Mechanisms of endoplasmic reticulum export of the glycine transporter GLYT1

Enrique Fernández-Sánchez , F Javier Díez-Guerra , Beatriz Cubelos , Cecilio Giménez , Francisco Zafra (1)

1 CBMSO - Centro de Biología Molecular Severo Ochoa [Madrid]

The glycine transporter GLYT1 regulates both glycinergic and glutamatergic neurotransmission by controlling the reuptake of glycine at synapses. Trafficking to the cell surface of GLYT1 is critical for its function. In this article, by using mutational analysis of the GLYT1 C-terminal domain we identified the evolutionary conserved motif R 575}L 576}(X8)D 585} as being necessary for endoplasmic reticulum (ER) export. This is probably due to its capacity to bind Sec24D, a component of the COPII complex. This ER export motif was active when introduced into the related GLYT2 transporter but not in the unrelated VSVG protein. GLYT1 protein in which this motif was mutated was not transported to the plasma membrane, although this effect was rescued by co-expressing these mutants with wild-type GLYT1. This behavior suggests that GLYT1 might form oligomers along the trafficking pathway. Cross-linking assays performed in rat brain synaptosomes, and Fluorescence Resonance Energy Transfer (FRET) microscopy in living cells confirmed the existence of GLYT1 oligomers. In summary, we have identified a motif involved in the ER exit of GLYT1 and in analyzing the influence of this motif, we have found evidence that oligomerization is important for the trafficking of GLYT1 to the cell surface. Because this motif is conserved in the NSS family, it is possible that this finding could be extrapolated to other related transporters.

Mots clés: Life Sciences

Enrique Fernández-Sánchez, F Javier Díez-Guerra, Beatriz Cubelos, Cecilio Giménez, Francisco Zafra. Mechanisms of endoplasmic reticulum export of the glycine transporter GLYT1. Biochemical Journal, 2007, 409 (3), pp.669-681. ⟨10.1042/BJ20070533⟩. ⟨hal-00478789⟩