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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 localized in olfactory cilia. (A) Confocal image of a en face preparation immunostained for CD36 showing CD36 localization in olfactory cilia (P8). (B) Higher magnification of the boxed area in (A). CD36 staining is prominent around the knob and along olfactory cilia. (C) Confocal image of an en face preparation immunostained for CD36 (green) and mOR-EG (red) showing differences in cilia length in both differently stained cell types, both proteins showed no co-expression. (D) Olfactory cilia counting: Confocal image of a top view preparation immunostained for CD36. Cilia were marked as demonstrated using a freehand tool from ImageJ. (E) Olfactory cilia counting: Confocal image of the same en face preparation shown in (C), co-immunostained for mOR-EG. (F) Total number of cilia per knob for mOR-EG-positive and CD36-positive neurons. CD36-positive cells possess half as much cilia compared to mOR-EG expressing cells. Data are shown as mean ± SEM of 55 knobs in 3 individual preparations. Significance was calculated using two sample t-test (*p ≤ 0.05). (G) Number of cilia with different length of mOR-EG-positive and CD36-positive neurons. CD36-positive cilia are shorter compared to mOR-EG-positive cilia. Data are shown as mean ± SEM of 55 knobs in 3 individual preparations. Significance was calculated using Mann–Whitney-U-Test (*p < 0.01).
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Figure 6: CD36 is localized in olfactory cilia. (A) Confocal image of a en face preparation immunostained for CD36 showing CD36 localization in olfactory cilia (P8). (B) Higher magnification of the boxed area in (A). CD36 staining is prominent around the knob and along olfactory cilia. (C) Confocal image of an en face preparation immunostained for CD36 (green) and mOR-EG (red) showing differences in cilia length in both differently stained cell types, both proteins showed no co-expression. (D) Olfactory cilia counting: Confocal image of a top view preparation immunostained for CD36. Cilia were marked as demonstrated using a freehand tool from ImageJ. (E) Olfactory cilia counting: Confocal image of the same en face preparation shown in (C), co-immunostained for mOR-EG. (F) Total number of cilia per knob for mOR-EG-positive and CD36-positive neurons. CD36-positive cells possess half as much cilia compared to mOR-EG expressing cells. Data are shown as mean ± SEM of 55 knobs in 3 individual preparations. Significance was calculated using two sample t-test (*p ≤ 0.05). (G) Number of cilia with different length of mOR-EG-positive and CD36-positive neurons. CD36-positive cilia are shorter compared to mOR-EG-positive cilia. Data are shown as mean ± SEM of 55 knobs in 3 individual preparations. Significance was calculated using Mann–Whitney-U-Test (*p < 0.01).

Mentions: Since CD36 was co-expressed with canonical signal transduction proteins, we investigated whether CD36 was also localized in olfactory cilia. We used a preparation that allows an en face view onto the epithelial surface (Oberland and Neuhaus, 2014). CD36 was localized in a subset of olfactory knobs and cilia spreading from these (Figures 6A,B), but did not co-express with the olfactory receptor mOR-EG (Figure 6C). Moreover, labeling of CD36 and mOR-EG on the same preparation revealed morphological differences between both stained cell populations. To examine these differences, we analyzed 55 CD36-positive and 55 mOR-EG-positive olfactory neurons in co-stainings (from 3 animals) by counting cilia and measuring cilia length (Figures 6D,E). We counted 14 cilia per mOR-EG expressing neuron, which is comparable to earlier scanning electron microscopy studies showing an average of 17 cilia, each up to 60 μm long (Menco et al., 1997). CD36 expressing neurons extend only half as many cilia (CD36: 7.6 ± 0.4 m, Figure 6F). Moreover, mOR-EG-positive cilia were significantly longer (Figure 6G). CD36 expressing neurons therefore seem to differ from other olfactory neurons by morphological characteristics.


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 localized in olfactory cilia. (A) Confocal image of a en face preparation immunostained for CD36 showing CD36 localization in olfactory cilia (P8). (B) Higher magnification of the boxed area in (A). CD36 staining is prominent around the knob and along olfactory cilia. (C) Confocal image of an en face preparation immunostained for CD36 (green) and mOR-EG (red) showing differences in cilia length in both differently stained cell types, both proteins showed no co-expression. (D) Olfactory cilia counting: Confocal image of a top view preparation immunostained for CD36. Cilia were marked as demonstrated using a freehand tool from ImageJ. (E) Olfactory cilia counting: Confocal image of the same en face preparation shown in (C), co-immunostained for mOR-EG. (F) Total number of cilia per knob for mOR-EG-positive and CD36-positive neurons. CD36-positive cells possess half as much cilia compared to mOR-EG expressing cells. Data are shown as mean ± SEM of 55 knobs in 3 individual preparations. Significance was calculated using two sample t-test (*p ≤ 0.05). (G) Number of cilia with different length of mOR-EG-positive and CD36-positive neurons. CD36-positive cilia are shorter compared to mOR-EG-positive cilia. Data are shown as mean ± SEM of 55 knobs in 3 individual preparations. Significance was calculated using Mann–Whitney-U-Test (*p < 0.01).
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Figure 6: CD36 is localized in olfactory cilia. (A) Confocal image of a en face preparation immunostained for CD36 showing CD36 localization in olfactory cilia (P8). (B) Higher magnification of the boxed area in (A). CD36 staining is prominent around the knob and along olfactory cilia. (C) Confocal image of an en face preparation immunostained for CD36 (green) and mOR-EG (red) showing differences in cilia length in both differently stained cell types, both proteins showed no co-expression. (D) Olfactory cilia counting: Confocal image of a top view preparation immunostained for CD36. Cilia were marked as demonstrated using a freehand tool from ImageJ. (E) Olfactory cilia counting: Confocal image of the same en face preparation shown in (C), co-immunostained for mOR-EG. (F) Total number of cilia per knob for mOR-EG-positive and CD36-positive neurons. CD36-positive cells possess half as much cilia compared to mOR-EG expressing cells. Data are shown as mean ± SEM of 55 knobs in 3 individual preparations. Significance was calculated using two sample t-test (*p ≤ 0.05). (G) Number of cilia with different length of mOR-EG-positive and CD36-positive neurons. CD36-positive cilia are shorter compared to mOR-EG-positive cilia. Data are shown as mean ± SEM of 55 knobs in 3 individual preparations. Significance was calculated using Mann–Whitney-U-Test (*p < 0.01).
Mentions: Since CD36 was co-expressed with canonical signal transduction proteins, we investigated whether CD36 was also localized in olfactory cilia. We used a preparation that allows an en face view onto the epithelial surface (Oberland and Neuhaus, 2014). CD36 was localized in a subset of olfactory knobs and cilia spreading from these (Figures 6A,B), but did not co-express with the olfactory receptor mOR-EG (Figure 6C). Moreover, labeling of CD36 and mOR-EG on the same preparation revealed morphological differences between both stained cell populations. To examine these differences, we analyzed 55 CD36-positive and 55 mOR-EG-positive olfactory neurons in co-stainings (from 3 animals) by counting cilia and measuring cilia length (Figures 6D,E). We counted 14 cilia per mOR-EG expressing neuron, which is comparable to earlier scanning electron microscopy studies showing an average of 17 cilia, each up to 60 μm long (Menco et al., 1997). CD36 expressing neurons extend only half as many cilia (CD36: 7.6 ± 0.4 m, Figure 6F). Moreover, mOR-EG-positive cilia were significantly longer (Figure 6G). CD36 expressing neurons therefore seem to differ from other olfactory neurons by morphological characteristics.

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