Toda Alyssa M A, Huganir Richard L
Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205
Proc Natl Acad Sci U S A. 2015 May 26;112(21):6712-7. doi: 10.1073/pnas.1507229112. Epub 2015 May 11.
Dynamic changes in synaptic strength are thought to be critical for higher brain function such as learning and memory. Alterations in synaptic strength can result from modulation of AMPA receptor (AMPAR) function and trafficking to synaptic sites. The phosphorylation state of AMPAR subunits is one mechanism by which cells regulate receptor function and trafficking. Receptor phosphorylation is in turn regulated by extracellular signals; these include neuronal activity, neuropeptides, and neuromodulators such as dopamine and norepinephrine (NE). Although numerous studies have reported that the neuropeptide pituitary adenylate cyclase activating polypeptide 38 (PACAP38) alters hippocampal CA1 synaptic strength and GluA1 synaptic localization, its effect on AMPAR phosphorylation state has not been explored. We determined that PACAP38 stimulation of hippocampal cultures increased phosphorylation of S845, and decreased phosphorylation of T840 on the GluA1 AMPAR subunit. Increases in GluA1 S845 phosphorylation primarily occurred via PAC1 and VPAC2 receptor activation, whereas a reduction in GluA1 T840 phosphorylation was largely driven by PAC1 receptor activation and to a lesser extent by VPAC1 and VPAC2 receptor activation. GluA1 S845 phosphorylation could be blocked by a PKA inhibitor, and GluA1 T840 dephosphorylation could be blocked by a protein phosphatase 1/2A (PP1/PP2A) inhibitor and was partly blocked by a NMDA receptor (NMDAR) antagonist. These results demonstrate that the neuropeptide PACAP38 inversely regulates the phosphorylation of two distinct sites on GluA1 and may play an important role modulating AMPAR function and synaptic plasticity in the brain.
突触强度的动态变化被认为对诸如学习和记忆等高等脑功能至关重要。突触强度的改变可能源于AMPA受体（AMPAR）功能的调节以及向突触位点的转运。AMPAR亚基的磷酸化状态是细胞调节受体功能和转运的一种机制。受体磷酸化反过来又受细胞外信号调节；这些信号包括神经元活动、神经肽以及多巴胺和去甲肾上腺素（NE）等神经调质。尽管众多研究报道神经肽垂体腺苷酸环化酶激活多肽38（PACAP38）会改变海马CA1区的突触强度和GluA1的突触定位，但其对AMPAR磷酸化状态的影响尚未得到研究。我们确定，用PACAP38刺激海马培养物会增加GluA1 AMPAR亚基上S845的磷酸化，并降低T840的磷酸化。GluA1 S845磷酸化的增加主要通过PAC1和VPAC2受体激活发生，而GluA1 T840磷酸化的降低在很大程度上由PAC1受体激活驱动，在较小程度上由VPAC1和VPAC2受体激活驱动。GluA1 S845磷酸化可被PKA抑制剂阻断，GluA1 T840去磷酸化可被蛋白磷酸酶1/2A（PP1/PP2A）抑制剂阻断，并且部分被NMDA受体（NMDAR）拮抗剂阻断。这些结果表明，神经肽PACAP38反向调节GluA1上两个不同位点的磷酸化，可能在调节大脑中AMPAR功能和突触可塑性方面发挥重要作用。
