Simonson L, Baudry M, Siman R, Lynch G
Brain Res. 1985 Feb 18;327(1-2):153-9. doi: 10.1016/0006-8993(85)91509-4.
Calcium dependent proteolytic activity in the soluble fraction of various rat brain regions was assayed using 14C-radiolabelled denatured casein as a substrate. Two forms of activity, distinguishable by their calcium requirement for half maximal activation (5 and 80 microM), were found; both were blocked by sulfhydryl alkylating agents and thiol proteinase inhibitors. Preincubation at 58 degrees C for 10 min also eliminated the high threshold activity. These characteristics are identical to those reported for calcium activated neutral proteinases ('calpains') found in other tissues. Calpain activity varied markedly across brain regions. The greatest values for the high threshold enzyme were found in pons-medulla followed by cerebellum/mesencephalon and finally the telencephalon. The low threshold enzyme had low levels of activity throughout the brainstem and diencephalon and was barely detectable in telencephalic structures. In contrast, a previously described endogenous inhibitor of calpain, 'calpastatin', was found not to vary in its activity across brain regions. Calpain activity was high in the prenatal brain, but while the hindbrain maintained high levels of activity into adulthood, the activity in the forebrain dropped 80% during the early postnatal period. The differences between forebrain and hindbrain activity levels were evident during the first 5 days of the neonatal period, suggesting that glial cell differentiation is not responsible for the regional variations found in the adult. These results are discussed with regard to the possibility that the turnover of anatomical structures differs between brain regions.
以14C放射性标记的变性酪蛋白为底物，检测了不同大鼠脑区可溶部分的钙依赖性蛋白水解活性。发现了两种活性形式，通过它们对半数最大激活所需钙浓度（5和80微摩尔）的不同可区分；二者均被巯基烷基化剂和巯基蛋白酶抑制剂所阻断。在58℃预孵育10分钟也消除了高阈值活性。这些特征与在其他组织中发现的钙激活中性蛋白酶（“钙蛋白酶”）的特征相同。钙蛋白酶活性在不同脑区有显著差异。高阈值酶活性最高的是脑桥-延髓，其次是小脑/中脑，最后是端脑。低阈值酶在整个脑干和间脑活性水平较低，在端脑结构中几乎检测不到。相反，先前描述的钙蛋白酶内源性抑制剂“钙蛋白酶抑制蛋白”，其活性在不同脑区并无差异。钙蛋白酶活性在产前脑中较高，但虽然后脑在成年期仍保持较高活性水平，但前脑的活性在出生后早期下降了80%。新生期的头5天，前脑和后脑活性水平的差异就很明显，这表明神经胶质细胞分化并非导致成体中发现的区域差异的原因。本文就脑区之间解剖结构更新可能存在差异这一可能性对这些结果进行了讨论。
