Further Evidence of the Melatonin Calmodulin Interaction: Effect on CaMKII Activity.

Jesús Argueta,Gloria Benítez-King,Javier Velázquez-Moctezuma,Julián Oikawa-Sala,Rosa Estrada-Reyes,Luis A Constantino-Jonapa,Héctor Solís-Chagoyán

doi:10.3390/ijms23052479

Abstract

Melatonin (MEL) is a pleiotropic indolamine that reaches multiple intracellular targets. Among these, MEL binds to calmodulin (CaM) with high affinity. In presence of Ca2+, CaM binds to CaM-dependent kinase II (CaMKII). The Ca2+-CaM/CaMKII pathway regulates a myriad of brain functions in different cellular compartments. Evidence showing the regulation of this cellular pathway by MEL is scarce. Thus, our main objective was to study the interaction of MEL with CaM and its effects on CaMKII activity in two microenvironments (aqueous and lipidic) naturally occurring within the cell. In addition, colocalization of MEL with CaM in vivo was explored in mice brain hippocampus. In vitro CaM-MEL interaction and the structural conformations of CaM in the presence of this indoleamine were assessed through electrophoretic mobility and isoelectric point. The functional consequence of this interaction was evaluated by measuring CaMKII activity. Ca2+-CaM-MEL increased the activity of CaMKII in aqueous buffer but reduced the kinase activity in lipid buffer. Importantly, MEL colocalizes in vivo with Ca2+-CaM in the hippocampus. Our evidence suggests that MEL regulates the key cellular Ca2+-CaM/CaMKII pathway and might explain why physiological MEL concentrations reduce CaMKII activity in some experimental conditions, while in others it drives biological processes through activation of this kinase.

Highlights

Melatonin (N-acetyl-5-methoxytryptamine, MEL, indoleamine) is mainly synthesized by the pineal gland reaching 10−7 M in the cerebrospinal fluid; neuronal, and glial cells synthesize MEL at specific brain regions reaching a local concentration of 10−5 M [1]
Of all the colocalization sites detected, a Pearson’s coefficient of about 0.5 or more was considered a valid colocalization site of CaM and MEL signals. These results suggest that CaM and MEL spatially overlap in mice hippocampus, and interactions between these two molecules might occur in vivo
These results suggest that CaM conformations formed in the presence of MEL in aqueous microenvironment upregulate CaM-dependent kinase II (CaMKII) activity, while those formed in the lipidic microenvironment downregulate CaMKII activity

Summary

Introduction

Melatonin (N-acetyl-5-methoxytryptamine, MEL, indoleamine) is mainly synthesized by the pineal gland (at night, dark phase) reaching 10−7 M in the cerebrospinal fluid; neuronal, and glial cells synthesize MEL at specific brain regions reaching a local concentration of 10−5 M [1]. MEL is synthesized in peripheral organs such as the skin, among others [2,3,4]. MEL binds to receptors MT1 and MT2 in the plasma membrane and to the third melatonin receptor MT3 quinone reductase in the cytosol [5]. Due to its amphiphilic nature, MEL can permeate the membrane by passive diffusion [6,7]. MEL can have a modulatory effect on some organelles, on the mitochondria, which could be related to redox and bioenergetic homeostasis [2]. MEL acts on targets such as calcium-binding proteins such as calmodulin (CaM)

Methods

Results

Discussion

Conclusion