G Protein-Coupled Receptor Roles in Cell Migration and Cell Death Decisions

Exploring Potential Associations between Benzo[a]pyrene, Nicotine Exposure, and Lung Cancer: Molecular Insights, Prognostic Biomarkers, and Immune Cell Infiltration

Benzo[a]pyrene (BaP) and nicotine exposure have been implicated in lung cancer development. This study aims to elucidate the molecular mechanisms and potential biomarkers associated with this exposure in lung cancer patients. We integrated gene expression data from The Cancer Genome Atlas lung cancer cohort and the Comparative Toxicogenomics Database to identify differentially expressed genes (DEGs) associated with BaP and nicotine exposure. Enrichment analyses, survival analyses, and immune cell infiltration analyses were conducted to interpret the biological significance of these DEGs. A risk score model and a nomogram were constructed for a prognostic evaluation. We identified 163 DEGs related to BaP and nicotine exposure in lung cancer. Enrichment analysis revealed significant biological processes and pathways, including "IL-17 signaling", "cellular senescence", and "p53 signaling". From the DEGs, 34 prognostic genes were identified, with CLDN5, DNASE1L3, and GPR37 being independent prognostic factors. A risk score model based on these genes showed significant prognostic value, with high-risk patients exhibiting poorer survival outcomes. Additionally, a nomogram based on these risk scores demonstrated good predictive accuracy and clinical utility. Kaplan-Meier analyses confirmed that high expression of CLDN5 and GPR37 correlated with poor survival, while high DNASE1L3 expression indicated better survival. Single-gene enrichment analyses linked these genes to immune responses, cell adhesion, and DNA methylation. Immune cell infiltration analysis revealed significant correlations between the expression of these genes and the infiltration of various immune cell types. Our findings highlight the significant role of CLDN5, DNASE1L3, and GPR37 in lung cancer associated with BaP and nicotine exposure. The constructed risk score model and nomogram provide valuable tools for prognostication, and the identified genes offer potential targets for therapeutic intervention. Understanding the influence of toxic exposure on the tumor-immune microenvironment can guide future research and treatment strategies.

Regulation of CXCR4 function by S1P1 through heteromerization

BACKGROUND

The trafficking of immune cells between lymphoid organs and circulation depends on gradients of CXCL12 and sphingosine-1-phosphate (S1P), mediated through their cognate receptors C-X-C chemokine receptor type 4 (CXCR4) and S1P receptor type 1 (S1P1). S1P1 facilitates the egress of hematopoietic stem cells and lymphocytes by counteracting CXCR4-mediated retention signals. However, the molecular mechanisms underlying this interplay remain poorly understood. In this study, we uncover CXCR4-S1P1 heteromerization and explore their functional interactions.

METHODS

Bimolecular fluorescence complementation (BiFC) assay, proximity ligation assay (PLA), and quantitative bioluminescence resonance energy transfer (BRET) assay were employed to detect CXCR4-S1P1 heteromerization. Functional properties of the heteromers were assessed using cAMP assay, G protein activation, β-arrestin recruitment, ligand binding, calcium mobilization, and transwell migration assays. S1P1-overexpressing Jurkat T cells were generated via lentiviral transduction, while S1P1-deficient KARPAS299 cells and β-arrestin1/2-deficient HEK293A cells were constructed using the CRISPR/Cas9 system.

RESULTS

CXCR4-S1P1 heteromerization was observed in HEK293A cells overexpressing both receptors. The S1P/S1P1 axis interfered with CXCR4-mediated signaling, while CXCR4 did not affect S1P1-mediated signaling, indicating a unidirectional modulation of CXCR4 by S1P1. CXCL12 binding to CXCR4 remained unchanged in the presence of S1P1, and interference of CXCL12-induced Gαi activation by S1P1 was observed in β-arrestin1/2-deficient cells. BRET analysis revealed that S1P1 interfered with CXCR4-Gαi pre-association and CXCR4 oligomerization, both of which are critical for CXCR4 function. Domain-swapping experiments identified transmembrane domain 3 of S1P1 as essential for this modulation. In Jurkat T cells overexpressing S1P1, CXCR4-mediated signaling and cell migration were diminished, whereas these functions were enhanced in S1P1-deficient KARPAS299 cells. Co-activation of S1P1 attenuated CXCL12-induced migration, while pretreatment with S1P or FTY720-phosphate increased CXCR4-mediated migration by downregulating surface S1P1 in KARPAS299 cells. In primary T cells, PLA confirmed CXCR4-S1P1 heteromerization, and S1P interfered with CXCL12-induced migration.

CONCLUSIONS

This study identifies CXCR4-S1P1 heteromers and demonstrates a unidirectional modulation of CXCR4 by S1P1. S1P1 affects CXCR4 function by disrupting its G protein pre-association and oligomerization. These findings underscore the regulatory role of the S1P/S1P1 axis in CXCR4 signaling within the heteromeric context and provide novel insights into the intricate mechanisms governing immune cell trafficking.

The Role and Mechanism of Retinol and Its Transformation Product, Retinoic Acid, in Modulating Oxidative Stress-Induced Damage to the Duck Intestinal Epithelial Barrier In Vitro

This study aimed to investigate the effects and mechanisms of retinol and retinoic acid on primary duck intestinal epithelial cells under oxidative stress induced by H2O2. Different ratios of retinol and retinoic acid were used for treatment. The study evaluated the cell morphology, viability, antioxidative capacity, and barrier function of cells. The expression of genes related to oxidative stress and the intestinal barrier was analyzed. The main findings demonstrated that the treated duck intestinal epithelial cells exhibited increased viability, increased antioxidative capacity, and improved intestinal barrier function compared to the control group. High retinoic acid treatment improved viability and gene expression, while high retinol increased antioxidative indicators and promoted intestinal barrier repair. Transcriptome analysis revealed the effects of treatments on cytokine interactions, retinol metabolism, PPAR signaling, and cell adhesion. In conclusion, this study highlights the potential of retinol and retinoic acid in protecting and improving intestinal cell health under oxidative stress, providing valuable insights for future research.

Opsin3 Downregulation Induces Apoptosis of Human Epidermal Melanocytes via Mitochondrial Pathway

G protein‐coupled receptors (GPCRs) are core switches connecting excellular survival or death signals with cellular signaling pathways in a context‐dependent manner. Opsin 3 (OPN3) belongs to the GPCR superfamily. However, whether OPN3 can control the survival or death of human melanocytes is not known. Here, we try to investigate the inherent function of OPN3 on the survival of melanocytes. Our results demonstrate that OPN3 knockdown by RNAi‐OPN3 in human epidermal melanocytes leads to cell apoptosis. The downregulation of OPN3 markedly reduces intracellular calcium levels and decreases phosphorylation of BAD. Attenuated BAD phosphorylation and elevated BAD protein level alter mitochondria membrane permeability, which trigger activation of BAX and inhibition of BCL‐2 and raf‐1. Activated BAX results in the release of cytochrome c and the loss of mitochondrial membrane potential. Cytochrome c complexes associate with caspase 9, forming a postmitochondrial apoptosome that activate effector caspases including caspase 3 and caspase 7. The release of apoptotic molecules eventually promotes the occurrence of apoptosis. In conclusion, we hereby are the first to prove that OPN3 is a key signal responsible for cell survival through a calcium‐dependent G protein‐coupled signaling and mitochondrial pathway.

An evolutionarily conserved arginine is essential for Tre1 G protein-coupled receptor function during germ cell migration in Drosophila melanogaster

BACKGROUND

G protein-coupled receptors (GPCRs) play central roles in mediating cellular responses to environmental signals leading to changes in cell physiology and behaviors, including cell migration. Numerous clinical pathologies including metastasis, an invasive form of cell migration, have been linked to abnormal GPCR signaling. While the structures of some GPCRs have been defined, the in vivo roles of conserved amino acid residues and their relationships to receptor function are not fully understood. Trapped in endoderm 1 (Tre1) is an orphan receptor of the rhodopsin class that is necessary for primordial germ cell migration in Drosophila melanogaster embryos. In this study, we employ molecular genetic approaches to identify residues in Tre1 that are critical to its functions in germ cell migration.

METHODOLOGY/PRINCIPAL FINDINGS

First, we show that the previously reported scattershot mutation is an allele of tre1. The scattershot allele results in an in-frame deletion of 8 amino acids at the junction of the third transmembrane domain and the second intracellular loop of Tre1 that dramatically impairs the function of this GPCR in germ cell migration. To further refine the molecular basis for this phenotype, we assayed the effects of single amino acid substitutions in transgenic animals and determined that the arginine within the evolutionarily conserved E/N/DRY motif is critical for receptor function in mediating germ cell migration within an intact developing embryo.

CONCLUSIONS/SIGNIFICANCE

These structure-function studies of GPCR signaling in native contexts will inform future studies into the basic biology of this large and clinically important family of receptors.

Sonic hedgehog is a potent chemoattractant for human monocytes: diabetes mellitus inhibits Sonic hedgehog-induced monocyte chemotaxis

The aim of the present study was to evaluate the expression of hedgehog (Hh) signaling molecules and the chemotactic activity of Sonic hedgehog (Shh) in monocytes from control (CTR) and diabetic patients with or without coronary artery disease (CAD). Previously several studies demonstrated that exogenous administration of Shh can induce angiogenesis and accelerate repair of ischemic myocardium and skeletal muscles. Blood samples were collected from (1) CTR (n = 25); (2) patients with stable CAD without diabetes mellitus (CAD−DM, n = 10); and (3) with stable CAD with DM (CAD+DM, n = 15). Monocytes were isolated by Percoll gradient and subjected to PCR and chemotaxis analysis. Hh signaling molecules were expressed in human monocytes, and Shh-induced monocyte chemotaxis. Shh-stimulated migration of monocytes from CTR measured 172.5 ± 90% and a maximal stimulation was observed at Shh concentration of 1 μg/ml. However, Shh failed to induce migration of monocytes from CAD+DM (94.3 ± 27%, P < 0.001 vs. CTR). The impaired response to Shh was associated with strong transcriptional upregulation of the receptor Ptc, while expression of downstream molecules was not altered. Moreover, Ptc is strongly expressed in macrophages of human aortic atherosclerotic plaque. Thus, Shh is a potent chemoattractant for monocytes and it activates classical signaling pathways related to migration. The Shh signaling was negatively affected by DM which might be involved in the pathogenesis of DM-related complications.

Extra-nuclear signaling of progesterone receptor to breast cancer cell movement and invasion through the actin cytoskeleton

Progesterone plays a role in breast cancer development and progression but the effects on breast cancer cell movement or invasion have not been fully explored. In this study, we investigate the actions of natural progesterone and of the synthetic progestin medroxyprogesterone acetate (MPA) on actin cytoskeleton remodeling and on breast cancer cell movement and invasion. In particular, we characterize the nongenomic signaling cascades implicated in these actions. T47-D breast cancer cells display enhanced horizontal migration and invasion of three-dimensional matrices in the presence of both progestins. Exposure to the hormones triggers a rapid remodeling of the actin cytoskeleton and the formation of membrane ruffles required for cell movement, which are dependent on the rapid phosphorylation of the actin-regulatory protein moesin. The extra-cellular small GTPase RhoA/Rho-associated kinase (ROCK-2) cascade plays central role in progesterone- and MPA-induced moesin activation, cell migration and invasion. In the presence of progesterone, progesterone receptor A (PRA) interacts with the G protein Gα₁₃, while MPA drives PR to interact with tyrosine kinase c-Src and to activate phosphatidylinositol-3 kinase, leading to the activation of RhoA/ROCK-2. In conclusion, our findings manifest that progesterone and MPA promote breast cancer cell movement via rapid actin cytoskeleton remodeling, which are mediated by moesin activation. These events are triggered by RhoA/ROCK-2 cascade through partially differing pathways by the two compounds. These results provide original mechanistic explanations for the effects of progestins on breast cancer progression and highlight potential targets to treat endocrine-sensitive breast cancers.

A GPCR involved in post aggregation events in Dictyostelium discoideum

Dictyostelium has 55 genes encoding seven-transmembrane G-protein-coupled receptors (GPCR) that belong to five of the six GPCR families. GrlA is one of the 17 family 3 GPCRs in Dictyostelium all of which resemble GABA(B) receptors from higher eukaryotes. GrlA is a 90-kDa protein present on the plasma membrane and on membranes of the ER. It has a large extracellular domain with homology to bacterial periplasmic proteins. The GrlA message is present throughout development and shows increased levels during the post aggregation stages. Inactivation of the grlA gene does not severely affect the growth phase, however, it leads to a delay in the development at the post aggregation stage. GrlA deficient strains show an altered DIF-1 response specific to the prestalk-specific ecmA and ecmB gene, reduced car2 and pkaC transcript levels and form a reduced number of spores. Germination of the spores was as in wild type. Transcriptional profiling supported the defect in the sporulation pathway as a large number of genes involved in the biogenesis and organization of the extracellular matrix and the sporulation process were significantly downregulated in the mutant.