Fig 3 - uploaded by Sukanya Bhowmick
Content may be subject to copyright.
Effect of sterol modulation on total phospholipid contents in cell membranes of CHO-K1 cells. Values are expressed as percentages of phospholipid in cell membranes of sterol-modulated cells relative to untreated (control) cell membranes. Data represent means ± SE of three independent experiments. See "Materials and Methods" section for other details
Source publication
The role of membrane cholesterol in modulating G protein-coupled receptor (GPCR) structure and function has emerged as a powerful theme in contemporary biology. In this paper, we report the subtlety and stringency involved in the interaction of sterols with the serotonin1A receptor. For this, we utilized two immediate biosynthetic precursors of cho...
Contexts in source publication
Context 1
... that in control cells (without MβCD) (see Fig. 2c). These results highlight the regulation of specific ligand binding activity of the serotonin 1A receptor by membrane cholesterol. In addition, these results point out the selective nature of MβCD in terms of its ability to modulate membrane cholesterol (the phospholipid content remains unchanged (Fig. ...
Context 2
... was carried out using 1 mM 7-DHC or 1 mM desmosterol (using a preformed sterol/MβCD complex (1:10, mol/mol)) (Fig. 2c). This suggests that extent of loading of 7-DHC and desmosterol was similar to what was obtained with 1 mM cholesterol (Fig. 2c). Importantly, the phospholipid content in cells remained unaltered under these conditions (Fig. 3). However, the specific agonist binding to the serotonin 1A receptor could not be restored when replenishment was carried out using 7-DHC (~ 172% of control cells, see Fig. 4), although the extent of total sterol content was comparable to control cells (Fig. 2c). We therefore conclude that 7-DHC is not capable of supporting the ligand ...
Context 3
... in the plasma membrane of macrophages ( Viswanathan et al. 2015;). As shown in Fig. 5a, treatment of control (untreated) cells with cholesterol complexed with MβCD was able to increase cholesterol level to ~ 136% of control cells. Importantly, enrichment of membrane cholesterol had no significant effect on membrane phospholipid content (Fig. 3). Next, we monitored the effect of such enrichment in cholesterol content in the plasma membrane on ligand binding function of the serotonin 1A receptor. Fig- ure 5b shows the specific agonist binding to the serotonin 1A receptor in cholesterol-enriched cells. As apparent from the figure, enrichment of cholesterol results in significant ...
Citations
... As shown in Figure 4A, we observed a significant increase in colocalization of serotonin 1A receptors with LysoTracker in these conditions. We further measured the extent of colocalization using Manders' colocalization coefficient 46 [25][26][27][28] In this work, we show that the plasma membrane population of sero- Notably, accumulation of lysosomal inclusion bodies has been reported in fibroblasts obtained from SLOS patients. 52 ...
Smith-Lemli-Opitz syndrome (SLOS) is a congenital and developmental malformation syndrome associated with defective cholesterol biosynthesis. It is characterized by accumulation of 7-dehydrocholesterol (the immediate biosynthetic precursor of cholesterol in the Kandutsch-Russell pathway) and an altered cholesterol to total sterol ratio. Since SLOS is associated with neurological malfunction, exploring the function and trafficking of neuronal receptors and their interaction with membrane lipids under these conditions assume significance. In this work, we generated a cellular model of SLOS in HEK-293 cells stably expressing the human serotonin1A receptor (an important neurotransmitter G-protein coupled receptor) using AY 9944, an inhibitor for the enzyme 3β-hydroxy-steroid-∆⁷-reductase (7-DHCR). Using a quantitative flow cytometry based assay, we show that the plasma membrane population of serotonin1A receptors was considerably reduced under these conditions without any change in total cellular expression of the receptor. Interestingly, the receptors were trafficked to sterol-enriched LysoTracker positive compartments, which accumulated under these conditions. To the best of our knowledge, our results constitute one of the first reports demonstrating intracellular accumulation and misregulated traffic of a neurotransmitter GPCR in SLOS-like conditions. We believe these results assume relevance in our overall understanding of the molecular basis underlying the functional relevance of neurotransmitter receptors in SLOS.
This article is protected by copyright. All rights reserved.
... The role of membrane cholesterol in the function of several GPCRs has been reported (6)(7)(8)(9)(10). We have previously shown that the serotonin 1A receptor, a representative class A neurotransmitter GPCR (11,12), exhibits sensitivity toward membrane cholesterol in terms of its organization, dynamics, function, and trafficking (13)(14)(15)(16)(17)(18)(19)(20)(21)(22). However, the mechanistic basis underlying the cholesterolsensitive GPCR function remains elusive. ...
... The function of several GPCRs has been shown to be intimately dependent on membrane cholesterol. For example, we have previously shown that the serotonin 1A receptor exhibits sensitivity toward membrane cholesterol in terms of its organization, dynamics, and function (13)(14)(15)(16)(17)(18)(19)(20)22). Such cholesterol dependence of GPCRs could be attributed to structural features of these receptors that could facilitate their preferential association with membrane cholesterol. ...
The function of several G protein–coupled receptors (GPCRs) exhibits cholesterol sensitivity. Cholesterol sensitivity of GPCRs could be attributed to specific sequence and structural features, such as the cholesterol recognition/interaction amino acid consensus (CRAC) motif, that facilitate their cholesterol-receptor interaction. In this work, we explored the molecular basis of cholesterol sensitivity exhibited by the serotonin 1A receptor, the most studied GPCR in the context of cholesterol sensitivity, by generating mutants of key residues in CRAC motifs in transmembrane helix 2 (TM2) and TM5 of the receptor. Our results show that a lysine residue (K101) in one of the CRAC motifs is crucial for sensing altered membrane cholesterol levels. Insights from all-atom molecular dynamics simulations showed that cholesterol-sensitive functional states of the serotonin 1A receptor are associated with reduced conformational dynamics of extracellular loops of the receptor. These results constitute one of the first reports on the molecular mechanism underlying cholesterol sensitivity of GPCRs.
... Receptor-lipid interactions are a cornerstone in receptor biology dictating receptor stability and structural dynamics. Chattopadhyay and co-workers report on the physico-chemical mechanisms underlying the interaction of sterols with GPCRs (Sarkar et al. 2020b). They have considered two immediate biosynthetic precursors of cholesterol, 7-dehydrocholesterol (7-DHC) and desmosterol, and showed that GPCR activity is sterol dependent. ...
D Vitamini Kimyasal Yapısı ve Metabolizması Hülya Cenk D Vitamini Ve Genetik Aydın Rüstemoğlu D Vitamininin Normal Serum Düzeyleri, D Vitamin Düzeylerini Etkileyen Faktörler Ve D Vitamini Yetmezliği Sabiye Akbulut Serum D Vitamininin Ölçümü Andaç Uzdoğan, Çiğdem Yücel D Vitamini Biyoyararlanımı ve Doğal Beslenme Kaynakları Atilla Çifci, Halil İbrahim Yakut Sistemik D Vitamini Tedavi Ajanları, Biyoyararlanımı ve Tedavi Yönetimi Işıl Deniz Oğuz Topikal D Vitamini Tedavisi, Tedavi Yönetimi ve Kullanıldığı Hastalıklar Dursun Türkmen Deride D Vitamini Sentezi Mekanizmaları Abdullah Demirbaş, Ömer Faruk Elmas Güneşten Koruyucu Kullanımı ve D Vitamini Nursel Dilek, Yunus Saral D Vitamininin Deri Yapısı ve Fizyolojisine Etkisi Pelin Hızlı Deri Yaşlanması ve D Vitamini Ülker Gül Psoriasis ve D Vitamini Ülker Gül Psöriatik Artrit ve D Vitamini Mehmet Uçar Atopik Dermatit ve D Vitamini Ayşegül Ertuğrul, İlknur Bostancı Mast Hücresi ve Kutanöz Mastositozda D Vitamini Selçuk Doğan, Tülin Çataklı, İlknur Bostancı Ürtiker ve D Vitamini Kemal Özyurt Kaşıntı ve D Vitamini Kübra Yüce Atamulu Likenoid Dermatozlar ve D Vitamini Nihal Altunışık Vitiligo ve D Vitamini Ayşe Akbaş Melasma ve D Vitamini İbrahim Etem Arıca Rozase ve D Vitamini Nalan Saraç Akne ve D Vitamini Selma Korkmaz Hidradenitis Süpürativa ve D Vitamini Yılmaz Ulaş Seboreik Dermatit ve D Vitamini Dilek Başaran Otoimmün Büllöz Hastalıklar ve D Vitamini Sezgi Sarıkaya Solak Bağ Doku Hastalıkları ve D Vitamini Kevser Gök Behçet Hastalığı ve D Vitamini Şule Ketenci Ertaş, Ragıp Ertaş İdiyopatik Fotodermatozlar ve D Vitamini Bülent Nuri Kalaycı İktiyozis ve D Vitamini Tubanur Çetinarslan Epidermolizis Bülloza ve Vitamin D Eda Haşal Kseroderma Pigmentozum, Epidermodisplasia Verrusiformis ve D Vitamini Derya Yayla Nevüsler ve D Vitamini Serpil Şener, Suat Sezer Aktinik Keratoz ve Seboreik Keratozda D Vitamini Mahmut Sami Metin Deri Maliniteleri ve D Vitamini Sevda Önder Vaskülitler ve Vitamin D Havva Hilal Ayvaz Venöz Trombozis ve D Vitamini Cahit Yavuz Yara İyileşmesi ve D Vitamini Bülent Nuri Kalaycı Diyabetik Ayak Ülseri ve D Vitamini Gözde Ulutaş Demirbaş, Abdullah Demirbaş Granülomatöz Hastalıklar ve D Vitamini Selma Bakar Dertlioğlu Deri Enfeksiyonları ve Vitamin D Atıl Avcı Oral Mukoza Hastalıkları ve D Vitamini Ali İhsan Güleç Tırnak Sağlığı ve Hastalıklarında D Vitamini Hülya Cenk Alopesiler ve D Vitamini Munise Daye Hirsutizm ve D Vitamini Efşan Gürbüz Yontar Sistemik Kortikosteroid Kullanımında D Vitamini Desteği Selma Korkmaz Fototerapi ve D Vitamini Tuğba Özkök Akbulut Covıd-19 Ve Vitamin D Sibel Altunışık Toplu D Vitamini Tedavisinin Yan Etkileri ve D Vitamini Tedavisi Sürecinde Dikkat Edilecek Hususlar Dursun Türkmen, Nihal Altunışık D Vitamini Ve İlaç İlaç Etkileşimleri Şule Gökşin D Vitamini İntoksikasyonu Bedriye Müge SÖNMEZ
The biosynthesis of cholesterol, an essential component of higher eukaryotic membranes, was worked out by Konrad Bloch (and Feodor Lynen) in the 1960s and they received the Nobel Prize around that time in recognition of their pioneering contributions. An elegant consequence of this was a hypothesis proposed by Konrad Bloch (the Bloch hypothesis) which suggests that each subsequent intermediate in the cholesterol biosynthesis pathway is superior in supporting membrane function in higher eukaryotes relative to its precursor. In this review, we discuss an autosomal recessive metabolic disorder, known as Smith-Lemli-Opitz syndrome (SLOS), associated with a defect in the Kandutsch-Russell pathway of cholesterol biosynthesis that results in accumulation of the immediate precursor of cholesterol in its biosynthetic pathway (7-dehydrocholesterol) and an altered cholesterol to total sterol ratio. Patients suffering from SLOS have several developmental, behavioral and cognitive abnormalities for which no drug is available yet. We characterize SLOS as a manifestation of the Bloch hypothesis and review its molecular etiology and current treatment. We further discuss defective Hedgehog signaling in SLOS and focus on the role of the serotonin1A receptor, a representative neurotransmitter receptor belonging to the GPCR family, in SLOS. Notably, ligand binding activity and cellular signaling of serotonin1A receptors are impaired in SLOS-like condition. Importantly, cellular localization and intracellular trafficking of the serotonin1A receptor (which constitute an important determinant of a GPCR cellular function) are compromised in SLOS. We highlight some of the recent developments and emerging concepts in SLOS pathobiology and suggest that novel therapies based on trafficking defects of target receptors could provide new insight into treatment of SLOS.
The interaction of lipids with G-protein-coupled receptors (GPCRs) has been shown to modulate and dictate several aspects of GPCR organization and function. Diverse lipid interaction sites have been identified from structural biology, bioinformatics, and molecular dynamics studies. For example, multiple cholesterol interaction sites have been identified in the serotonin1A receptor, along with distinct and overlapping sphingolipid interaction sites. How these lipids interact with each other and what is the resultant effect on the receptor is still not clear. In this work, we have analyzed lipid-lipid crosstalk at the receptor of the serotonin1A receptor embedded in a membrane bilayer that mimics the neuronal membrane composition by long coarse-grain simulations. Using a set of similarity coefficients, we classified lipids that bind at the receptor together as synergistic cobinding, and those that bind individually as competitive. Our results show that certain lipids interact with the serotonin1A receptor in synergy with each other. Not surprisingly, the ganglioside GM1 and cholesterol show a synergistic cobinding, along with the relatively uncommon GM1-phosphatidylethanolamine (PE) and cholesterol-PE synergy. In contrast, certain lipid pairs such as cholesterol and sphingomyelin appear to be in competition at several sites, despite their coexistence in lipid nanodomains. In addition, we observed intralipid competition between two lipid tails, with the receptor exhibiting increased interactions with the unsaturated lipid tails. We believe our work represents an important step in understanding the diversity of GPCR-lipid interactions and exploring synergistic cobinding and competition in natural membranes.
G protein-coupled receptors (GPCRs) constitute the largest class of membrane proteins that transduce signals across the plasma membrane and orchestrate a multitude of physiological processes within cells. The serotonin1A receptor is a crucial neurotransmitter receptor in the GPCR family involved in a multitude of neurological, behavioral and cognitive functions. We have previously shown, using a combination of experimental and simulation approaches, that membrane cholesterol acts as a key regulator of organization, dynamics, signaling and endocytosis of the serotonin1A receptor. In addition, we showed that membrane cholesterol stabilizes the serotonin1A receptor against thermal deactivation. In the present work, we explored the molecular basis of cholesterol-induced thermal stability of the serotonin1A receptor. For this, we explored the possible role of the K101 residue in a cholesterol recognition/interaction amino acid consensus (CRAC) motif in transmembrane helix 2 in conferring the thermal stability of the serotonin1A receptor. Our results show that a mutation in the K101 residue leads to loss in thermal stability of the serotonin1A receptor imparted by cholesterol, independent of membrane cholesterol content. We envision that our results could have potential implications in structural biological advancements of GPCRs and design of thermally stabilized receptors for drug development.
G protein-coupled receptors (GPCRs) constitute the largest class of membrane proteins that transduce signals across the plasma membrane and orchestrate a multitude of physiological processes within cells. The serotonin 1A receptor is a crucial neurotransmitter receptor in the GPCR family involved in a multitude of neurological, behavioral and cognitive functions. We have previously shown, using a combination of experimental and simulation approaches, that membrane cholesterol acts as a key regulator of organization, dynamics, signaling and endocytosis of the serotonin 1A receptor. In addition, we showed that membrane cholesterol stabilizes the serotonin 1A receptor against thermal deactivation. In the present work, we explored the molecular basis of cholesterol-induced thermal stability of the serotonin 1A receptor. For this, we explored the possible role of the K101 residue in a cholesterol recognition/interaction amino acid consensus (CRAC) motif in transmembrane helix 2 in conferring the thermal stability of the serotonin 1A receptor. Our results show that a mutation in the K101 residue leads to loss in thermal stability of the serotonin 1A receptor imparted by cholesterol, independent of membrane cholesterol content. We envision that our results could have potential implications in structural biological advancements of GPCRs and design of thermally-stabilized receptors for drug development.
