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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 localization is regulated. (A–F) Confocal images of en face olfactory epithelium preparations for age stages E18-P90 immunostained for CD36 (green) and mOR-EG (red) showing localization changes of CD36 in olfactory cilia. mOR-EG immunostainings validate successful sample preparation and show clear ciliary localization at all age stages. CD36 ciliary localization is restricted to P8 (C) and P14 (D). Before, it is found in single olfactory knobs, but barely in cilia (E18: A; P1: B) and later, ciliary localization decreases (P21: E) and is absent in adult animals (P90: F). (G) Confocal image (maximum projection) of a P90 cryosection immunostained for CD36 (green) and OMP (red). CD36 is still localized in OSN soma and denrite in adult animals. Additionally, CD36 is expressed in the microvilli layer of sustentacular cells. (H) Cell counting of CD36 and OMP expressing neurons in a stretch of 600 μm epithelium lining the septum. Cell numbers for CD36 were normalized to OMP expressing cells. If possible, both sides of every septum were counted (n = 2) to get a total number of 7–10. Significance was calculated in comparison to P8 using two sample t-test. Error bars represent SEM (*p ≤ 0.05). Scale bars, 10 μm (A–F).
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Figure 10: CD36 localization is regulated. (A–F) Confocal images of en face olfactory epithelium preparations for age stages E18-P90 immunostained for CD36 (green) and mOR-EG (red) showing localization changes of CD36 in olfactory cilia. mOR-EG immunostainings validate successful sample preparation and show clear ciliary localization at all age stages. CD36 ciliary localization is restricted to P8 (C) and P14 (D). Before, it is found in single olfactory knobs, but barely in cilia (E18: A; P1: B) and later, ciliary localization decreases (P21: E) and is absent in adult animals (P90: F). (G) Confocal image (maximum projection) of a P90 cryosection immunostained for CD36 (green) and OMP (red). CD36 is still localized in OSN soma and denrite in adult animals. Additionally, CD36 is expressed in the microvilli layer of sustentacular cells. (H) Cell counting of CD36 and OMP expressing neurons in a stretch of 600 μm epithelium lining the septum. Cell numbers for CD36 were normalized to OMP expressing cells. If possible, both sides of every septum were counted (n = 2) to get a total number of 7–10. Significance was calculated in comparison to P8 using two sample t-test. Error bars represent SEM (*p ≤ 0.05). Scale bars, 10 μm (A–F).

Mentions: As oleic acid is a major milk component, we next analyzed ciliary localization of CD36 from prenatal to adult age (Figures 10A–F). Preparations were co-immunostained for mOR-EG to ensure integrity of the tissue. CD36 was localized to a subset of olfactory knobs and cilia spreading from these. While mOR-EG was localized to cilia at all ages, clear ciliary localization of CD36 was only observed from P8-P21 (Figures 10C–E). At P21, punctate CD36 staining appeared around several olfactory knobs, indicating that CD36 labeled cilia were disintegrated. The cilia of co-stained mOR-EG expressing neurons appeared unchanged, ruling out a general disassembly or reorganization of cilia at this age (higher magnification in Supplementary Figure 1). Some regions in the epithelium even completely lacked CD36 ciliary staining at P21. Around P28, punctate labeling declined strongly as well (data not shown), and completely disappeared in older animals. Ciliary CD36 staining was lacking in P90 animals (Figure 10F). A strong, relatively uniform staining with CD36 antibodies in adult animals, however, was derived from labeled microvilli of sustentacular cells (Figure 10G and RNA in situ hybridization, data not shown). Although ciliary CD36 labeling was progressively lost between P21 and P28, CD36 was still present within somata and dendrites of single neurons until adulthood (Figure 10G). We counted the relative amount of CD36 expressing neurons among mature OMP-positive neurons from E18 to P180. Analyzing whole cryosections, we found on average ~1.6% CD36 expressing neurons (11 ± 1/677 ± 44 per section) in E18 animals, ~8.0% at P8–P14 (328 ± 29/4098 ± 436), and gradually decreasing numbers during and post-puberty (Table 1). Although we counted 161,353 sensory neurons in total (11,304 of them CD36-positive), it was not feasible to perform statistical analyses with whole slice countings, as the total number of analyzed cryosections was too low with 1–3 sections per age. For statistical analysis, we therefore defined a 600 μm epithelial stretch along the septum and quantified CD36-positive relative to OMP-positive neurons (Figure 10H). Together, the percentage of CD36 expressing neurons significantly increases after birth until P8, and decreases moderately during further aging. Nevertheless, CD36 completely disappeared from the cilia when mice were weaned. We therefore hypothesize that the presence of CD36 in cilia of olfactory neurons during the suckling period plays an important role for adaptation to the particular needs during this phase of life.


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 localization is regulated. (A–F) Confocal images of en face olfactory epithelium preparations for age stages E18-P90 immunostained for CD36 (green) and mOR-EG (red) showing localization changes of CD36 in olfactory cilia. mOR-EG immunostainings validate successful sample preparation and show clear ciliary localization at all age stages. CD36 ciliary localization is restricted to P8 (C) and P14 (D). Before, it is found in single olfactory knobs, but barely in cilia (E18: A; P1: B) and later, ciliary localization decreases (P21: E) and is absent in adult animals (P90: F). (G) Confocal image (maximum projection) of a P90 cryosection immunostained for CD36 (green) and OMP (red). CD36 is still localized in OSN soma and denrite in adult animals. Additionally, CD36 is expressed in the microvilli layer of sustentacular cells. (H) Cell counting of CD36 and OMP expressing neurons in a stretch of 600 μm epithelium lining the septum. Cell numbers for CD36 were normalized to OMP expressing cells. If possible, both sides of every septum were counted (n = 2) to get a total number of 7–10. Significance was calculated in comparison to P8 using two sample t-test. Error bars represent SEM (*p ≤ 0.05). Scale bars, 10 μm (A–F).
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Figure 10: CD36 localization is regulated. (A–F) Confocal images of en face olfactory epithelium preparations for age stages E18-P90 immunostained for CD36 (green) and mOR-EG (red) showing localization changes of CD36 in olfactory cilia. mOR-EG immunostainings validate successful sample preparation and show clear ciliary localization at all age stages. CD36 ciliary localization is restricted to P8 (C) and P14 (D). Before, it is found in single olfactory knobs, but barely in cilia (E18: A; P1: B) and later, ciliary localization decreases (P21: E) and is absent in adult animals (P90: F). (G) Confocal image (maximum projection) of a P90 cryosection immunostained for CD36 (green) and OMP (red). CD36 is still localized in OSN soma and denrite in adult animals. Additionally, CD36 is expressed in the microvilli layer of sustentacular cells. (H) Cell counting of CD36 and OMP expressing neurons in a stretch of 600 μm epithelium lining the septum. Cell numbers for CD36 were normalized to OMP expressing cells. If possible, both sides of every septum were counted (n = 2) to get a total number of 7–10. Significance was calculated in comparison to P8 using two sample t-test. Error bars represent SEM (*p ≤ 0.05). Scale bars, 10 μm (A–F).
Mentions: As oleic acid is a major milk component, we next analyzed ciliary localization of CD36 from prenatal to adult age (Figures 10A–F). Preparations were co-immunostained for mOR-EG to ensure integrity of the tissue. CD36 was localized to a subset of olfactory knobs and cilia spreading from these. While mOR-EG was localized to cilia at all ages, clear ciliary localization of CD36 was only observed from P8-P21 (Figures 10C–E). At P21, punctate CD36 staining appeared around several olfactory knobs, indicating that CD36 labeled cilia were disintegrated. The cilia of co-stained mOR-EG expressing neurons appeared unchanged, ruling out a general disassembly or reorganization of cilia at this age (higher magnification in Supplementary Figure 1). Some regions in the epithelium even completely lacked CD36 ciliary staining at P21. Around P28, punctate labeling declined strongly as well (data not shown), and completely disappeared in older animals. Ciliary CD36 staining was lacking in P90 animals (Figure 10F). A strong, relatively uniform staining with CD36 antibodies in adult animals, however, was derived from labeled microvilli of sustentacular cells (Figure 10G and RNA in situ hybridization, data not shown). Although ciliary CD36 labeling was progressively lost between P21 and P28, CD36 was still present within somata and dendrites of single neurons until adulthood (Figure 10G). We counted the relative amount of CD36 expressing neurons among mature OMP-positive neurons from E18 to P180. Analyzing whole cryosections, we found on average ~1.6% CD36 expressing neurons (11 ± 1/677 ± 44 per section) in E18 animals, ~8.0% at P8–P14 (328 ± 29/4098 ± 436), and gradually decreasing numbers during and post-puberty (Table 1). Although we counted 161,353 sensory neurons in total (11,304 of them CD36-positive), it was not feasible to perform statistical analyses with whole slice countings, as the total number of analyzed cryosections was too low with 1–3 sections per age. For statistical analysis, we therefore defined a 600 μm epithelial stretch along the septum and quantified CD36-positive relative to OMP-positive neurons (Figure 10H). Together, the percentage of CD36 expressing neurons significantly increases after birth until P8, and decreases moderately during further aging. Nevertheless, CD36 completely disappeared from the cilia when mice were weaned. We therefore hypothesize that the presence of CD36 in cilia of olfactory neurons during the suckling period plays an important role for adaptation to the particular needs during this phase of life.

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