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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-positive neurons express olfactory receptors. (A) Western blot analysis of olfactory epithelium (1), membrane preparation (2), and supernatant (3) of three P60 mice showing panOR specificity to olfactory epithelium. Adult liver (4) was used as negative control; absence of GAPDH shows successful membrane preparation; mOR-EG demonstrates an olfactory receptor-specific band of same size like the panOR band. (B) Confocal image (maximum projection) of a cryosection immunostained with the panOR antibody (P8). Scale bar: 20 μm. (C–E) Confocal images (maximum projections) of a P8 cryosection immunostained for CD36 (green) and panOR (red). (F–H) Confocal images of P8 cryosections immunostained for CD36 (green) and specific olfactory receptors Olfr726 (F), Olfr71 (G), and mOR-EG (H) (red). Scale bars: 20 μm (B), 10 μm (C–H).
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Figure 5: CD36-positive neurons express olfactory receptors. (A) Western blot analysis of olfactory epithelium (1), membrane preparation (2), and supernatant (3) of three P60 mice showing panOR specificity to olfactory epithelium. Adult liver (4) was used as negative control; absence of GAPDH shows successful membrane preparation; mOR-EG demonstrates an olfactory receptor-specific band of same size like the panOR band. (B) Confocal image (maximum projection) of a cryosection immunostained with the panOR antibody (P8). Scale bar: 20 μm. (C–E) Confocal images (maximum projections) of a P8 cryosection immunostained for CD36 (green) and panOR (red). (F–H) Confocal images of P8 cryosections immunostained for CD36 (green) and specific olfactory receptors Olfr726 (F), Olfr71 (G), and mOR-EG (H) (red). Scale bars: 20 μm (B), 10 μm (C–H).

Mentions: To further analyze potential co-expression of ORs and CD36, we raised an antibody (panOR) against an amino acid sequence motif that is shared by most ORs. Similar to previous results, the non-transmembrane motif with the highest degree of conservation is MAYDRYVAIC at the transition between transmembrane domain 3 and intracellular loop 2. Although many class A GPCRs share similarity in the DRY motif, the MAY and VAIC sequences were specific for ORs and are not found in other GPCRs. Western blot analysis revealed a strong band in olfactory epithelium membrane preparations, but not in liver (Figure 5A). Immunostaining in cryosections showed labeling of the ciliary layer and many mature olfactory neurons (Figure 5B). The immunostaining partially overlapped with CD36 immunostaining: some neurons revealed strong OR and CD36 staining (Figures 5C–E). We then investigated expression of mOR-EG, Olfr71, and Olfr726 with specific antibodies, but never observed co-localization with CD36 (Figures 5F–H), indicating that individual ORs may be specifically co-expressed in CD36-positive neurons.


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-positive neurons express olfactory receptors. (A) Western blot analysis of olfactory epithelium (1), membrane preparation (2), and supernatant (3) of three P60 mice showing panOR specificity to olfactory epithelium. Adult liver (4) was used as negative control; absence of GAPDH shows successful membrane preparation; mOR-EG demonstrates an olfactory receptor-specific band of same size like the panOR band. (B) Confocal image (maximum projection) of a cryosection immunostained with the panOR antibody (P8). Scale bar: 20 μm. (C–E) Confocal images (maximum projections) of a P8 cryosection immunostained for CD36 (green) and panOR (red). (F–H) Confocal images of P8 cryosections immunostained for CD36 (green) and specific olfactory receptors Olfr726 (F), Olfr71 (G), and mOR-EG (H) (red). Scale bars: 20 μm (B), 10 μm (C–H).
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4584952&req=5

Figure 5: CD36-positive neurons express olfactory receptors. (A) Western blot analysis of olfactory epithelium (1), membrane preparation (2), and supernatant (3) of three P60 mice showing panOR specificity to olfactory epithelium. Adult liver (4) was used as negative control; absence of GAPDH shows successful membrane preparation; mOR-EG demonstrates an olfactory receptor-specific band of same size like the panOR band. (B) Confocal image (maximum projection) of a cryosection immunostained with the panOR antibody (P8). Scale bar: 20 μm. (C–E) Confocal images (maximum projections) of a P8 cryosection immunostained for CD36 (green) and panOR (red). (F–H) Confocal images of P8 cryosections immunostained for CD36 (green) and specific olfactory receptors Olfr726 (F), Olfr71 (G), and mOR-EG (H) (red). Scale bars: 20 μm (B), 10 μm (C–H).
Mentions: To further analyze potential co-expression of ORs and CD36, we raised an antibody (panOR) against an amino acid sequence motif that is shared by most ORs. Similar to previous results, the non-transmembrane motif with the highest degree of conservation is MAYDRYVAIC at the transition between transmembrane domain 3 and intracellular loop 2. Although many class A GPCRs share similarity in the DRY motif, the MAY and VAIC sequences were specific for ORs and are not found in other GPCRs. Western blot analysis revealed a strong band in olfactory epithelium membrane preparations, but not in liver (Figure 5A). Immunostaining in cryosections showed labeling of the ciliary layer and many mature olfactory neurons (Figure 5B). The immunostaining partially overlapped with CD36 immunostaining: some neurons revealed strong OR and CD36 staining (Figures 5C–E). We then investigated expression of mOR-EG, Olfr71, and Olfr726 with specific antibodies, but never observed co-localization with CD36 (Figures 5F–H), indicating that individual ORs may be specifically co-expressed in CD36-positive neurons.

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