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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

Olfactory system of CD36 knockout mice. (A,B) Widefield fluorescence microscopy images of P8 wild type (A) and CD36−/−(B) cryosections immunostained for the mature olfactory neuron marker OMP. Olfactory bulb and turbinates show no morphological abnormalities. (C,D) Head preparation of wild type (C) and CD36−/−(D) P90 animals showing no differences in OB and OE size and shape. (E) Confocal image (maximum projection) of a P8 CD36−/− cryosection immunostained for OMP (red), CD36 (green) and counterstained with TO-PRO (blue) to visualize cell nuclei. CD36 protein is absent in the olfactory epithelium. (F) Confocal image of a P14 CD36−/−en face preparation immunostained for the olfactory receptor mOR-EG. Immunostaining shows normal mOR-EG localization to olfactory knobs and cilia and unaltered ciliary length. (G–N) Confocal images (maximum projections) of wild type (G–J) and CD36−/−(K–N) cryosections immunostained for classical olfactory transduction proteins Gαolf, ACIII, CNGA2, and ANO2 (green) and counterstained with TO-PRO (blue). Signal cascade proteins are mainly restricted to the ciliary layer in both wild type and CD36−/− P8 animals and no abnormal protein distributions are observed. Scale bars: 20 μm (E,F), 50 μm (G–N), 500 μm (A,B).
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Figure 8: Olfactory system of CD36 knockout mice. (A,B) Widefield fluorescence microscopy images of P8 wild type (A) and CD36−/−(B) cryosections immunostained for the mature olfactory neuron marker OMP. Olfactory bulb and turbinates show no morphological abnormalities. (C,D) Head preparation of wild type (C) and CD36−/−(D) P90 animals showing no differences in OB and OE size and shape. (E) Confocal image (maximum projection) of a P8 CD36−/− cryosection immunostained for OMP (red), CD36 (green) and counterstained with TO-PRO (blue) to visualize cell nuclei. CD36 protein is absent in the olfactory epithelium. (F) Confocal image of a P14 CD36−/−en face preparation immunostained for the olfactory receptor mOR-EG. Immunostaining shows normal mOR-EG localization to olfactory knobs and cilia and unaltered ciliary length. (G–N) Confocal images (maximum projections) of wild type (G–J) and CD36−/−(K–N) cryosections immunostained for classical olfactory transduction proteins Gαolf, ACIII, CNGA2, and ANO2 (green) and counterstained with TO-PRO (blue). Signal cascade proteins are mainly restricted to the ciliary layer in both wild type and CD36−/− P8 animals and no abnormal protein distributions are observed. Scale bars: 20 μm (E,F), 50 μm (G–N), 500 μm (A,B).

Mentions: We further analyzed the potential role of CD36 in olfactory signaling in CD36 knockout (CD36−/−) mice (Febbraio et al., 1999). The gross anatomy of the nasal cavity and the olfactory bulb was unaltered (Figures 8A–D). Moreover, the sensory neuron morphology showed no differences compared to wild type mice (Figure 8E). We counted all OMP-positive sensory neurons in a 600 μm region of septal epithelium and detected no differences between wild type (224 neurons; n = 10 septum regions from 5 animals) and CD36−/− mice (222 neurons; n = 8 septum regions from 4 animals). Ciliary morphology of mOR-EG expressing neurons was not altered in knockout animals (Figure 8F). To determine whether the amount or the localization of signaling proteins is changed in the CD36−/− mice, we stained the olfactory epithelium for the olfactory signal transduction proteins Golf, ACIII, CNGA2, and ANO2 (Figures 8G–N) and performed quantitative PCR (data not shown). Both experiments revealed no changes in CD36−/− mice compared to wild type mice.


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)

Olfactory system of CD36 knockout mice. (A,B) Widefield fluorescence microscopy images of P8 wild type (A) and CD36−/−(B) cryosections immunostained for the mature olfactory neuron marker OMP. Olfactory bulb and turbinates show no morphological abnormalities. (C,D) Head preparation of wild type (C) and CD36−/−(D) P90 animals showing no differences in OB and OE size and shape. (E) Confocal image (maximum projection) of a P8 CD36−/− cryosection immunostained for OMP (red), CD36 (green) and counterstained with TO-PRO (blue) to visualize cell nuclei. CD36 protein is absent in the olfactory epithelium. (F) Confocal image of a P14 CD36−/−en face preparation immunostained for the olfactory receptor mOR-EG. Immunostaining shows normal mOR-EG localization to olfactory knobs and cilia and unaltered ciliary length. (G–N) Confocal images (maximum projections) of wild type (G–J) and CD36−/−(K–N) cryosections immunostained for classical olfactory transduction proteins Gαolf, ACIII, CNGA2, and ANO2 (green) and counterstained with TO-PRO (blue). Signal cascade proteins are mainly restricted to the ciliary layer in both wild type and CD36−/− P8 animals and no abnormal protein distributions are observed. Scale bars: 20 μm (E,F), 50 μm (G–N), 500 μm (A,B).
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Figure 8: Olfactory system of CD36 knockout mice. (A,B) Widefield fluorescence microscopy images of P8 wild type (A) and CD36−/−(B) cryosections immunostained for the mature olfactory neuron marker OMP. Olfactory bulb and turbinates show no morphological abnormalities. (C,D) Head preparation of wild type (C) and CD36−/−(D) P90 animals showing no differences in OB and OE size and shape. (E) Confocal image (maximum projection) of a P8 CD36−/− cryosection immunostained for OMP (red), CD36 (green) and counterstained with TO-PRO (blue) to visualize cell nuclei. CD36 protein is absent in the olfactory epithelium. (F) Confocal image of a P14 CD36−/−en face preparation immunostained for the olfactory receptor mOR-EG. Immunostaining shows normal mOR-EG localization to olfactory knobs and cilia and unaltered ciliary length. (G–N) Confocal images (maximum projections) of wild type (G–J) and CD36−/−(K–N) cryosections immunostained for classical olfactory transduction proteins Gαolf, ACIII, CNGA2, and ANO2 (green) and counterstained with TO-PRO (blue). Signal cascade proteins are mainly restricted to the ciliary layer in both wild type and CD36−/− P8 animals and no abnormal protein distributions are observed. Scale bars: 20 μm (E,F), 50 μm (G–N), 500 μm (A,B).
Mentions: We further analyzed the potential role of CD36 in olfactory signaling in CD36 knockout (CD36−/−) mice (Febbraio et al., 1999). The gross anatomy of the nasal cavity and the olfactory bulb was unaltered (Figures 8A–D). Moreover, the sensory neuron morphology showed no differences compared to wild type mice (Figure 8E). We counted all OMP-positive sensory neurons in a 600 μm region of septal epithelium and detected no differences between wild type (224 neurons; n = 10 septum regions from 5 animals) and CD36−/− mice (222 neurons; n = 8 septum regions from 4 animals). Ciliary morphology of mOR-EG expressing neurons was not altered in knockout animals (Figure 8F). To determine whether the amount or the localization of signaling proteins is changed in the CD36−/− mice, we stained the olfactory epithelium for the olfactory signal transduction proteins Golf, ACIII, CNGA2, and ANO2 (Figures 8G–N) and performed quantitative PCR (data not shown). Both experiments revealed no changes in CD36−/− mice compared to wild type mice.

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