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Molecular mechanisms involved in the adenosine A1 and A2A receptor-induced neuronal differentiation in neuroblastoma cells and striatal primary cultures (2005)

Canals, Meritxell ; Angulo, Ester ; Casadó, Vicent ; [et al.]

Oxford, UK : Blackwell Science Ltd

Journal of neurochemistry 92 (2005), S. 0

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ISSN: 1471-4159

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Medicine

Notes: Adenosine A1 receptors (A1Rs) and adenosine A2A receptors (A2ARs) are the major mediators of the neuromodulatory actions of adenosine in the brain. In the striatum A1Rs and A2ARs are mainly co-localized in the GABAergic striatopallidal neurons. In this paper we show that agonist-induced stimulation of A1Rs and A2ARs induces neurite outgrowth processes in the human neuroblastoma cell line SH-SY5Y and also in primary cultures of striatal neuronal precursor cells. The kinetics of adenosine-mediated neuritogenesis was faster than that triggered by retinoic acid. The triggering of the expression of TrkB neurotrophin receptor and the increase of cell number in the G1 phase by the activation of adenosine receptors suggest that adenosine may participate in early steps of neuronal differentiation. Furthermore, protein kinase C (PKC) and extracellular regulated kinase-1/2 (ERK-1/2) are involved in the A1R- and A2AR-mediated effects. Inhibition of protein kinase A (PKA) activity results in a total inhibition of neurite outgrowth induced by A2AR agonists but not by A1R agonists. PKA activation is therefore necessary for A2AR-mediated neuritogenesis. Co-stimulation does not lead to synergistic effects thus indicating that the neuritogenic effects of adenosine are mediated by either A1 or A2A receptors depending upon the concentration of the nucleoside. These results are relevant to understand the mechanisms by which adenosine receptors modulate neuronal differentiation and open new perspectives for considering the use of adenosine agonists as therapeutic agents in diseases requiring neuronal repair.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1471-4159.2004.02856.x

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Effect of cations on the tyrosine kinase activity of the insulin receptor: Inhibition by fluoride is magnesium dependent (1997)

Viñals, Francesc ; Camps, Marta ; Testar, Xavier ; [et al.]

Springer

Molecular and cellular biochemistry 171 (1997), S. 69-73

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ISSN: 1573-4919

Keywords: insulin receptors ; tyrosine kinase activity ; fluoride ; skeletal muscle

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Abstract We have recently reported that fluoride interacts directly with the insulin receptor, which causes inhibition of its phosphotransferase activity. The inhibitory effect of fluoride on phosphotransferase activity is not due to the formation of complexes with aluminium and occurs in the absence of alterations to the binding of ATP or insulin. In this report we substantiate that the tyrosine kinase activity of insulin receptors partially purified from rat skeletal muscle shows a strict requirement of Mg2+ ions (Ka near 11 mM). This effect of Mg2+ was inhibited in a competitive manner by Mn2+, which is compatible with competition of both divalent ions for binding sites. The inhibition of tyrosine kinase activity caused by fluoride was dependent on the concentration of Mg2+ in the medium and no inhibitory effect was detected at low concentrations of Mg2+. Moreover, the addition of increasing concentrations of Mn2+ in the presence of a constant high concentr rease in the inhibitory effect of fluoride. These results indicate that the Mg-insulin receptor complex is the major fluoride-susceptible form. Based on the characteristics of the inhibition of tyrosine kinase shown by fluoride it might be proposed that its action is exerted by the formation of multi-ionic MgF complexes analogous to Pi, which bind to the insulin receptor kinase.