Regulation of adenylyl cyclase activity in rat testes by acylated derivatives of peptide 562–572 of a luteinizing hormone receptor

Abstract

One of directions of the search of hormonal signaling systems regulators is the development of peptides that correspond to the cytoplasmic regions of G-protein-coupled receptors (GPCR). Modification of the pepti- des with hydrophobic radicals increases their efficiency and selectivity. But currently is not studied as the acti- vity of the peptide depends on the localization of the hydrophobic radicals, their number and the chemical natu- re. The aim of this work was the synthesis of modified by fatty acid radicals derivatives of peptide 562-572 corresponding to the C-terminal region of luteinizing hormone receptor (LHR), and the study of regulatory ef- fects of the acylated LHR-peptides on the basal and hormone-stimulated activity of adenylyl cyclase (AC) in the rat tissues. To elucidate the effect of localization of hydrophobic radicals and their number the modification of peptide 562-572 only at the N- or C-terminus or at both ends was carried out. To study the effect of hydrop- hobicity the residues ofpalmitic (Pal) and decanoic (Dec) acids were selected. Using a solid phase strategy we have synthesized unmodified peptide NDTKIAKK-Nle-A562-572-KA (1) and five of its acylated analogues, such as N[K(Dec)]DTKIAKK-Nle-A562-572-KA (2), NKDTKIAKK-Nle-A562-572-[K(Dec)]A (3), N[K(Dec)] DTKIAKK-Nle-A562-572-[K(Dec)]A (4), N[K(Pal)]DTKIAKK-Nle-A562-572-KA (5), and NKDTKIAKK-Nle- A562--572-[K(Pal)]A (6). Peptide 6 modified with palmitate at the C-terminus to a large extent increased the ba- sal AC activity and reduced AC stimulating effect of human chorionic gonadotropin (hCG) in the testes of rats, peptides 3 and 4 modified with decanoate at the C-terminus were less effective, but exceeded in activity the un- modified peptide 1, while peptides 2 and 5 acylated at the N-terminus were little active. The action of peptides was characterized by the tissue and the receptor specificity. Thus, the modification of LHR-peptide 562-572 with fatty acid radicals at the C-terminus increases its regulatory effect on the functional activity of the adenyla- te cyclase system in the rat testes, indicating promising the modification of GPCR-peptides with hydrophobic radicals. These data support the hypothesis that the hydrophobic radical to be localized in the locus of GPCR-peptide, where a transmembrane domain is located in the receptor.