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Myelin Oligodendrocyte Glycoprotein Peptide (35-55), mouse, rat 是中枢神经鞘的一个次要成分。Myelin Oligodendrocyte Glycoprotein Peptide (35-55), mouse, rat引发复发缓解性神经系统疾病，伴有广泛的斑块样脱髓鞘。还能诱导强效的 T细胞和 B 细胞反应，同时是高度脑源性的。
Myelin Oligodendrocyte Glycoprotein Peptide (35-55), mouse, rat is a minor component of CNS myelin. Myelin Oligodendrocyte Glycoprotein Peptide (35-55), mouse, rat produces a relapsing-remitting neurological disease with extensive plaque-like demyelination. Myelin Oligodendrocyte Glycoprotein Peptide (35-55), mouse, rat induces strong T and B cell responses and is highly encephalitogenic[1][2][3].

 Caspase酶对应的底物，Caspases（半胱氨酸天冬氨酸蛋白酶，半胱氨酸依赖性天冬氨酸定向蛋白酶）是一类蛋白酶家族，其功能与凋亡（程序性细胞死亡），坏死和发烧（炎症）的过程密切相关。

       什么是胱天蛋白酶？

      胱天蛋白酶（Caspases）是含半胱氨酸的天冬氨酸蛋白水解酶，它们是为细胞凋亡的主要介质。多种受体，例如TNF-α 受体，FasL受体，TLR和死亡受体，以及Bcl-2和凋亡抑制剂（IAP）蛋白家族参与并调节该caspase依赖性凋亡途径。一旦Caspase受到上游信号（外部或内在）刺激被激活，即会参与执行下游蛋白底物的水解作用，并触发一系列事件，导致细胞分解，死亡，吞噬作用和细胞碎片的清除。

      人Caspases酶

      人的Caspases家族基于序列相似性和生物学功能等共性主要可分为三大类：第一类由具有长胱天蛋白酶募集结构域的“炎症”胱天蛋白酶组成，他们对P4位上的较大的芳香族或疏水性残基具有亲和力。第二类由具有短的前体结构域的“细胞凋亡效应”胱天蛋白酶组成，而第三类由具有长的前提结构域的Pap位置具有亮氨酸或缬氨酸底物亲和力的“凋亡引发剂”胱天蛋白酶组成（表1）。

       表1. 人胱天蛋白酶的功能分类：

       启动器Caspase和效应器Caspase酶

      根据其在凋亡胱天蛋白酶途径中的作用，胱天蛋白酶可分为两类：启动器和效应器Caspase酶。启动器和效应器Caspas酶都具有由小亚基和大亚基组成的催化位点，Caspase酶的识别位

      凋亡启动器Caspase酶，例如caspase-2，-8，-9和-10可以启动caspase激活级联反应。Caspase-8对于形成死亡诱导信号复合物（DISC）是必不可少的，并且在激活后，Caspase-8激活下游效应子Caspase（例如Caspase 3）并介导线粒体中细胞色素c的释放。Caspase-8已被证明对IETD肽序列具有相对较高的底物选择性。凋亡效应胱天蛋白酶例如Caspase-3，-6和-7虽然不负责启动级联途径，但是当被激活时，它们在级联的中间和后续步骤中起着不可或缺的作用。Caspase-3（CPP32 / apopain）是关键效应器，因为它放大了来自启动器Caspase的信号，使用对Caspase-3有选择性的DEVD肽序列对活化的Caspase-3进行检测，可以检测Caspase-3的活性。

       Caspase酶底物和抑制剂

      Caspase底物和抑制剂由两个关键成分组成：Caspase识别序列和信号产生或蛋白酶抑制基序。不同Caspase识别序列不同，一般由三个或四个氨基酸组成（表2）。Caspase酶识别序列的N端通常有乙酰基（Ac）或碳苯甲氧基（Z）基团修饰，以增强膜的通透性。对应的Caspase识别特定的肽序列为其酶促反应切割位点，释放产生信号或抑制信号的基序。Caspase的显色和荧光底物均以相似的方式起作用，其中底物的信号或颜色强度与蛋白水解活性成正比。

       表2. Caspase的底物及其序列

         Caspase酶的显色底物

      Caspase的显色底物是有Caspase识别序列及生色基团组成，常见的生色团有pNA（对硝基苯胺或4-硝基苯胺），可使用酶标仪或分光光度计在405 nm处进行光密度检测。

       表3. Caspase的显色底物

       Caspase的荧光底物

      Caspase的荧光底物的结构包含与半胱天冬酶识别相关的荧光团，例如7-氨基-4-甲基香豆素（AMC），7-氨基-4-三氟甲基香豆素（AFC）， Rhodamine 110（R110）或ProRed™620。R110的Caspase底物比基于香豆素的Caspase底物（例如AMC和AFC）更敏感，但由于两步裂解过程，其动态范围更窄。 建议将R110标记的Caspase底物用于终点法测定，而将AMC和AFC标记的 Caspase底物用于动力学测定。

      图.从左到右，分别是AMC（7-氨基-4-甲基香豆素），AFC（7-氨基-4-三氟甲基香豆素），Rhodamine 110（R110）和ProRed™620的激发和发射光谱。

       表4.荧光半胱天冬酶底物。

       注意：

        1.ε=在其最大吸收波长处的摩尔消光系数（单位= cm ^-1M ^-1）。

      2.Φ=水性缓冲液（pH 7.2）中的荧光量子产率。

       Caspase抑制剂

      Caspase抑制剂能与Caspase的活性位点结合并形成可逆或不可逆的连接，通常，Caspase抑制剂的结构由Caspase识别序列，诸如醛（-CHO）或氟甲基酮（-FMK）的官能团组成。具有醛官能团的胱天蛋白酶抑制剂是可逆的，而具有FMK的抑制剂是不可逆的。半胱天冬酶底物和抑制剂都具有较小的细胞毒性作用，因此，它们是研究半胱天冬酶活性的有用工具。

       表5. 可逆和不可逆的Caspase酶抑制剂

Experimental Allergic Encephalomyelitis (EAE) Peptides are active fragment of the myelin basic protein. By a cellmediated immune response, the peptide causes experimental allergic encephalomyelitis, which is an inflammatory demyelinating disease of the central nervous system. These peptides have been used as a model for studying multiple sclerosis (MS) due to the clinical and histopathological similarities of the inflammatory diseases affecting the central nervous system. Both Myelin PLP (PLP-3602-PI) and MOG (PMG-3660-PI) are antigenic peptides that induce EAE by binding to MHCII molecules on antigen presenting cells where they are recognized by class-II restricted T cells.

Discovery
Westall et al., in 1971 identified a peptide that causes experimental allergic encephalomyelitis 1,2. EAE is an autoimmune disease inducible by encephalitogenic helper T cells expressing Vβ8. Owhashi M et al., in 1997 examined the relationship between the stressor-induced alternation of clinical EAE and the induction of autoreactive T cells using Lewis rats 3.

Structural Characteristics
Belogurov AA et al demonstrated that autoantibodies (AAb) in multiple sclerosis (MS) reveal site-specific binding and cleavage toward myelin basic protein (MBP) epitope library. They have found several fragments of MBP immunodominant in terms of AAb binding and applied these peptides to DA rats with induced protracted relapsing EAE most closely related to MS. DA rats with EAE induced by syngenic spinal cord homogenate in complete Freund's adjuvant were treated by nasal route with human MBP 46–62, 81–102, 124–139, 147–170, and Copaxone®. MBP 124–139 and 147–170 displayed only mild therapeutic effects but MBP 46–62 significantly reduced EAE, reflected by lower clinical scores and shorter EAE duration compared to controls 4.  Three peptides overlapping the tryptophan region of bovine CNS myelin basic protein were synthesized by the solid phase procedure of Merrifield. These were the nonapeptide H-Phe-Ser-Trp-Gly-Ala-Glu-Gly-Gln-Lys-OH, the octapeptide H-Ser-Trp-Gly-Ala-Glu-Gly-Gln-Lys-OH, and the heptapeptide H-Trp-Gly-Ala-Glu-Gly-Gln-Lys-OH. They were tested fro encephalitogenic activity in guinea pigs with either Freund's complete adjuvant containing M. tuberculosis or muramyl dipeptide in incomplete Freud's adjuvant at doses of 10 µg per animal. The results show that deletion of one or two residues from the amino-terminal end of the nonapeptide destroyed the ability of the shorter peptides to induce clinical but not histological signs of EAE 5. 

Mode of Action
Proteolipid protein (PLP) is the major protein of central nervous system (CNS) myelin. SJL(H-2S) mice immunized with a synthetic peptide corresponding to PLP residues 139-151 (HSLGKWLGHPDKF) develop acute EAE. A T cell line and 4 clones were derived from SJL/J mice were immunizied with this synthetic peptide. Severe clinical and histological EAE was induced by adoptive transfer of the peptide-specific T cell line and 3 of 4 T cell clones. The T cell line/clones all responded strongly to PLP peptide 139-151 in in vitro proliferative assays. However, two different reactivity patterns emerged when truncated PLP peptides 141-150 and 141-149 were tested, suggesting that more than 1 epitope may be present within the PLP 139-151 determinant. Two truncated PLP peptides were compared for the ability to induce EAE in vivo and proliferative responses in vitro. Immunization with PLP peptide 141-150 induced acute EAE in about 70% of mice tested, but PLP peptide 141-149 induced a comparatively mild form of EAE in 4 out of 9 mice tested. Lymph node cells from mice immunized with these peptides showed in vitro proliferative responses to each of the peptides, but the response to peptide 139-151 was always strongest. These combined in vivo and in vitro data further define the epitopes involved in PLP-induced EAE in SJL mice. Furthermore, the availability of multiple PLP-specific T cell clones will enable to study the diversity of the T cell repertoire to PLP 6.

Functions
Cell mediated autoimmune response, EAE is a cell mediated autoimmune response directed against autologous central nervous system myelin 7.
Sensitization with myelin basic protein (MBP), a major protein constituent of central nervous system compact myelin, emulsified in complete Freund's adjuvant, produce the full clinical and histological picture of EAE in a wide variety of animal.
The encephalitogenic determinants responsible for EAE induction are species-specific. That is, different sequences of amino acid residues located at unique positions within the MBP molecule are critical for the induction of EAE in each mammalian species 8.
Stressor-induced suppression of clinical EAE is not simply because of the failure of induction of autoreactive T cells, nor localization of the autoreactive T cells in the central nervous system 3.
Species-specific immune response, the capacity of MBP in complete Freund's adjuvant to induce an encephalitogenic immune response against autologous central nervous system myelin in a given mammalian species appears to be dictated by latent, species-specific immune response genes which presumably encode antigen-receptor molecules recognizing specific MBP sequences 1.

References

Westall FC, Robinson AB, Caccam J, Jackson J, Ylar EH, (1971). Essential chemical requirements for induction of allergic encephalomyelitis. Nature, 229(5279):22-24.
Shapira R, Chou FC, McKneally S, Urban E, Kibler RF (1971). Biologicl activity and synthesis of an encephalitogenic determinant. Science, 173(998):736-738.
Owhashi M, Shouzui Y, Arita H (1997). Stress down-regulates experimental allergic encephalomyelitis (EAE) but permits activation and localization of autoreactive vβ8.2+ T Cells.  International Journal of Neuroscience, 89(3-4):177-188.
Belogurov AA Jr, Zargarova TA, Turobov VI, Novikova NI, Favorova OO, Ponomarenko NA, Gabibov AG  (2009). Suppression of ongoing experimental allergic encephalomyelitis in DA rats by novel peptide drug, structural part of human myelin basic protein 46–62.   Autoimmunity, 42(4):362-364.
Levit S, Powers JM, Milek D, Brostoff SW (1980). Peptide length requirement for experimental allergic encephalomyelitis in guinea pigs. Neurochem Res., 5(1):37-42.
 Kuchroo VK, Sobel RA, Yamamura T, Greenfield E, Dorf ME, Lees MB (1991). Induction of Experimental Allergic Encephalomyelitis by Myelin Proteolipid-Protein-Specific T Cell Clones and Synthetic Peptides. Pathobiology, 59(5):305-312.
Paterson PY (1982). Molecular and cellular determinants of neuroimmunologic inflammatory disease. Fed. Proc. Fed. Am. Soc. Exp. Biol., 41:2569-2576.
Hashim GA (1978). Myelin basic protein: structure, function and antigenic determinants. Immunol. Rev., 39:60-107.