Díaz-Hernandez Miguel, del Puerto Ana, Díaz-Hernandez Juan Ignacio, Diez-Zaera María, Lucas José Javier, Garrido Juan José, Miras-Portugal María Teresa
Departamento de Bioquímica y Biología Molecular IV, Facultad de Veterinaria, UCM, 28040-Madrid, Spain.
J Cell Sci. 2008 Nov 15;121(Pt 22):3717-28. doi: 10.1242/jcs.034082.
During the establishment of neural circuits, the axons of neurons grow towards their target regions in response to both positive and negative stimuli. Because recent reports show that Ca2+ transients in growth cones negatively regulate axonal growth, we studied how ionotropic ATP receptors (P2X) might participate in this process. Our results show that exposing cultured hippocampal neurons to ATP induces Ca2+ transients in the distal domain of the axon and the concomitant inhibition of axonal growth. This effect is mediated by the P2X7 receptor, which is present in the growth cone of the axon. Pharmacological inhibition of P2X7 or its silencing by shRNA interference induces longer and more-branched axons, coupled with morphological changes to the growth cone. Our data suggest that these morphological changes are induced by a signalling cascade in which CaMKII and FAK activity activates PI3-kinase and modifies the activity of its downstream targets. Thus, in the absence or inactivation of P2X7 receptor, axons grow more rapidly and form more branches in cultured hippocampal neurons, indicative that ATP exerts a negative influence on axonal growth. These data suggest that P2X7 antagonists have therapeutic potential to promote axonal regeneration.
在神经回路建立过程中，神经元轴突会响应正负刺激向其靶区域生长。由于最近的报道显示生长锥中的Ca2+瞬变对轴突生长具有负调控作用，我们研究了离子型ATP受体（P2X）可能如何参与这一过程。我们的结果表明，将培养的海马神经元暴露于ATP会在轴突远端区域诱导Ca2+瞬变，并伴随轴突生长的抑制。这种效应由P2X7受体介导，该受体存在于轴突的生长锥中。对P2X7进行药理抑制或通过shRNA干扰使其沉默会诱导轴突更长且分支更多，同时生长锥的形态也会发生变化。我们的数据表明，这些形态变化是由一个信号级联反应诱导的，其中CaMKII和FAK活性激活PI3激酶并改变其下游靶点的活性。因此，在P2X7受体缺失或失活的情况下，培养的海马神经元中的轴突生长更快且形成更多分支，这表明ATP对轴突生长具有负面影响。这些数据表明P2X7拮抗剂具有促进轴突再生的治疗潜力。
