MOLECULAR MECHANISMS OF ACTION OF DENDRONS, CONTAINING 48-60 SEQUENCE OF HIV-1 ÒÀÒ-PROTEIN, ON THE FUNCTIONAL ACTIVITY OF
THE ADENYLYL CYCLASE SIGNALING SYSTEMS
A. O. Shpakov,1 I. A. Guryanov,2 E. V. Avdeeva,3 V.I. Vorob'ev,3 G. P. Vlasov 2
1 I. M. Sechenov Institute of Evolutionary Physiology and Biochemist ó,
2 Institute of Macromolecular Compounds, and 3 Institute of Cytology RAS, St. Petersbu, Russia;
e-mail: sphakov@hormone.ief.spb.su
For the aims of studying molecular mechanisms of functioning of adenylyl cyclase signaling systems (ACS), we investigated the influence of synthetic polycationic
peptides of the star-like structure (dendrons), containing 48-60 sequence of HIV-1 TAT-protein, on the functioanal activity of ACS components in smooth muscles of the mollusc
Anodonta cygnea and in rat skeletal muscles. It has been shown that the following peptides (Gly-Arg-Lys-Lys-Arg-Arg-Gln-Arg-Arg-Arg-Pro-P o-Gln)2-Lys-eAhx
(= e-aminohexanoic acid)-Cys(Acm), referred to as peptide I, (Gly-Arg-Gly-Asp-Ser-Gly-Arg-Lys-Lys-Arg-Arg-Gln-Arg-Arg-Arg-Pro-Pro-Gln)2-Lys-sAhx-Cys(Acm) (peptide II),
[(Gly-Arg-Lys-Lys-Arg-Arg-Gln-Arg-Arg-Arg-Pro-Pro-Gln)2-Lys-eAhx-Cys]2 (peptide III), and
[(Gly-Arg Gly-Asp-Ser-Gly-Arg-Lys-Lys-Arg-Arg-Gln-Arg-Arg-Arg-Pro-Pro-Gln)2-Lys-eAhx-Cys]2 (peptide IV) inhibit in a dose-dependent manner the adenylyl cyclase (AC)
activity stimulated by both nonhormanal agents (GppNHp and forskolin) and hormones, such as serotonin (mollusc) and isoproterenol (rat). Peptides III and IV (tetrameric dendrons)
were most effective in comparison with peptides I and II (dimeric dendrons). The AC activity stimulated by hormones and forskolin was most sensitive to the action of dendrons.
All dendrons stimulated GTP-binding activity of G-proteins: dimeric dendrons were most effective at 10-5 M concentration, whereas tetrameric dendrons at 10-6 M.
In the presence of dendrons, the affinity of β-antagonist [3H]-dihydroalprenolol to β-adrenergic receptor in rat muscle membranes was unchanged. At the same
time, the affinity of β-agonist isoproterenol to the receptor decreased, and no shift to the right vas observed on the curve of isoproterenol-induced
[3H]-dihydroalprenolol displacement in the presence of GTP. The obtained data show the disturbance of the coupling between the receptor and G-protein,
which is the main reason of dendron inhibitory action on AC stimulation by hormones. Besides, these data demonstrated that hormones could disturb the functional activity of AC,
i. e. a catalytic component of ACS.
Key words: adenylyl cyclase, heterotrimeric G protein, GTP-binding, guanine nucleotide,
isoproterenol, polycationic peptid , serotonin, forskolin, TAT-protein
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