Vincent B, Beaudet A, Dauch P, Vincent J P, Checler F
Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UPR 411, Valbonne, France.
J Neurosci. 1996 Aug 15;16(16):5049-59. doi: 10.1523/JNEUROSCI.16-16-05049.1996.
Endopeptidase 3.4.24.16 belongs to the zinc-containing metalloprotease family and likely participates in the physiological inactivation of neurotensin. The peptidase displays distinct features in pure primary cultured neurons and astrocytes. Neuronal maturation leads to a decrease in the proportion of endopeptidase 3.4.24.16-bearing neurons and to a concomitant increase in endopeptidase 3.4.24.16 activity and mRNA content. By contrast, there is no change with time in endopeptidase 3.4.24.16 activity or content in astrocytes. Primary cultured neurons exhibit both soluble and membrane-associated endopeptidase 3.4.24.16 activity. The latter behaves as an ectopeptidase on intact plated neurons and resists treatments with 0.2% digitonin and Na2CO3. Further evidence for an association of the enzyme with plasma membranes was provided by cryoprotection experiments and electron microscopic analysis. The membrane-associated form of endopeptidase 3.4.24.16 increased during neuronal differentiation and appears to be mainly responsible for the overall augmentation of endopeptidase 3.4.24.16 activity observed during neuronal maturation. Unlike neurons, astrocytes only contain soluble endopeptidase 3.4.24.16. Astrocytes secrete the enzyme through monensin, brefeldin A, and forskolin-independent mechanisms. This indicates that endopeptidase 3.4.24.16 is not released by classical regulated or constitutive secreting processes. However, secretion is blocked at 4 degrees C and by 8 bromo cAMP and is enhanced at 42 degrees C, two properties reminiscent of that of other secreted proteins lacking a classical signal peptide. By contrast, neurons appear unable to secrete endopeptidase 3.4.24.16.
内肽酶3.4.24.16属于含锌金属蛋白酶家族，可能参与神经降压素的生理失活过程。该肽酶在原代纯培养的神经元和星形胶质细胞中表现出不同的特性。神经元成熟导致含内肽酶3.4.24.16的神经元比例下降，同时内肽酶3.4.24.16的活性和mRNA含量增加。相比之下，星形胶质细胞中内肽酶3.4.24.16的活性或含量不会随时间发生变化。原代培养的神经元同时表现出可溶性和膜相关的内肽酶3.4.24.16活性。后者在完整的贴壁神经元上表现为外肽酶，并且能抵抗0.2%洋地黄皂苷和碳酸钠的处理。冷冻保护实验和电子显微镜分析为该酶与质膜的关联提供了进一步的证据。内肽酶3.4.24.16的膜相关形式在神经元分化过程中增加，似乎是神经元成熟过程中观察到的内肽酶3.4.24.16活性总体增加的主要原因。与神经元不同，星形胶质细胞仅含有可溶性内肽酶3.4.24.16。星形胶质细胞通过莫能菌素、布雷菲德菌素A和不依赖福斯高林的机制分泌该酶。这表明内肽酶3.4.24.16不是通过经典的调节性或组成性分泌过程释放的。然而，分泌在4℃和8-溴环磷酸腺苷作用下被阻断，而在42℃时增强，这两个特性让人联想到其他缺乏经典信号肽的分泌蛋白。相比之下，神经元似乎无法分泌内肽酶3.4.24.16。
