Development of Cell-Penetrating R7 Fragment-Conjugated Helical Peptides as Inhibitors of Estrogen Receptor-Mediated Transcription

Abstract

The heptaarginine (R7)-conjugated peptide 5 was designed and synthesized as an inhibitor of ER-coactivator interactions and ER-mediated transcription at the cellular level. The R7-conjugated peptide 5 was able to enter ER-positive T47D cells efficiently, and treatment with 3 μM of 5 downregulated the mRNA expression of pS2 (an ER-mediated gene) by 87%.

Inhibitors for the Vitamin D Receptor–Coregulator Interaction

“…Cellular activity for these peptide inhibitors was not reported until (41) developed them with a nona-arginine tag (R 9 ) that was earlier introduced by (42) as an intracellular delivery tag. PERMs with a R 9 tag were reported recently with cellular activities as low as 3 μM for the regulation of the pS2 gene expression in MCF-7 cells (43). Recently, new cyclic peptide VDR–coactivator inhibitors were introduced by (44, 45) bearing hydrocarbon linkers that have been reported to increase stability and oral bioavailability (46).…”

Structural development of stabilized helical peptides as inhibitors of estrogen receptor (ER)-mediated transcription

“…Peptides 1 and 2, both of which contained disulfide bonds, and SRC-1 (10), which contained the LXXLL coactivator motif, were prepared according to previously described methods. 8 Peptide 3, which contained an Aib residue at the 2nd position; 4, which contained an Aib residue at the 5th position; and 5, which contained Aib residues at the 2nd and 5th positions, were designed and synthesized using conventional solid phase peptide synthesis (SPPS). Furthermore, peptides 7, 8, and 9, in which a covalent C-C cross linker was present between the 2nd and 5th positions, were designed and synthesized as follows (Scheme 1): After each peptide had been elongated, it was subjected to the intramolecular ring-closing metathesis reaction on resin.…”

“…Peptides 1 and 2, which contained disulfide bridges, exhibited strong inhibitory activity (IC 50 : 35 nM for 1 (entry 1), and 13 nM for 2 (entry 2)), 8 whereas peptide 10, which contained the LXXLL coactivator motif, did not exhibit any inhibitory activity against ER-coactivator interactions (entry 10). Peptide 3, which contained an Aib(2) residue, did not inhibit ERa-coactivator interactions, even at a dose of 1000 nM (entry 3), and peptides 4, which contained an Aib(5) residue, and 5, which contained Aib(2) and Aib(5) residues, both displayed weak inhibitory activity (entries 4 and 5).…”

“…The CD spectra of peptides 1 and 2 exhibited negative maxima at around 208 and 225 nm, indicating that they formed righthanded helical structures. 8 Furthermore, the R (h 222 /h 208 ) ratios of H-Arg-Xaa d -Ile-Leu-Xaa-Arg-Npg-Leu-Gln-NH 2 (Z)-PERM-5 (8) H-Arg-Xaa-Ile-Leu-Xaa-Arg-Npg-Leu-Gln-NH 2 C-PERM-5 (9) H-Arg-Xaa-Ile-Leu-Xaa-Arg-Npg-Leu-Gln-NH 2 SRC-1 e (10) H-His-Lys-Ile-Leu-His-Arg-Leu-Leu-Gln-NH 2 a Npg: neopentylglycine. b Aib: 2-aminoisobutyric acid.…”

“…1). 8,9 As part of our ongoing research, we designed and synthesized several stabilized helical peptides containing the LXXLL motif and investigated their structural-inhibitory activity relationships. Specifically, we designed M1-PERM-4 (3), M2-PERM-4 (4), and D-PERM-4 (5), whose helical structures are stabilized by 2-aminoisobutyric acid (Aib) residues 10 rather than intramolecular disulfide bonds.…”