Biology subjects

Hanyaloglu, A. C.

Publications and source records attributed to Hanyaloglu, A. C..

8 recordsLinked to original sources

bioRxiv2025

The microbial tryptophan metabolite indole acts on the gastrointestinal tract to improve glucose homeostasis by enhancing GLP-1 secretion and L-cell differentiation

Aims/hypothesisGrowing evidence implicates gut microbiota-derived metabolites in metabolic homeostasis. Indole, a microbial tryptophan metabolite, has been reported to enhance Glucagon-like peptide-1 (GLP-1) secretion in vitro, and its derivatives have been inversely associated with risk of type 2 diabetes (T2D). We hypothesised that indole acts via the gastrointestinal tract to modulate glucose homeostasis, and aimed to test this hypothesis using in vitro and in vivo models. MethodsThe acute effects of indole on GLP-1 secretion in vitro, and on glucose tolerance and hormone secretion in mice, were determined. Subsequently, the effects of indole on intestinal epithelial cell fate and L-cell differentiation in murine ileal organoids and in vivo were studied. Finally, the utility of chronic indole administration in a murine model of T2D was explored. ResultsIndole stimulated in vitro GLP-1 secretion in a concentration-dependent manner, and improved acute glucose control in vivo. Additionally, we demonstrate that indole drives enteroendocrine L-cell differentiation in murine ileal organoids, resulting in increased L-cell density and longer-term glucoregulatory benefits in vivo. Finally, sub-chronic indole administration improved glucose tolerance and insulin sensitivity in diabetic mice. Conclusions/interpretationOur findings identify indole as an anti-diabetic molecule that acts on the gut, and raise the possibility of incorporating indole into nutraceutical supplements to aid in the treatment or prevention of T2D. This highlights the importance of gut microbiota-derived metabolites in metabolic health and opens new avenues for developing novel strategies to combat T2D. Research in ContextO_ST_ABSWhat is already known about this subject?C_ST_ABSO_LIGut microbiota-derived metabolites play a role in metabolic homeostasis. C_LIO_LIIndole, a microbial tryptophan metabolite, enhances GLP-1 secretion in vitro. C_LIO_LIIndole derivatives are inversely associated with type 2 diabetes (T2D) risk. C_LI What is the key question?O_LIDoes indole act on the gut to modulate glucose homeostasis? C_LI What are the new findings?O_LIIndole stimulates GLP-1 secretion and improves acute glucose control in vivo. C_LIO_LIIndole drives enteroendocrine L-cell differentiation in murine ileal organoids, increasing L-cell density and long-term glucoregulatory benefits. C_LIO_LISub-chronic indole administration improves glucose tolerance and insulin sensitivity in mice with type 2 diabetes, showing the potential of gut microbiota-derived metabolites as therapeutic targets. C_LI How might this impact clinical practice in the foreseeable future?O_LIIndole could be incorporated into nutraceutical supplements for T2D prevention or treatment. C_LI

physiology↗

bioRxiv2024

A spatiotemporally resolved GPCR interactome reveals novel mediators of receptor agonism

Cellular signaling by membrane G protein-coupled receptors (GPCRs) is orchestrated by a complex and diverse array of mechanisms. The dynamics of a GPCR interactome as it evolves over time and space in response to an agonist can offer a unique window on pleiotropic signaling decoding and functional selectivity at a cellular level. In this study, we employed proximity-based APEX2 proteomics to interrogate the interaction network of the GPCR for luteinizing hormone (LHR) on a minute-to-minute timescale. We developed an analytical approach integrating quantitative multiplexed proteomics and temporal reference profiles, providing a platform to identify the proteomic environment of APEX2-tagged LHR at the nanometer scale. LHR activity is exquisitely regulated at a spatial level, leading to identification of novel putative interactors including the Ras-related GTPase RAP2B that modulate both receptor signaling and post-endocytic trafficking, and providing a resource for spatiotemporal nanodomain mapping of LHR interactors across subcellular compartments. SignificanceG-protein coupled receptors (GPCRs) are the largest family of membrane proteins in the human body. GPCRs have established themselves as key drug targets, playing central roles in health and disease. The activity of this superfamily of receptors is highly dynamic, integrating diverse signaling pathways over time and across multiple subcellular compartments. Quantitative proximity proteomics using engineered ascorbate peroxidase (APEX2) has emerged as a powerful tool to map GPCR-protein interaction landscapes in both time and space. However, resolving these networks at a sub-minute timescale remains challenging, particularly for poorly characterized GPCRs with limited pharmacological tools or complex trafficking patterns. In this study, we applied APEX2 proximity proteomics to resolve at nanoscale the agonist (LH)-induced interactome of the luteinizing hormone receptor (LHR), a key GPCR in human reproduction. LHR undergoes rapid endocytosis upon LH stimulation, trafficking to a poorly understood compartment termed the very early endosome (VEE), where it engages in G protein signaling and post-endocytic sorting. Harnessing the temporal profile of GIPC1 protein, a key known interactor of LHR in the VEE pathway, we developed an analytical pipeline to identify novel endocytic interactors of LHR. Using our platform, we identified RAP2B and RAB38 as potential modulators of LHR signaling and trafficking. Overall, we present an APEX2 pipeline optimized for interrogating complex datasets, particularly for GPCRs, and potentially other membrane receptors, with limited known interactome data and minimal pharmacological tools. Our findings highlight both the complexity of GPCR interaction networks and an effective strategy to deconvolute them, providing a comprehensive resource to advance understanding of this large family of receptors. O_FIG O_LINKSMALLFIG WIDTH=199 HEIGHT=200 SRC="FIGDIR/small/599010v2_ufig1.gif" ALT="Figure 1"> View larger version (71K): org.highwire.dtl.DTLVardef@13badf7org.highwire.dtl.DTLVardef@11a5182org.highwire.dtl.DTLVardef@dd5453org.highwire.dtl.DTLVardef@cb2c27_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2024

Spatial targeting of the prostaglandin receptor EP2 to very early endosomes co-ordinates PGE2-mediated cAMP signaling in decidualizing human endometrium

Decidualization denotes the differentiation of endometrial stromal cells into specialized decidual cells, essential for embryo implantation and pregnancy. The process requires coordinated activation of both progesterone and cAMP signaling pathways, which converge on downstream transcription factors. PGE2 and relaxin, acting respectively through their Gs-coupled GPCRs EP2 and RXFP1, are putative candidates responsible for generating cAMP in differentiating stromal cells. Here, we show that PGE2 is less efficacious than relaxin in elevating intracellular cAMP levels in primary stromal cells but more effective at driving the expression of canonical decidual genes. Both PGE2- and relaxin-induced cAMP generation involves receptor internalization, but EP2 is endocytosed into very early endosomes (VEEs). Perturbation of the VEE machinery dysregulates PGE2-dependent cAMP profiles and disrupts key decidual signaling pathways, resulting in a disordered differentiation response. We demonstrate that the spatial location of EP2 is essential for coordinated activation of the downstream signaling cascades that govern decidualization.

cell biology↗

bioRxiv2022

Lack of evidence for functional luteinising hormone chorionic gonadotropin receptors in non-pregnant human endometrial stromal cells

The human luteinising hormone chorionic gonadotropin receptor (LHCGR) is a G-protein coupled receptor activated by both human chorionic gonadotropin (hCG) and luteinizing hormone (LH), two structurally related gonadotropins with essential roles in ovulation and maintenance of the corpus luteum. LHCGR expression predominates in ovarian tissues where it elicits functional responses through cyclic adenosine mononucleotide (cAMP), Ca2+ and extracellular signal-regulated kinase (ERK) signalling. LHCGR has also been localized to the human endometrium, with purported roles in decidualization and implantation. However, these observations are contentious. In this investigation, transcripts encoding LHCGR were undetectable in bulk RNA sequencing datasets from whole cycling endometrial tissue and cultured human endometrial stromal cells (EnSC). However, analysis of single-cell RNA sequencing data revealed cell-to-cell transcriptional heterogeneity and identified a small subpopulation of stromal cells with discernible LHCGR transcripts. In HEK-293 cells expressing recombinant LHCGR, both hCG and LH elicited robust cAMP, Ca2+ and ERK signals that were absent in wild type HEK-293 cells. However, none of these responses were recapitulated in primary EnSC cultures. In addition, proliferation, viability and decidual transformation of EnSC were refractory to both hCG and LH, irrespective of treatment to induce differentiation. Although we challenge the assertion that LHCGR is expressed at a functionally active level in the human endometrium, the discovery of a discrete subpopulation of EnSC that express LHCGR transcripts may plausibly account for the conflicting evidence in the literature.

pharmacology and toxicology↗

bioRxiv2021

Addition of a carboxy terminal tail to the normally tailless gonadotropin-releasing hormone receptor impairs fertility in female mice

Gonadotropin-releasing hormone (GnRH) is the primary neuropeptide controlling reproduction in vertebrates. GnRH stimulates follicle-stimulating hormone (FSH) and luteinizing hormone (LH) synthesis via a G protein-coupled receptor, GnRHR, in the pituitary gland. In mammals, GnRHR lacks a C-terminal cytosolic tail (Ctail) and does not exhibit homologous desensitization. This might be an evolutionary adaptation that enables LH surge generation and ovulation. To test this idea, we fused the chicken GnRHR Ctail to the endogenous murine GnRHR in a transgenic model. The LH surge was blunted, but not blocked in these mice. In contrast, they showed reductions in FSH production, ovarian follicle development, and fertility. Addition of the Ctail altered the nature of agonist-induced calcium signaling required for normal FSH production. The loss of the GnRHR Ctail during mammalian evolution is unlikely to have conferred a selective advantage by enabling the LH surge. The adaptive significance of this specialization remains to be determined.

physiology↗

bioRxiv2020

Short chain fatty acids enhance expression and activity of the umami taste receptor in enteroendocrine cells via a Gαi/o pathway

The short chain fatty acids (SCFAs) acetate, butyrate and propionate, are produced by the fermentation of non-digestible carbohydrates by the gut microbiota. SCFAs are of interest because they regulate appetite, adiposity, metabolism, glycemic control and immunity. SCFAs act at two distinct G protein-coupled receptors (GPCRs), FFAR2 and FFAR3. These are expressed in intestinal enteroendocrine cells (EECs), where they mediate SCFA-driven anorectic gut hormone release. EECs also express other GPCRs that act as nutrient sensors, in a manner that is plastic and adaptable to the environment. SCFAs may elicit some of their health-promoting effects by altering levels of GPCRs in EECs, thus, enhancing gut sensitivity to dietary molecules. Here, we identified that exposure of the murine EEC STC-1 cell-line to a concentration of SCFAs found in the colon, specifically enhances mRNA levels of the umami taste receptors TASR1 and TASR3, without altering levels of the SCFA GPCRs, FFAR2 and FFAR3. Interestingly, treatment of EECs with propionate or butyrate, but not acetate, increased levels of umami receptor transcripts. This phenomenon was reversed by inhibiting Gi/o signaling with pertussis toxin, suggesting that SCFAs act through FFAR2/3 to alter gene expression. Surprisingly, neither a FFAR3-nor a FFAR2-selective synthetic ligand could increase TASR1/TASR3 mRNA levels. We assessed the functional impact of increases in TASR1/TASR3 expression using unique pharmacological properties of the umami taste receptor; namely, the potentiation of signaling by inosine monophosphate. We found that the umami taste receptor induced inosine-1-phosphate and calcium signaling in response to L-alanine and L-monosodium glutamate, and that butyrate pretreatment significantly enhanced such signaling. Our study reveals that SCFAs may contribute to EEC adaptation and alter EEC sensitivity to bioactive nutrients.

cell biology↗

bioRxiv2020

Membrane estrogen receptor (GPER) and follicle-stimulating hormone receptor heteromeric complexes promote human ovarian follicle survival

Classically, follicle stimulating hormone receptor (FSHR) driven cAMP-mediated signaling boosts human ovarian follicle growth and would be essential for oocyte maturation. However, contradicting in vitro suggest a different view on physiological and clinical significance of FSHR-mediated cAMP signaling. We found that the G protein coupled estrogen receptor (GPER) heteromerizes with FSHR, reprogramming cAMP/death signals into proliferative stimuli fundamental for sustaining oocyte survival. In human granulosa cells, survival signals are effectively delivered upon equal expression levels of both receptors, while they are missing at high FSHR:GPER ratio, which negatively impacts follicle maturation and strongly correlates with FSH responsiveness of patients undergoing controlled ovarian stimulation. Consistent with high FSHR expression levels during follicular selection, cell viability is dramatically reduced in FSHR overexpressing cells due to preferential coupling to the Gs protein/cAMP pathway. In contrast, FSHR/GPER heteromer formation resulted in FSH-triggered anti-apoptotic/proliferative signaling delivered via the G{beta}{gamma} dimer while heteromer impairment or GPER-associated Gs inhibitory protein complexes resulted in cell death. GPER-depleted granulosa cells have an amplified FSH-dependent decrease in cell viability and steroidogenesis, consistent with the requirement of estrogen signaling for successful oocyte growth. Therefore, our findings indicate how oocyte maturation depends on the capability of GPER to shape FSHR selective signals, indicating hormone receptor heteromers may be a marker of cell proliferation. One Sentence SummaryFSHR/GPER heteromers block cAMP-dependent selection of ovarian follicles and target tumor growth and poor FSH-response in women.

physiology↗

bioRxiv2017

Structural lipids enable the formation of functional oligomers of the eukaryotic purine symporter UapA

The role of membrane lipids in modulating eukaryotic transporter structure and function remains poorly understood. We used native mass spectrometry in combination with molecular dynamics simulations and in vivo analyses to investigate the roles of membrane lipids in the structure and transport activity of the purine transporter, UapA, from Aspergillus nidulans. We revealed that UapA exists mainly as a dimer and that two lipid molecules bind per UapA dimer. We identified three classes of phospholipids: phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) which co-purified with UapA. Delipidation of UapA caused dissociation of the dimer into individual protomers. Subsequent addition of PI or PE rescued the UapA dimer and allowed recovery of bound lipids, suggesting a central role of these lipids in stabilising the dimer. We predicted a putative lipid-binding site near the UapA dimer interface. Mutational analyses established that lipid binding at this site is essential for formation of functional UapA dimers. Our findings reveal unprecedented level of detail into the nature of UapA-lipid interactions and provide a framework for studying similar eukaryotic systems.

biophysics↗