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Binding of [ 3 H]Serotonin to Skeletal Muscle Actin
Author(s) -
Small David H.,
Wurtman Richard J.
Publication year - 1985
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1985.tb04067.x
Subject(s) - serotonin , skeletal muscle , actin , chemistry , biophysics , endocrinology , biology , biochemistry , receptor
We previously observed that the neurotransmitter 5‐hydroxytryptamine (5‐HT, serotonin) binds with high‐ and low‐affinity interactions to an actin‐like protein prepared from rat brain synaptosomes. In this study, we examined its binding to highly purified actin obtained from rabbit skeletal muscle. Monomeric G‐actin bound serotonin with high and low affinities, exhibiting equilibrium dissociation constants ( K D values) of 5 × 10 −5 M and 4 × 10 −3 M , respectively. The serotonin binding site on actin was distinct from those sites previously characterized for divalent cations, nucleotides, and cytochalasin alkaloids. The binding of serotonin (1 μ M ) to G‐actin was increased as much as 26‐fold by divalent cations. Potassium iodine (KI) increased the affinity of G‐actin for serotonin, K D values for this binding being 3 × 10 −7 M and 6 × 10 −5 M. Serotonin bound with even higher affinity to polymerized F‐actin, with K D values of 2 × 10 −8 M and 2 × 10 −5 M. However, the total number of binding sites on F‐actin was only about 4% of the number of G‐actin. The binding of serotonin (0.1 μ M ) to G‐actin could be inhibited by phenothiazines (1 μ M ) or reserpine (10 μ M ), but not by classical antagonists of serotonin receptors or by drugs that release serotonin or inhibit its uptake. The binding of serotonin to actin in vivo may participate in a contractile process related to neurotransmitter release.