Hinko A, Pearlmutter A F
J Neurosci Res. 1987;17(1):71-9. doi: 10.1002/jnr.490170111.
Our laboratory has reported previously the characteristics of specific AVP binding to rat hippocampal synaptic membranes (SPM) in the presence of Ni2+ [Costantini MG, Pearlmutter AF: J Biol Chem 259: 11739-11745, 1984]. We extended our investigation to determine the effects of Ni2+, (AVP), and AVP analogs on SPM protein phosphorylation. Ni2+ (5 mM) caused a dramatic reduction in phosphorylation of most SPM phosphoproteins. The most prominent protein which is phosphorylated in SPM has a molecular weight of 48 kilodaltons (KDa) and has been named B50 or F1; this protein shows altered phosphorylation in vitro in response to long-term potentiation in vivo as well as changes induced by exposure of SPM to ACTH (1-24), dopamine, and somatostatin. AVP and related peptides reduced phosphorylation of this pre-synaptic phosphoprotein in the following order of potency: AVP = oxytocin greater than DG-AVP greater than dDAVP greater than d(CH2)5Tyr(Me)AVP = [pGlu4,Cyt6]AVP-(4-9). Except for the pressor antagonist d(CH2)5Tyr(Me)AVP, this corresponds to their relative efficacy in displacing 3H-AVP from high-affinity specific binding sites on rat hippocampal synaptic membranes. Ni2+ did not alter the degree of inhibition caused by the peptides. When SPM were treated with AVP after the attainment of maximum 32P incorporation, AVP inhibited dephosphorylation over a 30-min period. Our results show that AVP can alter both phosphorylation and dephosphorylation of hippocampal SPM phosphoproteins in vitro; the direction of these effects depends upon experimental conditions. Since B50/F1 is known to be a substrate for protein kinase C, AVP may act by inhibition of protein kinase C activity, either directly or indirectly.
我们实验室之前报道过在Ni2+存在的情况下，特异性抗利尿激素（AVP）与大鼠海马突触膜（SPM）结合的特性[科斯坦蒂尼MG，珀尔马特AF：《生物化学杂志》259：11739 - 11745，1984]。我们扩展了研究，以确定Ni2+、（AVP）和AVP类似物对SPM蛋白磷酸化的影响。Ni2+（5 mM）导致大多数SPM磷蛋白的磷酸化显著降低。在SPM中被磷酸化的最突出蛋白质分子量为48千道尔顿（KDa），已被命名为B50或F1；该蛋白质在体外表现出因体内长期增强以及SPM暴露于促肾上腺皮质激素（1 - 24）、多巴胺和生长抑素所诱导的变化而发生的磷酸化改变。AVP及相关肽按以下效力顺序降低这种突触前磷蛋白的磷酸化：AVP = 催产素＞去甘氨酰胺精加压素（DG - AVP）＞去氨基精加压素（dDAVP）＞d（CH2）5Tyr（Me）AVP = [pGlu4，Cyt6]AVP - （4 - 9）。除了升压拮抗剂d（CH2）5Tyr（Me）AVP外，这与它们从大鼠海马突触膜上的高亲和力特异性结合位点置换3H - AVP的相对效力相对应。Ni2+并未改变肽所引起的抑制程度。当在达到最大32P掺入后用AVP处理SPM时，AVP在30分钟内抑制了去磷酸化。我们的结果表明，AVP在体外可改变海马SPM磷蛋白的磷酸化和去磷酸化；这些效应的方向取决于实验条件。由于已知B50/F1是蛋白激酶C的底物，AVP可能直接或间接通过抑制蛋白激酶C活性发挥作用。
