Colledge M, Froehner S C
Department of Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
J Neurosci. 1997 Jul 1;17(13):5038-45. doi: 10.1523/JNEUROSCI.17-13-05038.1997.
Tyrosine phosphorylation of the nicotinic acetylcholine receptor (AChR) is associated with an altered rate of receptor desensitization and also may play a role in agrin-induced receptor clustering. We have demonstrated a previously unsuspected interaction between Torpedo AChR and the adaptor protein Grb2. The binding is mediated by the Src homology 2 (SH2) domain of Grb2 and the tyrosine-phosphorylated delta subunit of the AChR. Dephosphorylation of the delta subunit abolishes Grb2 binding. A cytoplasmic domain of the delta subunit contains a binding motif (pYXNX) for the SH2 domain of Grb2. Indeed, a phosphopeptide corresponding to this region of the delta subunit binds to Grb2 SH2 fusion proteins with relatively high affinity, whereas a peptide lacking phosphorylation on tyrosine exhibits no binding. Grb2 is colocalized with the AChR on the innervated face of Torpedo electrocytes. Furthermore, Grb2 specifically copurifies with AChR solubilized from postsynaptic membranes. These data suggest a novel role for tyrosine phosphorylation of the AChR in the initiation of a Grb2-mediated signaling cascade at the postsynaptic membrane.
烟碱型乙酰胆碱受体（AChR）的酪氨酸磷酸化与受体脱敏速率的改变有关，并且可能在集聚蛋白诱导的受体聚集过程中发挥作用。我们已经证明了电鳐AChR与衔接蛋白Grb2之间存在此前未被怀疑的相互作用。这种结合是由Grb2的Src同源2（SH2）结构域和AChR的酪氨酸磷酸化δ亚基介导的。δ亚基的去磷酸化会消除Grb2的结合。δ亚基的一个胞质结构域包含一个针对Grb2的SH2结构域的结合基序（pYXNX）。实际上，对应于δ亚基这一区域的磷酸化肽段以相对较高的亲和力与Grb2 SH2融合蛋白结合，而酪氨酸未磷酸化的肽段则不表现出结合。Grb2与电鳐肌细胞受神经支配面上的AChR共定位。此外，Grb2与从突触后膜溶解的AChR特异性共纯化。这些数据表明AChR的酪氨酸磷酸化在突触后膜启动Grb2介导的信号级联反应中具有新的作用。
