Reticulon RTN2B regulates trafficking and function of neuronal glutamate transporter EAAC1.
Excitatory amino acid transporters (EAATs) are the primary regulators of extracellular glutamate concentrations in the central nervous system. Their dysfunction may contribute to several neurological diseases. To date, five distinct mammalian glutamate transporters have been cloned. In brain, EAAC1 (excitatory amino acid carrier 1) is the primary neuronal glutamate transporter, localized on the perisynaptic membranes that are near release sites. Despite its potential importance in synaptic actions, little is known concerning the regulation of EAAC1 trafficking from the endoplasmic reticulum (ER) to the cell surface. Previously, we identified an EAAC1-associated protein, GTRAP3-18, an ER protein that prevents ER exit of EAAC1 when induced. Here we show that RTN2B, a member of the reticulon protein family that mainly localizes in the ER and ER exit sites interacts with EAAC1 and GTRAP3-18. EAAC1 and GTRAP3-18 bind to different regions of RTN2B. Each protein can separately and independently form complexes with EAAC1. RTN2B enhances ER exit and the cell surface composition of EAAC1 in heterologous cells. Expression of short interfering RNA-mediated knockdown of RTN2B decreases the EAAC1 protein level in neurons. Overall, our results suggest that RTN2B functions as a positive regulator in the delivery of EAAC1 from the ER to the cell surface. These studies indicate that transporter exit from the ER controlled by the interaction with its ER binding partner represents a critical regulatory step in glutamate transporter trafficking to the cell surface.
Liu
Yiting
Y
Departments of Neurology and Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, MD 21287, USA.
Vidensky
Svetlana
S
Ruggiero
Alicia M
AM
Maier
Susanne
S
Sitte
Harald H
HH
Rothstein
Jeffrey D
JD
D000818:Animals; D001921:Brain / Q000378:metabolism*; D019556:COS Cells; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism; D050580:Excitatory Amino Acid Transporter 3 / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009124:Muscle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D013569:Synapses / Q000378:metabolism
D050580:Excitatory Amino Acid Transporter 3; D008565:Membrane Proteins; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; C112025:RTN2 protein, human; C493400:SLC1A1 protein, human; C493398:Slc1a1 protein, rat; D018698:Glutamic Acid