posted on 2018-12-05, 00:00authored byAlexandra Schumann-Gillett, Megan L. O’Mara
The endogenous lipids N-arachidonylglycine and
oleoyl-l-carnitine are potential therapeutic leads in the
treatment of chronic pain through their inhibition of the glycine
transporter GlyT2. However, their mechanism of action is unknown.
It has been hypothesized that these “bioactive” lipids
either inhibit GlyT2 indirectly, by significantly perturbing the biophysical
properties of the membrane, or directly, by binding directly to the
transporter (either from a membrane-exposed or solvent-exposed binding
site). Here, we used molecular dynamics simulations to study the effects
of the lipids anandamide, N-arachidonylglycine, and
oleoyl-l-carnitine on (a) the biophysical properties of the
bilayer and (b) direct binding interactions with GlyT2. During the
simulations, the biophysical properties of the bilayer itself, for
example, the area per lipid, bilayer thickness, and order parameters,
were not significantly altered by the presence or type of bioactive
lipid, regardless of the presence of GlyT2. Our work, together with
previous computational and experimental data, suggests that these
acyl-inhibitors of GlyT2 inhibit the transporter by directly binding
to it. However, these bioactive lipids bound to various parts of GlyT2
and did not prefer a single binding site during 4.5 μs of simulation.
We postulate that the binding site is located at the solvent-exposed
regions of GlyT2. Understanding the mechanism of action of these and
related bioactive lipids is essential in effectively developing high-affinity
GlyT2 inhibitors for the treatment of pain.