Differential localization and regulation of stargazin-like protein, gamma-8 and stargazin in the plasma membrane of hippocampal and cortical neurons.
Transmembrane AMPA receptor regulatory proteins (TARPs), including stargazin/gamma-2, are associated with AMPA receptors and participate in their surface delivery and anchoring at the postsynaptic membrane. TARPs may also act as a positive modulator of the AMPA receptor ion channel function; however, little is known about other TARP members except for stargazin/gamma-2. We examined the synaptic localization of stargazin/gamma-2 and gamma-8 by immunoelectron microscopy and biochemical analysis. The analysis of sodium dodecyl sulfate-digested freeze-fracture replica labeling revealed that stargazin/gamma-2 was concentrated in the postsynaptic area, whereas gamma-8 was distributed both in synaptic and extra-synaptic plasma membranes of the hippocampal neuron. When a synaptic plasma membrane-enriched brain fraction was treated with Triton X-100 and separated by sucrose density gradient ultracentrifugation, a large proportion of NMDA receptor and stargazin/gamma-2 was accumulated in raft-enriched fractions, whereas AMPA receptor and gamma-8 were distributed in both the raft-enriched fractions and other Triton-insoluble fractions. Phosphorylation of stargazin/gamma-2 and gamma-8 was regulated by different sets of kinases and phosphatases in cultured cortical neurons. These results suggested that stargazin/gamma-2 and gamma-8 have distinct roles in postsynaptic membranes under the regulation of different intracellular signaling pathways.
Inamura
Mihoko
M
Department of Anesthesiology, Kitasato University School of Medicine, Sagamihara, Kanagawa 228-8555, Japan.
Itakura
Makoto
M
Okamoto
Hirotsugu
H
Hoka
Sumio
S
Mizoguchi
Akira
A
Fukazawa
Yugo
Y
Shigemoto
Ryuichi
R
Yamamori
Saori
S
Takahashi
Masami
M
D000818:Animals; D015153:Blotting, Western / Q000379:methods; D015220:Calcium Channels / Q000145:classification / Q000378:metabolism / Q000648:ultrastructure; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005613:Freeze Etching / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000166:cytology*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D016253:Microscopy, Immunoelectron / Q000379:methods; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley
D015220:Calcium Channels; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D016202:N-Methylaspartate