THE STUDY OF MOLECULAR MECHANISMS OF ACTION OF NATURAL AMINO ACIDS
AND SEROTONIN ON ADENYLYL AND GUANYLYL CYCLASES OF THE CILIATES
K.V. Derkach,1 A.O. Shpakov,1,* Z.I. Uspenskaya,1 A.L. Yudin 2
1 I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry RAS
and 2Institute of Cytology RAS, St. Petersburg;
* e-mail: alex_shpakov@list.ru
It has been previously shown that some amino acids and their derivatives are capable of regulating the activity
of adenylyl cyclase (AC) and guanylate cyclase (GC) in free-living ciliates Dileptus anser and Tetrahymena.
The aim of this work was to study the molecular mechanisms of action of methionine, tyrosine, alanine and
neurohormone serotonin on the activity of enzymes-cyclases and the identification of their specific receptors in
D. anser and T. pyriformis. Methionine and serotonin significantly increased the basal AC activity in both ciliates,
and the AC effect of serotonin in T. pyriformis was carried out with the participation of Ca2+-dependent
form of AC and heterotrimetic G proteins. AC stimulating effect of tyrosine and alanine was expressed weakly
and only detected in D. anser. Serotonin is both ciliates and alanine in D. anser stimulated GC activity, whereas
methionine and tyrosine had no effect on GC. Methionine and serotonin bind to surface receptors of the ciliates
with high affinity. KD for [methyl-3H] methionine binding to D. anser and T. pyriformis were 7.5 and 35.6 nM,
and for [3H] serotonin binding were 2.7 and 4.7 nM, respectively. Alanine and tyrosine bind to the ciliates with
low affinity. Thus, ciliates D. anser and T. pyriformis have chemosignaling systems regulated by amino acids
and their derivatives and including the enzymes with cyclase activity. There is an assumption that these systems
are similar to hormonal signaling systems of higher eukaryotes and are their predecessors.
Key words: adenylyl cyclase, amino acid, guanylyl cyclase, ciliate, methionine, receptor, serotonin, Dileptus anser, Tetrahymena pyriformis
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