Vazquez M E, Ebendal T
Department of Developmental Biology, Uppsala University, Sweden.
Neuroreport. 1991 Oct;2(10):593-6. doi: 10.1097/00001756-199110000-00010.
Nerve growth factor (NGF) acts by binding to specific sets of neurons. Low-affinity binding (Kd of 10(-9) M) is mediated via a 75 kDa glycoprotein (LNGFR). Recently, a 140 kDa tyrosine protein kinase encoded by the proto-oncogene trk has been found to bind NGF with high affinity (Kd of 10(-11) M) and to evoke neurotrophic responses. In addition, the related trkB protein and the LNGFR have been shown to bind brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) with an affinity of Kd 10(-9) M. We demonstrate the distribution of mRNA encoding the neurotrophin-binding proteins in the forebrain of the 21-day-old Sprague-Dawley rat by in-situ hybridization. Expression of trk and LNGFR mRNA showed co-localization and was restricted to the medial septal nucleus and the nucleus of Broca's diagonal band, suggesting a receptor function in these cells for both proteins encoded. In contrast, expression of trkB was widely spread in many areas. Thus trkB protein might serve general functions in the forebrain.
神经生长因子（NGF）通过与特定的神经元群体结合而发挥作用。低亲和力结合（解离常数Kd为10^(-9) M）是通过一种75 kDa的糖蛋白（LNGFR）介导的。最近发现，由原癌基因trk编码的一种140 kDa的酪氨酸蛋白激酶能以高亲和力（解离常数Kd为10^(-11) M）结合NGF并引发神经营养反应。此外，相关的trkB蛋白和LNGFR已被证明能以解离常数Kd为10^(-9) M的亲和力结合脑源性神经营养因子（BDNF）和神经营养素-3（NT-3）。我们通过原位杂交展示了21日龄斯普拉格-道利大鼠前脑中编码神经营养因子结合蛋白的mRNA的分布。trk和LNGFR mRNA的表达显示出共定位，且局限于内侧隔核和布罗卡斜角带核，这表明这两种编码蛋白在这些细胞中具有受体功能。相比之下，trkB的表达广泛分布于许多区域。因此，trkB蛋白可能在前脑中发挥一般性功能。
