Matsuura Tomokazu, Harrison Rachael A, Westwell Andrew D, Nakamura Hajime, Martynyuk Anatoly E, Sumners Colin
Dept. of Physiology and Functional Genomics, College of Medicine, University of Florida, Box 100274, 1600 SW Archer Rd., Gainesville, FL 32610-0274, USA.
Am J Physiol Cell Physiol. 2007 Jul;293(1):C211-7. doi: 10.1152/ajpcell.00615.2006. Epub 2007 Mar 14.
In previous studies, we determined that macrophage migration inhibitory factor (MIF), acting intracellularly via its intrinsic thiol-protein oxidoreductase (TPOR) activity, stimulates basal neuronal delayed-rectifier K(+) current (I(Kv)) and inhibits basal and angiotensin (ANG) II-induced increases in neuronal activity. These findings are the basis for our hypothesis that MIF is a negative regulator of ANG II actions in neurons. MIF has recently been recategorized as a member of the thioredoxin (Trx) superfamily of small proteins. In the present study we have examined whether Trx influences basal and ANG II-modulated I(Kv) in an effort to determine whether the Trx superfamily can exert a general regulatory influence over neuronal activity and the actions of ANG II. Intracellular application of Trx (0.8-80 nM) into rat hypothalamic/brain stem neurons in culture increased neuronal I(Kv), as measured by voltage-clamp recordings. This effect of Trx was abolished in the presence of the TPOR inhibitor PMX 464 (800 nM). Furthermore, the mutant protein recombinant human C32S/C35S-Trx, which lacks TPOR activity, failed to alter neuronal I(Kv). Trx applied at a concentration (0.08 nM) that does not alter basal I(Kv) abolished the inhibition of neuronal I(Kv) produced by ANG II (100 nM). Given our observation that ANG II increases Trx levels in neuronal cultures, it is possible that Trx (like MIF) has a negative regulatory role over basal and ANG II-stimulated neuronal activity via modulation of I(Kv). Moreover, these data suggest that TPOR may be a general mechanism for negatively regulating neuronal activity.
在先前的研究中，我们确定巨噬细胞移动抑制因子（MIF）通过其内在的硫醇 - 蛋白质氧化还原酶（TPOR）活性在细胞内发挥作用，刺激基础神经元延迟整流钾电流（I(Kv)），并抑制基础及血管紧张素（ANG）II诱导的神经元活动增加。这些发现是我们提出的MIF是神经元中ANG II作用的负调节因子这一假说的基础。MIF最近被重新归类为小蛋白硫氧还蛋白（Trx）超家族的成员。在本研究中，我们研究了Trx是否影响基础及ANG II调节的I(Kv)，以确定Trx超家族是否能对神经元活动及ANG II的作用发挥普遍的调节影响。通过电压钳记录测量，将Trx（0.8 - 80 nM）细胞内应用于培养的大鼠下丘脑/脑干神经元可增加神经元I(Kv)。在存在TPOR抑制剂PMX 464（800 nM）的情况下，Trx的这种作用被消除。此外，缺乏TPOR活性的突变蛋白重组人C32S/C35S - Trx未能改变神经元I(Kv)。以不改变基础I(Kv)的浓度（0.08 nM）应用Trx可消除ANG II（100 nM）对神经元I(Kv)的抑制作用。鉴于我们观察到ANG II可增加神经元培养物中Trx的水平，Trx（如MIF）有可能通过调节I(Kv)对基础及ANG II刺激的神经元活动发挥负调节作用。此外，这些数据表明TPOR可能是负调节神经元活动的一种普遍机制。
