Transmembrane and ubiquitin-like domain-containing protein 1 (Tmub1/HOPS) facilitates surface expression of GluR2-containing AMPA receptors.
Some ubiquitin-like (UBL) domain-containing proteins are known to play roles in receptor trafficking. Alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs) undergo constitutive cycling between the intracellular compartment and the cell surface in the central nervous system. However, the function of UBL domain-containing proteins in the recycling of the AMPARs to the synaptic surface has not yet been reported.Here, we report that the Transmembrane and ubiquitin-like domain-containing 1 (Tmub1) protein, formerly known as the Hepatocyte Odd Protein Shuttling (HOPS) protein, which is abundantly expressed in the brain and which exists in a synaptosomal membrane fraction, facilitates the recycling of the AMPAR subunit GluR2 to the cell surface. Neurons transfected with Tmub1/HOPS-RNAi plasmids showed a significant reduction in the AMPAR current as compared to their control neurons. Consistently, the synaptic surface expression of GluR2, but not of GluR1, was significantly decreased in the neurons transfected with the Tmub1/HOPS-RNAi and increased in the neurons overexpressing EGFP-Tmub1/HOPS. The altered surface expression of GluR2 was speculated to be due to the altered surface-recycling of the internalized GluR2 in our recycling assay. Eventually, we found that GluR2 and glutamate receptor interacting protein (GRIP) were coimmunoprecipitated by the anti-Tmub1/HOPS antibody from the mouse brain. Taken together, these observations show that the Tmub1/HOPS plays a role in regulating basal synaptic transmission; it contributes to maintain the synaptic surface number of the GluR2-containing AMPARs by facilitating the recycling of GluR2 to the plasma membrane.
Yang
Hyunjeong
H
Department of Biological Information, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan.
Takagi
Hiroshi
H
Konishi
Yoshiyuki
Y
Ageta
Hiroshi
H
Ikegami
Koji
K
Yao
Ikuko
I
Sato
Showbu
S
Hatanaka
Ken
K
Inokuchi
Kaoru
K
Seog
Dae-Hyun
DH
Setou
Mitsutoshi
M
D000818:Animals; D001921:Brain / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D019295:Computational Biology / Q000379:methods; D011992:Endosomes / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000502:physiology*; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D018091:Receptors, AMPA / Q000378:metabolism / Q000502:physiology*; D013574:Synaptosomes / Q000378:metabolism; D025801:Ubiquitin / Q000737:chemistry*
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; D018091:Receptors, AMPA; D025801:Ubiquitin; C531356:HOPS protein, mouse; C104722:glutamate receptor ionotropic, AMPA 2