The scaffolding protein PSD-95 interacts with the glycine transporter GLYT1 and impairs its internalization.
Recent evidence indicates that the glycine transporter-1 (GLYT1) plays a role in regulation of NMDA receptor function through tight control of glycine concentration in its surrounding medium. Immunohistochemical studies have demonstrated that, as well as being found in glial cells, GLYT1 is also associated with the pre- and postsynaptic aspects of glutamatergic synapses. In this article, we describe the interaction between GLYT1 and PSD-95 in the rat brain, PSD-95 being a scaffolding protein that participates in the organization of glutamatergic synapses. Mutational analysis reveals that the C-terminal sequence of GLYT1 (-SRI) is necessary for the transporter to interact with the PDZ domains I and II of PSD-95. This C-terminal tripeptide motif also seems to be involved in the trafficking of GLYT1 to the membrane, although this process does not involve PDZ proteins. GLYT1 is able to recruit PSD-95 to the plasma membrane, but it does not affect its clustering. However, the interaction stabilizes this transporter at the plasma membrane, blocking its internalization and producing a significant increase in the V(max) of glycine uptake. We hypothesize that PSD-95 might act as a scaffold for GLYT1 and NMDA receptors, allowing GLYT1 to regulate the concentrations of glycine in the micro-environment of NMDA receptors.
Cubelos
Beatriz
B
Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
González-González
Inmaculada M
IM
Giménez
Cecilio
C
Zafra
Francisco
F
D020816:Amino Acid Motifs / Q000502:physiology; D000818:Animals; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000166:cytology / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D000076122:Disks Large Homolog 4 Protein; D005455:Fluorescent Antibody Technique / Q000379:methods; D005998:Glycine / Q000378:metabolism; D050487:Glycine Plasma Membrane Transport Proteins / Q000378:metabolism*; D047468:Immunoprecipitation / Q000379:methods; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008164:Luminescent Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology*; D051381:Rats; D013997:Time Factors; D014162:Transfection / Q000379:methods; D014316:Tritium / Q000378:metabolism; D020798:Two-Hybrid System Techniques
D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D050487:Glycine Plasma Membrane Transport Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; C493266:Slc6a9 protein, rat; D014316:Tritium; D005998:Glycine