Kondoh K, Sano A, Kakimoto Y, Matsuda S, Sakanaka M
Department of Neuropsychiatry, Ehime University School of Medicine, Japan.
J Comp Neurol. 1993 Aug 22;334(4):590-602. doi: 10.1002/cne.903340407.
Prosaposin is the precursor for saposins A, B, C, and D, which are small lysosomal proteins required for the hydrolysis of sphingolipids by specific lysosomal hydrolases. With a monospecific anti-saposin C antibody, which cross-reacts with prosaposin but not with saposin A, B, or D, the present immunoblot experiments showed that the rat brain expresses an unprocessed approximately 72 kDa protein (possibly prosaposin) and little saposin C. Regional analysis demonstrated that prosaposin is abundant in the brainstem, hypothalamus, cerebellum, striatum, and hippocampus, and less abundant in the cerebral cortex. Consistent with this finding, prosaposin-like immunoreactive neurons and fibers as revealed by immunohistochemistry were observed frequently in subcortical regions. The medial septum, diagonal bands, basal nucleus of Meynert, ventral striatum, medial habenular nucleus, and motor nuclei of cranial nerve had significant numbers of immunoreactive neurons. There were also nerve fibers with prosaposin-like immunoreactivity in several projection fields of the above nuclei. Other brain areas that contained prosaposin-like immunoreactive neurons and/or processes were: several brain nuclei (nucleus caudate putamen, globus pallidus, substantia nigra, red nucleus) constituting the so-called extrapyramidal system, reticular thalamic nucleus, entopeduncular nucleus, mammillary nuclei, auditory relay nuclei, cerebellum, sensory cranial nerve nuclei, and the reticular formation. The distribution pattern of prosaposin is apparently different from that of other neuroactive substances so far examined, and thus prosaposin may be involved in novel central events.
鞘脂激活蛋白原是鞘脂激活蛋白A、B、C和D的前体，鞘脂激活蛋白A、B、C和D是特定溶酶体水解酶水解鞘脂所需的小溶酶体蛋白。使用一种单特异性抗鞘脂激活蛋白C抗体（该抗体与鞘脂激活蛋白原发生交叉反应，但不与鞘脂激活蛋白A、B或D发生交叉反应），目前的免疫印迹实验表明，大鼠脑表达一种未加工的约72 kDa蛋白（可能是鞘脂激活蛋白原），而鞘脂激活蛋白C含量很少。区域分析表明，鞘脂激活蛋白原在脑干、下丘脑、小脑、纹状体和海马中含量丰富，而在大脑皮层中含量较少。与这一发现一致，免疫组织化学显示的鞘脂激活蛋白原样免疫反应性神经元和纤维在皮层下区域频繁可见。内侧隔核、斜角带、迈内特基底核、腹侧纹状体、内侧缰核和脑神经运动核中有大量免疫反应性神经元。在上述核的几个投射区域中也有具有鞘脂激活蛋白原样免疫反应性的神经纤维。其他含有鞘脂激活蛋白原样免疫反应性神经元和/或突起的脑区包括：构成所谓锥体外系的几个脑核（尾状壳核、苍白球、黑质、红核）、丘脑网状核、内囊核、乳头体核、听觉中继核、小脑、感觉脑神经核和网状结构。鞘脂激活蛋白原的分布模式显然与目前检测的其他神经活性物质不同，因此鞘脂激活蛋白原可能参与了新的中枢事件。
