Carvalho A L, Kameyama K, Huganir R L
Center for Neuroscience of Coimbra, Department of Biochemistry, University of Coimbra, 3000 Coimbra, Portugal.
J Neurosci. 1999 Jun 15;19(12):4748-54. doi: 10.1523/JNEUROSCI.19-12-04748.1999.
Recent studies have suggested that protein phosphorylation of glutamate receptors may play an important role in synaptic transmission. Specifically, the phosphorylation of AMPA receptors has been implicated in cellular models of synaptic plasticity. The phosphorylation of the glutamate receptor 1 (GluR1) subunit of AMPA receptors by protein kinase A (PKA), protein kinase C (PKC), and Ca2+/calmodulin-dependent protein kinase II (CaMKII) has been characterized extensively. Phosphorylation of this subunit occurs exclusively on the intracellular C-terminal domain. However, the GluR1 subunit C terminus shows low homology to the other AMPA receptor subunits. In this paper we characterized the phosphorylation of AMPA receptor subunit GluR4, using site-specific mutagenesis and biochemical techniques. We found that GluR4 is phosphorylated on serine 842 within the C-terminal domain in vitro and in vivo. Serine 842 is phosphorylated by PKA, PKC, and CaMKII in vitro and is phosphorylated in transfected cells by PKA. Two-dimensional phosphopeptide analysis indicates that serine 842 is the major phosphorylation site on GluR4. In addition, we identified threonine 830 as a potential PKC phosphorylation site. These results suggest that GluR4, which is the most rapidly desensitizing AMPA receptor subunit, may be modulated by phosphorylation.
最近的研究表明，谷氨酸受体的蛋白质磷酸化可能在突触传递中发挥重要作用。具体而言，AMPA受体的磷酸化已在突触可塑性的细胞模型中有所涉及。蛋白激酶A（PKA）、蛋白激酶C（PKC）和Ca2+/钙调蛋白依赖性蛋白激酶II（CaMKII）对AMPA受体的谷氨酸受体1（GluR1）亚基的磷酸化已得到广泛研究。该亚基的磷酸化仅发生在细胞内的C末端结构域。然而，GluR1亚基的C末端与其他AMPA受体亚基的同源性较低。在本文中，我们使用位点特异性诱变和生化技术对AMPA受体亚基GluR4的磷酸化进行了研究。我们发现，GluR4在体外和体内的C末端结构域内的丝氨酸842处发生磷酸化。丝氨酸842在体外可被PKA、PKC和CaMKII磷酸化，在转染细胞中可被PKA磷酸化。二维磷酸肽分析表明，丝氨酸842是GluR4上的主要磷酸化位点。此外，我们确定苏氨酸830是一个潜在的PKC磷酸化位点。这些结果表明，作为脱敏速度最快的AMPA受体亚基，GluR4可能受到磷酸化的调节。
