucleated cells from clinical cervical cancer specimens. The mutation-induced structural change in the OR1N2 protein activated protein kinase A (PKA), which, in turn, mediated the non-canonical olfactory pathway. PKA phosphorylated and activated furin protease, resulting in the cleavage of the fusogenic protein syncytin-1. Because this cleaved form of syncytin-1, processed by furin, participates in cell fusion, furin inhibitors could suppress multinucleation and reduce surviving cell numbers after anticancer drug treatment. The improved anticancer drug efficacy indicates a promising therapeutic approach for advanced cervical cancers.

Ecnomotopic olfactory receptors in metabolic regulation

Olfactory receptors are seven-transmembrane G-protein-coupled receptors on the cell surface. Over the past few decades, evidence has been mounting that olfactory receptors are not unique to the nose and that their ectopic existence plays an integral role in extranasal diseases. Coupled with the discovery of many natural or synthetic odor-compound ligands, new roles of ecnomotopic olfactory receptors regulating blood glucose, obesity, blood pressure, and other metabolism-related diseases are emerging. Many well-known scientific journals have called for attention to extranasal functions of ecnomotopic olfactory receptors. Thus, the prospect of ecnomotopic olfactory receptors in drug target research has been greatly underestimated. Here, we have provided an overview for the role of ecnomotopic olfactory receptors in metabolic diseases, focusing on their effects on various metabolic tissues, and discussed the possible molecular biological and pathophysiological mechanisms, which provide the basis for drug development and clinical application targeting the function of ecnomotopic olfactory receptors via literature machine learning and screening.

Pan-cancer analysis identifies olfactory receptor family 7 subfamily A member 5 as a potential biomarker for glioma

Background

Human olfactory receptors (ORs) account for approximately 60% of all human G protein-coupled receptors. The functions of ORs extend beyond olfactory perception and have garnered significant attention in tumor biology. However, a comprehensive pan-cancer analysis of ORs in human cancers is lacking.

Methods

Using data from public databases, such as HPA, TCGA, GEO, GTEx, TIMER2, TISDB, UALCAN, GEPIA2, and GSCA, this study investigated the role of olfactory receptor family 7 subfamily A member 5 (OR7A5) in various cancers. Functional analysis of OR7A5 in LGG and GBM was performed using the CGGA database. Molecular and cellular experiments were performed to validate the expression and biological function of OR7A5 in gliomas.

Results

The results revealed heightened OR7A5 expression in certain tumors, correlating with the expression levels of immune checkpoints and immune infiltration. In patients with gliomas, the expression levels of OR7A5 were closely associated with adverse prognosis, 1p/19p co-deletion status, and wild-type IDH status. Finally, in vitro experiments confirmed the inhibitory effect of OR7A5 knockdown on the proliferative capacity of glioma cells and on the expression levels of proteins related to lipid metabolism.

Conclusion

This study establishes OR7A5 as a novel biomarker, potentially offering a novel therapeutic target for gliomas.

Olfactory receptors impact pathophysiological processes of lung diseases in bronchial epithelial cells

BACKGROUND

Therapeutic options for steroid-resistant non-type 2 inflammation in obstructive lung diseases are limited. Bronchial epithelial cells are key in the pathogenesis by releasing the central proinflammatory cytokine interleukine-8 (IL-8). Olfactory receptors (ORs) are expressed in various cell types. This study examined the drug target potential of ORs by investigating their impact on associated pathophysiological processes in lung epithelial cells.

METHODS

Experiments were performed in the A549 cell line and in primary human bronchial epithelial cells. OR expression was investigated using RT-PCR, Western blot, and immunocytochemical staining. OR-mediated effects were analyzed by measuring 1) intracellular calcium concentration via calcium imaging, 2) cAMP concentration by luminescence-based assays, 3) wound healing by scratch assays, 4) proliferation by MTS-based assays, 5) cellular vitality by Annexin V/PI-based FACS staining, and 6) the secretion of IL-8 in culture supernatants by ELISA.

RESULTS

By screening 100 potential OR agonists, we identified two, Brahmanol and Cinnamaldehyde, that increased intracellular calcium concentrations. The mRNA and proteins of the corresponding receptors OR2AT4 and OR2J3 were detected. Stimulation of OR2J3 with Cinnamaldehyde reduced 1) IL-8 in the absence and presence of bacterial and viral pathogen-associated molecular patterns (PAMPs), 2) proliferation, and 3) wound healing but increased cAMP. In contrast, stimulation of OR2AT4 by Brahmanol increased wound healing but did not affect cAMP and proliferation. Both ORs did not influence cell vitality.

CONCLUSION

ORs might be promising drug target candidates for lung diseases with non-type 2 inflammation. Their stimulation might reduce inflammation or prevent tissue remodeling by promoting wound healing.

Role of Ectopic Olfactory Receptors in the Regulation of the Cardiovascular-Kidney-Metabolic Axis

Olfactory receptors (ORs) represent one of the largest yet least investigated families of G protein-coupled receptors in mammals. While initially believed to be functionally restricted to the detection and integration of odors at the olfactory epithelium, accumulating evidence points to a critical role for ectopically expressed ORs in the regulation of cellular homeostasis in extranasal tissues. This review aims to summarize the current state of knowledge on the expression and physiological functions of ectopic ORs in the cardiovascular system, kidneys, and primary metabolic organs and emphasizes how altered ectopic OR signaling in those tissues may impact cardiovascular-kidney-metabolic health.

Trace Amine-Associated Receptors and Monoamine-Mediated Regulation of Insulin Secretion in Pancreatic Islets

Currently, metabolic syndrome treatment includes predominantly pharmacological symptom relief and complex lifestyle changes. Trace amines and their receptor systems modulate signaling pathways of dopamine, norepinephrine, and serotonin, which are involved in the pathogenesis of this disorder. Trace amine-associated receptor 1 (TAAR1) is expressed in endocrine organs, and it was revealed that TAAR1 may regulate insulin secretion in pancreatic islet β-cells. For instance, accumulating data demonstrate the positive effect of TAAR1 agonists on the dynamics of metabolic syndrome progression and MetS-associated disease development. The role of other TAARs (TAAR2, TAAR5, TAAR6, TAAR8, and TAAR9) in the islet's function is much less studied. In this review, we summarize the evidence of TAARs' contribution to the metabolic syndrome pathogenesis and regulation of insulin secretion in pancreatic islets. Additionally, by the analysis of public transcriptomic data, we demonstrate that TAAR1 and other TAAR receptors are expressed in the pancreatic islets. We also explore associations between the expression of TAARs mRNA and other genes in studied samples and demonstrate the deregulation of TAARs' functional associations in patients with metabolic diseases compared to healthy donors.

A Two-Step Transcriptome Analysis of the Human Heart Reveals Broad and Disease-Responsive Expression of Ectopic Olfactory Receptors

G-protein-coupled receptors (GPCRs) are critical regulators of cardiac physiology and a key therapeutic target for the treatment of heart disease. Ectopic olfactory receptors (ORs) are GPCRs expressed in extra-nasal tissues which have recently emerged as new mediators in the metabolic control of cardiac function. The goals of this study were to profile OR gene expression in the human heart, to identify ORs dysregulated by heart failure caused by ischemic cardiomyopathy, and to provide evidence suggestive of a role for those altered ORs in the pathogenesis of heart failure. Left ventricular tissue from heart failure patients (n = 18) and non-failing heart samples (n = 4) were subjected to a two-step transcriptome analysis consisting of the quantification of 372 distinct OR transcripts on real-time PCR arrays and simultaneous determination of global cardiac gene expression by RNA sequencing. This strategy led to the identification of >160 ORs expressed in the human heart, including 38 receptors differentially regulated with heart failure. Co-expression analyses predicted the involvement of dysregulated ORs in the alteration of mitochondrial function, extracellular matrix remodeling, and inflammation. We provide this dataset as a resource for investigating roles of ORs in the human heart, with the hope that it will assist in the identification of new therapeutic targets for the treatment of heart failure.

Emerging roles of olfactory receptors in glucose metabolism

Olfactory receptors (ORs) are widely expressed in extra-nasal tissues, where they participate in the regulation of divergent physiological processes. An increasing body of evidence over the past decade has revealed important regulatory roles for extra-nasal ORs in glucose metabolism. Recently, nonodorant endogenous ligands of ORs with metabolic significance have been identified, implying the therapeutic potential of ORs in the treatment of metabolic diseases, such as diabetes and obesity. In this review, we summarize current understanding of the expression patterns and functions of ORs in key tissues involved in glucose metabolism modulation, describe odorant and endogenous OR ligands, explain the biased signaling downstream of ORs, and outline OR therapeutic potential.

Not Only COVID-19: Involvement of Multiple Chemosensory Systems in Human Diseases

Chemosensory systems are deemed marginal in human pathology. In appraising their role, we aim at suggesting a paradigm shift based on the available clinical and experimental data that will be discussed. Taste and olfaction are polymodal sensory systems, providing inputs to many brain structures that regulate crucial visceral functions, including metabolism but also endocrine, cardiovascular, respiratory, and immune systems. Moreover, other visceral chemosensory systems monitor different essential chemical parameters of “milieu intérieur,” transmitting their data to the brain areas receiving taste and olfactory inputs; hence, they participate in regulating the same vital functions. These chemosensory cells share many molecular features with olfactory or taste receptor cells, thus they may be affected by the same pathological events. In most COVID-19 patients, taste and olfaction are disturbed. This may represent only a small portion of a broadly diffuse chemosensory incapacitation. Indeed, many COVID-19 peculiar symptoms may be explained by the impairment of visceral chemosensory systems, for example, silent hypoxia, diarrhea, and the “cytokine storm”. Dysregulation of chemosensory systems may underlie the much higher mortality rate of COVID-19 Acute Respiratory Distress Syndrome (ARDS) compared to ARDSs of different origins. In chronic non-infectious diseases like hypertension, diabetes, or cancer, the impairment of taste and/or olfaction has been consistently reported. This may signal diffuse chemosensory failure, possibly worsening the prognosis of these patients. Incapacitation of one or few chemosensory systems has negligible effects on survival under ordinary life conditions but, under stress, like metabolic imbalance or COVID-19 pneumonia, the impairment of multiple chemosensory systems may lead to dire consequences during the course of the disease.

How β cells can smell insulin fragments

In this issue of Cell Metabolism, Cheng et al. identify olfactory receptor Olfr109 in β cells with increased expression in islets from mouse models of obesity and type 1 and type 2 diabetes. Binding of a small insulin fragment to Olfr109 fosters islet inflammation, β cell failure, and diabetes progression.