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Functional studies and distribution define a family of transmembrane AMPA receptor regulatory proteins.

Tomita S, Chen L, Kawasaki Y, Petralia RS, Wenthold RJ, Nicoll RA, Bredt DS - J. Cell Biol. (2003)

Bottom Line: Functional expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in cerebellar granule cells requires stargazin, a member of a large family of four-pass transmembrane proteins.Here, we define a family of transmembrane AMPA receptor regulatory proteins (TARPs), which comprise stargazin, gamma-3, gamma-4, and gamma-8, but not related proteins, that mediate surface expression of AMPA receptors.These studies indicate a general role for TARPs in controlling synaptic AMPA receptors throughout the central nervous system.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of California, San Francisco, San Francisco, CA 94143, USA.

ABSTRACT
Functional expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in cerebellar granule cells requires stargazin, a member of a large family of four-pass transmembrane proteins. Here, we define a family of transmembrane AMPA receptor regulatory proteins (TARPs), which comprise stargazin, gamma-3, gamma-4, and gamma-8, but not related proteins, that mediate surface expression of AMPA receptors. TARPs exhibit discrete and complementary patterns of expression in both neurons and glia in the developing and mature central nervous system. In brain regions that express multiple isoforms, such as cerebral cortex, TARP-AMPA receptor complexes are strictly segregated, suggesting distinct roles for TARP isoforms. TARPs interact with AMPA receptors at the postsynaptic density, and surface expression of mature AMPA receptors requires a TARP. These studies indicate a general role for TARPs in controlling synaptic AMPA receptors throughout the central nervous system.

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TARPs cluster selectively at excitatory synapses that contain AMPA receptors. An antibody (pan-TARP) that reacts with all TARPs was used to stain cultured hippocampal cultures. (First row) Immunofluorescence for TARPs occurs at punctate sites (arrows) along the dendrites that closely colocalize with the GluR2 subunit of the AMPA receptor (AMPAR). (Second row) Virtually all TARP puncta colocalize with PSD-95 (arrows), but some PSD-95 puncta lack TARP immunofluorescence (arrowheads). (Third row) Almost all TARP puncta colocalize with NMDAR1 (arrows), but some NMDAR1 puncta lack TARP immunofluorescence. (Fourth row) TARPs show no overlap with the GABAergic marker GAD65. Preabsorbing the antibody with antigen (10 μM) blocks labeling (small boxes in second row).
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fig5: TARPs cluster selectively at excitatory synapses that contain AMPA receptors. An antibody (pan-TARP) that reacts with all TARPs was used to stain cultured hippocampal cultures. (First row) Immunofluorescence for TARPs occurs at punctate sites (arrows) along the dendrites that closely colocalize with the GluR2 subunit of the AMPA receptor (AMPAR). (Second row) Virtually all TARP puncta colocalize with PSD-95 (arrows), but some PSD-95 puncta lack TARP immunofluorescence (arrowheads). (Third row) Almost all TARP puncta colocalize with NMDAR1 (arrows), but some NMDAR1 puncta lack TARP immunofluorescence. (Fourth row) TARPs show no overlap with the GABAergic marker GAD65. Preabsorbing the antibody with antigen (10 μM) blocks labeling (small boxes in second row).

Mentions: To determine whether TARPs in neurons colocalize with AMPA receptors at synapses, we developed a pan-TARP antibody raised to the conserved cytosolic tail of stargazin; this antibody reacts with all four TARPs (unpublished data). Immunofluorescent labeling of primary neuronal cultures showed that TARP immunoreactivity occurs selectively at punctate sites along the dendrites (Fig. 5). These puncta reflect excitatory synapses as they overlap with AMPA receptor subunit GluR2 and with PSD-95 (Fig. 5) but not with the GABA synthesizing enzyme GAD-65 (Fig. 5). Not all excitatory (NMDA receptor–positive) synapses in cultured neurons express AMPA receptors (Gomperts et al., 1998; Liao et al., 1999), and these reflect the “silent synapses” (Isaac et al., 1995; Liao et al., 1995). Indeed, we found that TARP colocalizes with only 53 ± 16% of synapses labeled for NR1, whereas TARP colocalizes with >84 ± 6% of punctate sites labeled for GluR2 (Fig. 5).


Functional studies and distribution define a family of transmembrane AMPA receptor regulatory proteins.

Tomita S, Chen L, Kawasaki Y, Petralia RS, Wenthold RJ, Nicoll RA, Bredt DS - J. Cell Biol. (2003)

TARPs cluster selectively at excitatory synapses that contain AMPA receptors. An antibody (pan-TARP) that reacts with all TARPs was used to stain cultured hippocampal cultures. (First row) Immunofluorescence for TARPs occurs at punctate sites (arrows) along the dendrites that closely colocalize with the GluR2 subunit of the AMPA receptor (AMPAR). (Second row) Virtually all TARP puncta colocalize with PSD-95 (arrows), but some PSD-95 puncta lack TARP immunofluorescence (arrowheads). (Third row) Almost all TARP puncta colocalize with NMDAR1 (arrows), but some NMDAR1 puncta lack TARP immunofluorescence. (Fourth row) TARPs show no overlap with the GABAergic marker GAD65. Preabsorbing the antibody with antigen (10 μM) blocks labeling (small boxes in second row).
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Related In: Results  -  Collection

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fig5: TARPs cluster selectively at excitatory synapses that contain AMPA receptors. An antibody (pan-TARP) that reacts with all TARPs was used to stain cultured hippocampal cultures. (First row) Immunofluorescence for TARPs occurs at punctate sites (arrows) along the dendrites that closely colocalize with the GluR2 subunit of the AMPA receptor (AMPAR). (Second row) Virtually all TARP puncta colocalize with PSD-95 (arrows), but some PSD-95 puncta lack TARP immunofluorescence (arrowheads). (Third row) Almost all TARP puncta colocalize with NMDAR1 (arrows), but some NMDAR1 puncta lack TARP immunofluorescence. (Fourth row) TARPs show no overlap with the GABAergic marker GAD65. Preabsorbing the antibody with antigen (10 μM) blocks labeling (small boxes in second row).
Mentions: To determine whether TARPs in neurons colocalize with AMPA receptors at synapses, we developed a pan-TARP antibody raised to the conserved cytosolic tail of stargazin; this antibody reacts with all four TARPs (unpublished data). Immunofluorescent labeling of primary neuronal cultures showed that TARP immunoreactivity occurs selectively at punctate sites along the dendrites (Fig. 5). These puncta reflect excitatory synapses as they overlap with AMPA receptor subunit GluR2 and with PSD-95 (Fig. 5) but not with the GABA synthesizing enzyme GAD-65 (Fig. 5). Not all excitatory (NMDA receptor–positive) synapses in cultured neurons express AMPA receptors (Gomperts et al., 1998; Liao et al., 1999), and these reflect the “silent synapses” (Isaac et al., 1995; Liao et al., 1995). Indeed, we found that TARP colocalizes with only 53 ± 16% of synapses labeled for NR1, whereas TARP colocalizes with >84 ± 6% of punctate sites labeled for GluR2 (Fig. 5).

Bottom Line: Functional expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in cerebellar granule cells requires stargazin, a member of a large family of four-pass transmembrane proteins.Here, we define a family of transmembrane AMPA receptor regulatory proteins (TARPs), which comprise stargazin, gamma-3, gamma-4, and gamma-8, but not related proteins, that mediate surface expression of AMPA receptors.These studies indicate a general role for TARPs in controlling synaptic AMPA receptors throughout the central nervous system.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of California, San Francisco, San Francisco, CA 94143, USA.

ABSTRACT
Functional expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in cerebellar granule cells requires stargazin, a member of a large family of four-pass transmembrane proteins. Here, we define a family of transmembrane AMPA receptor regulatory proteins (TARPs), which comprise stargazin, gamma-3, gamma-4, and gamma-8, but not related proteins, that mediate surface expression of AMPA receptors. TARPs exhibit discrete and complementary patterns of expression in both neurons and glia in the developing and mature central nervous system. In brain regions that express multiple isoforms, such as cerebral cortex, TARP-AMPA receptor complexes are strictly segregated, suggesting distinct roles for TARP isoforms. TARPs interact with AMPA receptors at the postsynaptic density, and surface expression of mature AMPA receptors requires a TARP. These studies indicate a general role for TARPs in controlling synaptic AMPA receptors throughout the central nervous system.

Show MeSH
Related in: MedlinePlus