Receptors (Basel, Switzerland)最新文献

Background/objectives: G protein-coupled receptors (GPCRs) can promote ligand-biased signaling, yet the mechanisms that promote bias are not well understood. We have shown that C-C Chemokine Ligand 19 (CCL19) and CCL21 promote ligand-biased internalization and signaling of C-C Chemokine Receptor 7 (CCR7) in T cells. The roles of GPCR kinases (GRKs) in regulating biased CCR7 internalization and biased signaling in T cells are unclear. GRK2 is a serine/threonine kinase that phosphorylates GPCRs in response to ligand binding and is recruited to the plasma membrane via its C-terminal pleckstrin homology domain to phosphatidylinositol 4,5-bisphosphate (PIP₂).

Methods: Human embryonic kidney cells (HEK293) transfected to express wild-type and mutant GRK2 and human CCR7, human T cell lines harboring heterozygous deletions of GRK2, and naïve primary T cells from GRK2 heterozygous (GRK2^+/-) or GRK2^f/f CD4-Cre mice were used to examine the effects of GRK2 on ligand-induced CCR7 signaling in T cells. We used flow cytometry to assay the effect of GRK2 on CCR7 internalization, Fluorescence Resonance Energy Transfer (FRET) to define the effect of GRK2 on CCR7 activation of Gα_i isoforms and transwell migration assays to examine the effect of GRK2 on chemotaxis. Since chemotaxis via CCR7 is mediated by phospholipase Cγ1 (PLCγ1), Western blot assays were used to measure the effect of GRK2 during downstream signaling via phosphorylation of PLCγ1.

Results: We found that following CCL19 binding, GRK2 promoted kinase-dependent CCR7 recruitment of arrestin-3, rapid CCR7 internalization and Gα_i3 recruitment to CCR7. In contrast, following binding of CCL21 to CCR7, GRK2 slowed CCR7 internalization, induced recruitment of Gα_i2 to the activated receptor_, and promoted chemotaxis. Since we have shown that CCL21 promotes chemotaxis via PLCγ1, we examined the effect of GRK2 on PLCγ1 activation and found that GRK2 had no effect on CCL21-mediated PLCγ1 phosphorylation.

Conclusions: GRK2 promotes differential signaling downstream of CCR7 activation by CCL19 and CCL21 and provides a model for biased signaling downstream of a GPCR driven by GRK2.

Background/objectives: Gelsolin (GSN) is an actin-binding protein that helps maintain neuronal structure and shape, regulates neuronal growth, and apoptosis. Our previous work demonstrated that GSN associated with estrogen receptor beta (ERβ1) in the brains of female rats, but this association was lost in advanced age. GSN was also required for ERβ1-mediated transcriptional repression at activator protein-1 (AP-1) motifs upstream of a minimal gene promoter. However, the consequences of the loss of GSN:ERβ1 protein interaction on ERβ1 nuclear translocation and transcriptional repression at AP-1 sites located within complex endogenous gene promoters remained unclear.

Methods: We used immunofluorescent super resolution microscopy and luciferase reporter assays to test the hypothesis that GSN facilitates ERβ1 nuclear translocation and transcriptional repression of two genes relevant for Alzheimer Disease: APP (amyloid-beta precursor protein) and ITPKB (inositol-1,4,5-trisphosphate 3-kinase B).

Results: Our results revealed the novel finding that GSN is required for ERβ1 ligand-independent nuclear translocation in neuronal cells. Moreover, we show that GSN increased APP and ITPKB promoter activity, which was repressed by ERβ1.

Conclusions: Together, these data revealed the importance of the cytoskeletal protein, GSN, in regulating intracellular trafficking of nuclear receptors and demonstrate the first evidence of ERβ1 directly regulating two genes that are implicated in the progression of AD.

Background/objectives: Alzheimer's disease (AD) severely hinders cognitive function in the hippocampus (HP) and subiculum (SUB), impacting the expression of nicotinic acetylcholine receptors (nAChRs) such as the α7-subtype. To investigate α7 nAChRs as a potential PET imaging biomarker, we report the quantitative binding of [¹²⁵I]α-Bungarotoxin ([¹²⁵I]α-Bgtx) for binding to postmortem human AD (n = 29; 13 males, 16 females) HP compared to cognitively normal (CN) (n = 28; 13 male, 15 female) HP.

Methods: For comparisons with common AD biomarkers, adjacent slices were anti-Aβ and anti-Tau immunostained for analysis using QuPath.

Results: The [¹²⁵I]α-Bgtx average SUB/HP ratio was 0.5 among the CN subjects, suggesting higher [¹²⁵I]α-Bgtx binding in the HP gray matter regions. The AD subjects showed overall less binding than the CN subjects, with no statistical significance. A positive correlation was found in the [¹²⁵I]α-Bgtx binding in the AD subjects as the age increased. The Braak stage comparisons of [¹²⁵I]α-Bgtx were made with [¹⁸F]flotaza binding to Aβ plaques and [¹²⁵I]IPPI binding to Tau. A positive correlation was found between [¹²⁵I]α-Bgtx and [¹⁸F]flotaza and there was a negative correlation between [¹²⁵I]α-Bgtx and [¹²⁵I]IPPI, implicating intricate relationships between the different AD biomarkers.

Conclusions: [¹²⁵I]α-Bgtx shows complimentary potential as a α7 nAChR imaging agent but needs more preclinical assessments to confirm effectiveness for translational PET studies using α7 nAChR radioligands.

The increased prevalence of electronic cigarettes, particularly among adolescents, has escalated concerns about nicotine addiction. Nicotine, a potent psychostimulant found in tobacco products, exerts its effects by interacting with nicotinic acetylcholine receptors (nAChRs) in the brain. Recent findings in both pre-clinical and clinical studies have enhanced our understanding of nAChRs, overcoming limitations of pharmacological tools that previously hindered their investigation. Of particular interest is the α6 subunit, whose expression peaks during adolescence, a critical period of brain development often marked by the initiation of substance use. Pre-clinical studies have linked α6-containing nAChRs (α6*nAChRs) to nicotine-induced locomotion, dopamine release, and self-administration behavior. Furthermore, clinical studies suggest an association between the α6 subunit and increased smoking behavior in humans. Specifically, a single nucleotide polymorphism in the 3' untranslated region of the CHRNA6 gene that encodes for this subunit is linked to smoking behavior and other substance use. A comprehensive understanding of this subunit's role in addiction is of high importance. This review aims to consolidate current knowledge regarding the α6 subunit's functions and implications in addiction and other disorders, with the hope of paving the way for future research and the development of targeted therapies to address this pressing public health concern.

Human endocannabinoid signaling is primarily mediated by the cannabinoid receptors, CB1 and CB2, which are G protein-coupled receptors (GPCRs). These receptors have been linked to a variety of physiological processes and are being pursued as prospective drug targets due to their potential in treating pain and inflammation. However, because of their homology and shared signaling mechanisms, investigating the individual physiological roles of these receptors and designing subtype-selective ligands has been challenging. Using active-state CB1 and CB2 structures as guides, homologous residues within the orthosteric pocket of each receptor were mutated to alanine to test whether they equally impair CB1 and CB2 activity in response to two high-affinity, nonselective agonists (CP55,940 and AM12033). Interestingly, mutating the Y5.39 position impairs CB1 but not CB2 function. Conversely, mutating residue C6.47 improves CB1 but impairs CB2 signaling. TheF7.35A mutation leads to a decrease in CP55,940 potency at CB1 and impairs internalization; however, AM12033 gains potency and promotes CB1 internalization. In CB2, mutation of F7.35A decreases the potency of CP55,940 and neither agonist induces internalization. These observations provide some insight into functional sensitivity of CB1 and CB2 to different agonists when conserved residues are mutated in the orthosteric pocket.