The
glycine receptor is a member of the
Cys-loop receptor superfamily of
ligand-gated ion channels and is implicated as a possible therapeutic target for the treatment of diseases such as
alcoholism and inflammatory
pain. In humans, four
glycine receptor subtypes (α1, α2, α3, and β) co-assemble to form pentameric channel
proteins as either α homomers or αβ heteromers. To date, few agents have been identified that can selectively modulate the
glycine receptor, especially those possessing subtype specificity. We used a cell-based method of phage display panning, coupled with two-
electrode voltage-clamp electrophysiology in Xenopus laevis oocytes, to identify novel heptapeptide modulators of the α1β
glycine receptor. This involved a panning procedure in which the phage library initially underwent subtractive panning against Human Embryonic Kidney (HEK) 293 cells expressing alternative
glycine receptor subtypes before panning the remaining library over HEK 293 cells expressing the target, the α1β
glycine receptor.
Peptides were identified that act with selectivity on α1β and α3β, compared to α2β,
glycine receptors. In addition,
peptide activity at the
glycine receptor decreased when
zinc was chelated by
tricine, similar to previous observations of a decrease in
ethanol's enhancing actions at the receptor in the absence of
zinc. Comparisons of the amino acid sequences of heptapeptides capable of potentiating
glycine receptor function revealed several consensus sequences that may be predictive of a
peptide's enhancing ability.