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Astrocytic adenosine receptor A2A and Gs-coupled signaling regulate memory.

Orr AG, Hsiao EC, Wang MM, Ho K, Kim DH, Wang X, Guo W, Kang J, Yu GQ, Adame A, Devidze N, Dubal DB, Masliah E, Conklin BR, Mucke L - Nat. Neurosci. (2015)

Bottom Line: Astrocytes express a variety of G protein-coupled receptors and might influence cognitive functions, such as learning and memory.However, the roles of astrocytic Gs-coupled receptors in cognitive function are not known.Together, these findings establish a regulatory role for astrocytic Gs-coupled receptors in memory and suggest that AD-linked increases in astrocytic A2A receptor levels contribute to memory loss.

View Article: PubMed Central - PubMed

Affiliation: 1] Gladstone Institute of Neurological Disease, San Francisco, California, USA. [2] Department of Neurology, University of California, San Francisco, California, USA.

ABSTRACT
Astrocytes express a variety of G protein-coupled receptors and might influence cognitive functions, such as learning and memory. However, the roles of astrocytic Gs-coupled receptors in cognitive function are not known. We found that humans with Alzheimer's disease (AD) had increased levels of the Gs-coupled adenosine receptor A2A in astrocytes. Conditional genetic removal of these receptors enhanced long-term memory in young and aging mice and increased the levels of Arc (also known as Arg3.1), an immediate-early gene that is required for long-term memory. Chemogenetic activation of astrocytic Gs-coupled signaling reduced long-term memory in mice without affecting learning. Like humans with AD, aging mice expressing human amyloid precursor protein (hAPP) showed increased levels of astrocytic A2A receptors. Conditional genetic removal of these receptors enhanced memory in aging hAPP mice. Together, these findings establish a regulatory role for astrocytic Gs-coupled receptors in memory and suggest that AD-linked increases in astrocytic A2A receptor levels contribute to memory loss.

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Generation of GFAP-Rs1 transgenic mice(a) Representative photomicrographs of FLAG-immunostained brain sections of 2–11-month-old GFAP-tTA singly transgenic control mice (Con) and GFAP-Rs1 doubly transgenic mice. Inset: magnified view of the boxed region. Scale bars: 200 μm (left), 50 μm (right). CA3pyr: Cornu Ammonis 3 (CA3) pyramidal cell layer; CA3mol: CA3 molecular layer. n = 9 Con and 15 GFAP-Rs1 mice. (b–c) Representative photomicrographs of the hippocampal formation of GFAP-Rs1 mice immunostained for FLAG-Rs1 and astrocyte markers glutamine synthetase (GS, b) or GFAP (c). Cell nuclei were labeled with DAPI (blue). n = 6 Con and 8 GFAP-Rs1 mice. Scale bars: 50 μm. Insets (i–ii) show magnified views of the boxed regions. Inset scale bars: 25 μm.
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Figure 3: Generation of GFAP-Rs1 transgenic mice(a) Representative photomicrographs of FLAG-immunostained brain sections of 2–11-month-old GFAP-tTA singly transgenic control mice (Con) and GFAP-Rs1 doubly transgenic mice. Inset: magnified view of the boxed region. Scale bars: 200 μm (left), 50 μm (right). CA3pyr: Cornu Ammonis 3 (CA3) pyramidal cell layer; CA3mol: CA3 molecular layer. n = 9 Con and 15 GFAP-Rs1 mice. (b–c) Representative photomicrographs of the hippocampal formation of GFAP-Rs1 mice immunostained for FLAG-Rs1 and astrocyte markers glutamine synthetase (GS, b) or GFAP (c). Cell nuclei were labeled with DAPI (blue). n = 6 Con and 8 GFAP-Rs1 mice. Scale bars: 50 μm. Insets (i–ii) show magnified views of the boxed regions. Inset scale bars: 25 μm.

Mentions: To manipulate astrocytic Gs-coupled receptor signaling in adulthood in a cell- and receptor-selective manner, we generated inducible GFAP-tTA/TetO-Rs1 doubly transgenic mice (GFAP-Rs1 mice) in which astrocytic expression of a modified G -coupled receptor (Rs1)31s is regulated by a tTA/TetO system under the control of the human GFAP promoter (Supplementary Fig. 1b–c). Rs1 is the human Gs-coupled 5-HT4b serotonin receptor containing a single D100A mutation that renders it insensitive to serotonin but highly sensitive to synthetic ligands that minimally activate endogenous receptors.31 As expected, Rs1 expression was suppressed by doxycycline (DOX) in GFAP-Rs1 mice and was absent in GFAP-tTA and TetO-Rs1 singly transgenic mice (Fig. 3a and Supplementary Fig. 6a–b). We prevented Rs1 expression during development by maintaining all breeding pairs and offspring used in subsequent experiments on a DOX-supplemented diet until weaning at three weeks of age, after which DOX was removed to initiate Rs1 expression. By two months of age, Rs1 expression was detected in the hippocampal formation and thalamus (Fig. 3a and Supplementary Fig. 6a–d), but was minimal in the cortex (data not shown). Rs1 expression was selective for astrocytes, which appeared highly branched and wrapped around neuronal cell bodies (Fig. 3b–c), as is typical for this cell type.32 The proportion of astrocytes immunoreactive for Rs1 was relatively low, possibly due to low GFAP promoter activity in early adulthood.33 In the Cornu Ammonis areas of the hippocampus, 12.46 ± 1.83% of GFAP-positive cells were immunoreactive for FLAG-Rs1 (n = 16 hippocampal sections from 6 mice). Similarly sparse and astrocyte-selective transgene expression was reported for the GFAP-tTA construct when it was used in combination with a fluorescent reporter.32GFAP-Rs1 mice were viable, of normal weight, and displayed typical locomotor, exploratory, nociceptive and anxiety-related behaviors up to 19 months of age, the oldest age tested (Supplementary Fig. 6e–k).


Astrocytic adenosine receptor A2A and Gs-coupled signaling regulate memory.

Orr AG, Hsiao EC, Wang MM, Ho K, Kim DH, Wang X, Guo W, Kang J, Yu GQ, Adame A, Devidze N, Dubal DB, Masliah E, Conklin BR, Mucke L - Nat. Neurosci. (2015)

Generation of GFAP-Rs1 transgenic mice(a) Representative photomicrographs of FLAG-immunostained brain sections of 2–11-month-old GFAP-tTA singly transgenic control mice (Con) and GFAP-Rs1 doubly transgenic mice. Inset: magnified view of the boxed region. Scale bars: 200 μm (left), 50 μm (right). CA3pyr: Cornu Ammonis 3 (CA3) pyramidal cell layer; CA3mol: CA3 molecular layer. n = 9 Con and 15 GFAP-Rs1 mice. (b–c) Representative photomicrographs of the hippocampal formation of GFAP-Rs1 mice immunostained for FLAG-Rs1 and astrocyte markers glutamine synthetase (GS, b) or GFAP (c). Cell nuclei were labeled with DAPI (blue). n = 6 Con and 8 GFAP-Rs1 mice. Scale bars: 50 μm. Insets (i–ii) show magnified views of the boxed regions. Inset scale bars: 25 μm.
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Figure 3: Generation of GFAP-Rs1 transgenic mice(a) Representative photomicrographs of FLAG-immunostained brain sections of 2–11-month-old GFAP-tTA singly transgenic control mice (Con) and GFAP-Rs1 doubly transgenic mice. Inset: magnified view of the boxed region. Scale bars: 200 μm (left), 50 μm (right). CA3pyr: Cornu Ammonis 3 (CA3) pyramidal cell layer; CA3mol: CA3 molecular layer. n = 9 Con and 15 GFAP-Rs1 mice. (b–c) Representative photomicrographs of the hippocampal formation of GFAP-Rs1 mice immunostained for FLAG-Rs1 and astrocyte markers glutamine synthetase (GS, b) or GFAP (c). Cell nuclei were labeled with DAPI (blue). n = 6 Con and 8 GFAP-Rs1 mice. Scale bars: 50 μm. Insets (i–ii) show magnified views of the boxed regions. Inset scale bars: 25 μm.
Mentions: To manipulate astrocytic Gs-coupled receptor signaling in adulthood in a cell- and receptor-selective manner, we generated inducible GFAP-tTA/TetO-Rs1 doubly transgenic mice (GFAP-Rs1 mice) in which astrocytic expression of a modified G -coupled receptor (Rs1)31s is regulated by a tTA/TetO system under the control of the human GFAP promoter (Supplementary Fig. 1b–c). Rs1 is the human Gs-coupled 5-HT4b serotonin receptor containing a single D100A mutation that renders it insensitive to serotonin but highly sensitive to synthetic ligands that minimally activate endogenous receptors.31 As expected, Rs1 expression was suppressed by doxycycline (DOX) in GFAP-Rs1 mice and was absent in GFAP-tTA and TetO-Rs1 singly transgenic mice (Fig. 3a and Supplementary Fig. 6a–b). We prevented Rs1 expression during development by maintaining all breeding pairs and offspring used in subsequent experiments on a DOX-supplemented diet until weaning at three weeks of age, after which DOX was removed to initiate Rs1 expression. By two months of age, Rs1 expression was detected in the hippocampal formation and thalamus (Fig. 3a and Supplementary Fig. 6a–d), but was minimal in the cortex (data not shown). Rs1 expression was selective for astrocytes, which appeared highly branched and wrapped around neuronal cell bodies (Fig. 3b–c), as is typical for this cell type.32 The proportion of astrocytes immunoreactive for Rs1 was relatively low, possibly due to low GFAP promoter activity in early adulthood.33 In the Cornu Ammonis areas of the hippocampus, 12.46 ± 1.83% of GFAP-positive cells were immunoreactive for FLAG-Rs1 (n = 16 hippocampal sections from 6 mice). Similarly sparse and astrocyte-selective transgene expression was reported for the GFAP-tTA construct when it was used in combination with a fluorescent reporter.32GFAP-Rs1 mice were viable, of normal weight, and displayed typical locomotor, exploratory, nociceptive and anxiety-related behaviors up to 19 months of age, the oldest age tested (Supplementary Fig. 6e–k).

Bottom Line: Astrocytes express a variety of G protein-coupled receptors and might influence cognitive functions, such as learning and memory.However, the roles of astrocytic Gs-coupled receptors in cognitive function are not known.Together, these findings establish a regulatory role for astrocytic Gs-coupled receptors in memory and suggest that AD-linked increases in astrocytic A2A receptor levels contribute to memory loss.

View Article: PubMed Central - PubMed

Affiliation: 1] Gladstone Institute of Neurological Disease, San Francisco, California, USA. [2] Department of Neurology, University of California, San Francisco, California, USA.

ABSTRACT
Astrocytes express a variety of G protein-coupled receptors and might influence cognitive functions, such as learning and memory. However, the roles of astrocytic Gs-coupled receptors in cognitive function are not known. We found that humans with Alzheimer's disease (AD) had increased levels of the Gs-coupled adenosine receptor A2A in astrocytes. Conditional genetic removal of these receptors enhanced long-term memory in young and aging mice and increased the levels of Arc (also known as Arg3.1), an immediate-early gene that is required for long-term memory. Chemogenetic activation of astrocytic Gs-coupled signaling reduced long-term memory in mice without affecting learning. Like humans with AD, aging mice expressing human amyloid precursor protein (hAPP) showed increased levels of astrocytic A2A receptors. Conditional genetic removal of these receptors enhanced memory in aging hAPP mice. Together, these findings establish a regulatory role for astrocytic Gs-coupled receptors in memory and suggest that AD-linked increases in astrocytic A2A receptor levels contribute to memory loss.

Show MeSH
Related in: MedlinePlus