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CD36 is involved in oleic acid detection by the murine olfactory system.

Oberland S, Ackels T, Gaab S, Pelz T, Spehr J, Spehr M, Neuhaus EM - Front Cell Neurosci (2015)

Bottom Line: In accordance with the described roles of CD36 as fatty acid receptor or co-receptor in other sensory systems, the number of olfactory neurons responding to oleic acid, a major milk component, in Ca(2+) imaging experiments is drastically reduced in young CD36 knock-out mice.Strikingly, we also observe marked age-dependent changes in CD36 localization, which is prominently present in the ciliary compartment only during the suckling period.Our results support the involvement of CD36 in fatty acid detection by the mammalian olfactory system.

View Article: PubMed Central - PubMed

Affiliation: Pharmacology and Toxicology, University Hospital Jena, Friedrich-Schiller-University Jena Jena, Germany ; Cluster of Excellence NeuroCure, Charité-Universitätsmedizin Berlin Berlin, Germany ; Freie Universität-Berlin, Fachbereich Biologie, Chemie und Pharmazie Berlin, Germany.

ABSTRACT
Olfactory signals influence food intake in a variety of species. To maximize the chances of finding a source of calories, an animal's preference for fatty foods and triglycerides already becomes apparent during olfactory food search behavior. However, the molecular identity of both receptors and ligands mediating olfactory-dependent fatty acid recognition are, so far, undescribed. We here describe that a subset of olfactory sensory neurons expresses the fatty acid receptor CD36 and demonstrate a receptor-like localization of CD36 in olfactory cilia by STED microscopy. CD36-positive olfactory neurons share olfaction-specific transduction elements and project to numerous glomeruli in the ventral olfactory bulb. In accordance with the described roles of CD36 as fatty acid receptor or co-receptor in other sensory systems, the number of olfactory neurons responding to oleic acid, a major milk component, in Ca(2+) imaging experiments is drastically reduced in young CD36 knock-out mice. Strikingly, we also observe marked age-dependent changes in CD36 localization, which is prominently present in the ciliary compartment only during the suckling period. Our results support the involvement of CD36 in fatty acid detection by the mammalian olfactory system.

No MeSH data available.


Related in: MedlinePlus

CD36 is expressed in the olfactory epithelium. (A) Quantitative real-time PCR showing expression of CD36 in adult mice compared to two olfactory receptors (mOR-EG and Olfr124). Data are the mean of five mice (n = 5) and three technical replicates each. Significance was calculated using two sample t-test. Error bars represent SEM (*p ≤ 0.05). (B) Western blot analysis of whole olfactory epithelium preparation, membrane preparation and supernatant of membrane preparation of an adult mouse showing CD36 protein expression. (C) Confocal image of a cryosection (P8) immunostained for CD36 (green) and the mature olfactory neuron marker OMP (red). CD36 is present in soma, dendrite and knob. (D) Confocal image (maximum projection) of an adult vomeronasal organ cryosection immunostained for OMP (red) and CD36 (green) showing densely packed vomeronasal sensory neurons but no CD36 presence in these neurons. (E) Confocal image of a cryosection (P8) immunostained for CD36 (green) and the mature olfactory neuron marker OMP (red) in CD36−/− mice, showing absence of labeling. (F,G) Single channels of the picture shown in (E). (H) RNA in situ hybridization of wild-type P8 cryosection showing CD36 mRNA expression in OSNs. (I) RNA in situ hybridization of cryosection from CD36−/− mouse showing the absence of CD36 mRNA. Scale bars: 5 μm (C), 20 μm (D), 20 μm (E), 50 μm (H), 50 μm (I).
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Figure 1: CD36 is expressed in the olfactory epithelium. (A) Quantitative real-time PCR showing expression of CD36 in adult mice compared to two olfactory receptors (mOR-EG and Olfr124). Data are the mean of five mice (n = 5) and three technical replicates each. Significance was calculated using two sample t-test. Error bars represent SEM (*p ≤ 0.05). (B) Western blot analysis of whole olfactory epithelium preparation, membrane preparation and supernatant of membrane preparation of an adult mouse showing CD36 protein expression. (C) Confocal image of a cryosection (P8) immunostained for CD36 (green) and the mature olfactory neuron marker OMP (red). CD36 is present in soma, dendrite and knob. (D) Confocal image (maximum projection) of an adult vomeronasal organ cryosection immunostained for OMP (red) and CD36 (green) showing densely packed vomeronasal sensory neurons but no CD36 presence in these neurons. (E) Confocal image of a cryosection (P8) immunostained for CD36 (green) and the mature olfactory neuron marker OMP (red) in CD36−/− mice, showing absence of labeling. (F,G) Single channels of the picture shown in (E). (H) RNA in situ hybridization of wild-type P8 cryosection showing CD36 mRNA expression in OSNs. (I) RNA in situ hybridization of cryosection from CD36−/− mouse showing the absence of CD36 mRNA. Scale bars: 5 μm (C), 20 μm (D), 20 μm (E), 50 μm (H), 50 μm (I).

Mentions: We detected CD36 in olfactory epithelia of mice by previous proteomic analysis (Rasche et al., 2010), CD36 protein has also been found to be highly abundant in the proteome of rat cilia (Mayer et al., 2009). We therefore analyzed the expression pattern of CD36 in the olfactory system. Quantitative real-time PCR revealed that the expression level of CD36 was significantly higher compared to olfactory receptors Olfr73 (mOR-EG) and Olfr124 (CD36: 0.161, mOR-EG: 0.009, Olfr124: 0.003; Figure 1A), similar as the protein amounts detected in previous proteomic approaches. We also detected the described 88 kD glycosylated form of CD36 protein (Talle et al., 1983; Abumrad et al., 1993; Han et al., 1997) by western blot analysis of whole olfactory epithelium and of olfactory epithelium membrane preparations, but not in the supernatant fraction containing soluble cytosolic proteins (Figure 1B).


CD36 is involved in oleic acid detection by the murine olfactory system.

Oberland S, Ackels T, Gaab S, Pelz T, Spehr J, Spehr M, Neuhaus EM - Front Cell Neurosci (2015)

CD36 is expressed in the olfactory epithelium. (A) Quantitative real-time PCR showing expression of CD36 in adult mice compared to two olfactory receptors (mOR-EG and Olfr124). Data are the mean of five mice (n = 5) and three technical replicates each. Significance was calculated using two sample t-test. Error bars represent SEM (*p ≤ 0.05). (B) Western blot analysis of whole olfactory epithelium preparation, membrane preparation and supernatant of membrane preparation of an adult mouse showing CD36 protein expression. (C) Confocal image of a cryosection (P8) immunostained for CD36 (green) and the mature olfactory neuron marker OMP (red). CD36 is present in soma, dendrite and knob. (D) Confocal image (maximum projection) of an adult vomeronasal organ cryosection immunostained for OMP (red) and CD36 (green) showing densely packed vomeronasal sensory neurons but no CD36 presence in these neurons. (E) Confocal image of a cryosection (P8) immunostained for CD36 (green) and the mature olfactory neuron marker OMP (red) in CD36−/− mice, showing absence of labeling. (F,G) Single channels of the picture shown in (E). (H) RNA in situ hybridization of wild-type P8 cryosection showing CD36 mRNA expression in OSNs. (I) RNA in situ hybridization of cryosection from CD36−/− mouse showing the absence of CD36 mRNA. Scale bars: 5 μm (C), 20 μm (D), 20 μm (E), 50 μm (H), 50 μm (I).
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Figure 1: CD36 is expressed in the olfactory epithelium. (A) Quantitative real-time PCR showing expression of CD36 in adult mice compared to two olfactory receptors (mOR-EG and Olfr124). Data are the mean of five mice (n = 5) and three technical replicates each. Significance was calculated using two sample t-test. Error bars represent SEM (*p ≤ 0.05). (B) Western blot analysis of whole olfactory epithelium preparation, membrane preparation and supernatant of membrane preparation of an adult mouse showing CD36 protein expression. (C) Confocal image of a cryosection (P8) immunostained for CD36 (green) and the mature olfactory neuron marker OMP (red). CD36 is present in soma, dendrite and knob. (D) Confocal image (maximum projection) of an adult vomeronasal organ cryosection immunostained for OMP (red) and CD36 (green) showing densely packed vomeronasal sensory neurons but no CD36 presence in these neurons. (E) Confocal image of a cryosection (P8) immunostained for CD36 (green) and the mature olfactory neuron marker OMP (red) in CD36−/− mice, showing absence of labeling. (F,G) Single channels of the picture shown in (E). (H) RNA in situ hybridization of wild-type P8 cryosection showing CD36 mRNA expression in OSNs. (I) RNA in situ hybridization of cryosection from CD36−/− mouse showing the absence of CD36 mRNA. Scale bars: 5 μm (C), 20 μm (D), 20 μm (E), 50 μm (H), 50 μm (I).
Mentions: We detected CD36 in olfactory epithelia of mice by previous proteomic analysis (Rasche et al., 2010), CD36 protein has also been found to be highly abundant in the proteome of rat cilia (Mayer et al., 2009). We therefore analyzed the expression pattern of CD36 in the olfactory system. Quantitative real-time PCR revealed that the expression level of CD36 was significantly higher compared to olfactory receptors Olfr73 (mOR-EG) and Olfr124 (CD36: 0.161, mOR-EG: 0.009, Olfr124: 0.003; Figure 1A), similar as the protein amounts detected in previous proteomic approaches. We also detected the described 88 kD glycosylated form of CD36 protein (Talle et al., 1983; Abumrad et al., 1993; Han et al., 1997) by western blot analysis of whole olfactory epithelium and of olfactory epithelium membrane preparations, but not in the supernatant fraction containing soluble cytosolic proteins (Figure 1B).

Bottom Line: In accordance with the described roles of CD36 as fatty acid receptor or co-receptor in other sensory systems, the number of olfactory neurons responding to oleic acid, a major milk component, in Ca(2+) imaging experiments is drastically reduced in young CD36 knock-out mice.Strikingly, we also observe marked age-dependent changes in CD36 localization, which is prominently present in the ciliary compartment only during the suckling period.Our results support the involvement of CD36 in fatty acid detection by the mammalian olfactory system.

View Article: PubMed Central - PubMed

Affiliation: Pharmacology and Toxicology, University Hospital Jena, Friedrich-Schiller-University Jena Jena, Germany ; Cluster of Excellence NeuroCure, Charité-Universitätsmedizin Berlin Berlin, Germany ; Freie Universität-Berlin, Fachbereich Biologie, Chemie und Pharmazie Berlin, Germany.

ABSTRACT
Olfactory signals influence food intake in a variety of species. To maximize the chances of finding a source of calories, an animal's preference for fatty foods and triglycerides already becomes apparent during olfactory food search behavior. However, the molecular identity of both receptors and ligands mediating olfactory-dependent fatty acid recognition are, so far, undescribed. We here describe that a subset of olfactory sensory neurons expresses the fatty acid receptor CD36 and demonstrate a receptor-like localization of CD36 in olfactory cilia by STED microscopy. CD36-positive olfactory neurons share olfaction-specific transduction elements and project to numerous glomeruli in the ventral olfactory bulb. In accordance with the described roles of CD36 as fatty acid receptor or co-receptor in other sensory systems, the number of olfactory neurons responding to oleic acid, a major milk component, in Ca(2+) imaging experiments is drastically reduced in young CD36 knock-out mice. Strikingly, we also observe marked age-dependent changes in CD36 localization, which is prominently present in the ciliary compartment only during the suckling period. Our results support the involvement of CD36 in fatty acid detection by the mammalian olfactory system.

No MeSH data available.


Related in: MedlinePlus