Molecular Neurobiology - Universidad Autónoma de Madrid

Molecular Neurobiology
previous next
Table of contents Section contents Home Exit
D1
Glycine neurotransporters: molecular structure, biogenesis and regulation
Research summary
Our group is focused on the study of molecular mechanism, biogenesis, intracellular traffic, regulation and
pharmacology of plasma membrane glycine transporters (GLYT1 and GLYT2) that play a major role in the final
step of glycinergic transmission by removing specifically the neurotransmitter from the synapse. Our aim is to
gain insight in the physiology and pathologies associated to alterations of glycinergic neurotransmission as
neuropathic pain and muscle tone pathologies as hyperekplexia, myoclonus or epilepsia. In humans, mutations
in SLC6A5 gene (GLYT2) are the cause of autosomal sporadic hyperekplexia.
Research summary
Staff
Publications
Other activities
In collaboration with the CBMSO Bioinformatics group (A. Ramírez / A. Morreale) we have generated 3D
models for GLYT1 and GLYT2. Using molecular dynamics simulations and electrostatic calculations of the
transporters in the presence of Na + , we have identified and experimentally confirmed, the residues involved
in the additional Na + site (Na3) of GLYT2 (stoichiometry: 3Na + :1Cl - :1glycine). The replacement of Asp471
located in TM6 of GLYT2, but not the equivalent position in GLYT1 (Asp295, coupled to two Na + ), reduced Na +
affinity and cooperativity of glycine transport. An efficient allosteric communication between Asp471 and the
Na1-2 sites was inferred from the differential Na + -induced responses to tiol reagents by target cysteines in 471
(GLYT2) and 295 (GLYT1). Target cysteines show differential glycine-dependent accessibility in both isoforms.
Na + protected target cysteine from inhibition with reagent at a conformationally restricted temperature in GLYT2
but not in GLYT1, indicating direct binding to position 471.
We studied the traffic of GLYT2, which recycles between endosomes and plasma membrane through
constitutive and regulated pathways. The activation of PKC by phorbol-esters inhibits GLYT2 transport through
an increase of the internalization rate causing net accumulation of the protein in internal compartments and a
redistribution of the transporter from rafts to non-raft domains in the plasma membrane of brainstem primary
neurons and synaptosomes.
CBM 2007-2008