3 research outputs found
β‑Arrestin-Biased Agonists of the GLP‑1 Receptor from β‑Amino Acid Residue Incorporation into GLP‑1 Analogues
Activation of a G protein-coupled receptor (GPCR) causes recruitment
of multiple intracellular proteins, each of which can activate distinct
signaling pathways. This complexity has engendered interest in agonists
that preferentially stimulate subsets among the natural signaling
pathways (“biased agonists”). We have examined analogues
of glucagon-like peptide-1 (GLP-1) containing β-amino acid residues
in place of native α residues at selected sites and found that
some analogues differ from GLP-1 in terms of their relative abilities
to promote G protein activation (as monitored via cAMP production)
versus β-arrestin recruitment (as monitored via BRET assays).
The α → β replacements generally cause modest declines
in stimulation of cAMP production and β-arrestin recruitment,
but for some replacement sets cAMP production is more strongly affected
than is β-arrestin recruitment. The central portion of GLP-1
appears to be critical for achieving bias toward β-arrestin
recruitment. These results suggest that backbone modification via
α → β residue replacement may be a versatile source
of agonists with biased GLP-1R activation profiles
Enhancement of α-Helix Mimicry by an α/β-Peptide Foldamer via Incorporation of a Dense Ionic Side-Chain Array
We report a new method for preorganization of α/β-peptide
helices, based on the use of a dense array of acidic and basic side
chains. Previously we have used cyclically constrained β residues
to promote α/β-peptide helicity; here we show that an
engineered ion pair array can be comparably effective, as indicated
by mimicry of the CHR domain of HIV protein gp41. The new design is
effective in biochemical and cell-based infectivity assays; however,
the resulting α/β-peptide is susceptible to proteolysis.
This susceptibility was addressed via introduction of a few cyclic
β residues near the cleavage site, to produce the most stable,
effective α/β-peptide gp41 CHR analogue identified. Crystal
structures of an α- and α/β-peptide (each involved
in a gp41-mimetic helix bundle) that contain the dense acid/base residue
array manifest disorder in the ionic side chains, but there is little
side-chain disorder in analogous α- and α/β-peptide
structures with a sparser ionic side-chain array. These observations
suggest that dense arrays of complementary acidic and basic residues
can provide conformational stabilization via Coulombic attractions
that do not require entropically costly ordering of side chains
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A Potent α/β-Peptide Analogue of GLP‑1 with Prolonged Action in Vivo
Glucagon-like peptide-1 (GLP-1) is
a natural agonist for GLP-1R,
a G protein-coupled receptor (GPCR) on the surface of pancreatic β
cells. GLP-1R agoinsts are attractive for treatment of type 2 diabetes,
but GLP-1 itself is rapidly degraded by peptidases <i>in vivo</i>. We describe a design strategy for retaining GLP-1-like activity
while engendering prolonged activity <i>in vivo</i>, based
on strategic replacement of native α residues with conformationally
constrained β-amino acid residues. This backbone-modification
approach may be useful for developing stabilized analogues of other
peptide hormones