Enzymatic cleavage of myoferlin releases a dual C2-domain module linked to ERK signalling.
Enzymatic cleavage of myoferlin releases a dual C2-domain module linked to ERK signalling.
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肌膜的酶促切割释放了与ERK信号链接的双C2域模块。
DOI：
10.1016/j.cellsig.2017.02.009
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发表时间：
2017-05
影响因子：
4.8
通讯作者：
Cooper ST
中科院分区：
文献类型：
--
作者：
Piper AK;Ross SE;Redpath GM;Lemckert FA;Woolger N;Bournazos A;Greer PA;Sutton RB;Cooper ST
Myoferlin 和 Dysferlin 是 Ca2+ 调节的囊泡融合蛋白 ferlin 家族密切相关的成员。 Dysferlin 被认为在膜修复过程中 Ca2+ 触发的囊泡融合中发挥作用。肌铁蛋白调节内吞作用、生长因子受体和粘附蛋白的再循环，并与癌细胞的转移潜力有关。我们之前的研究表明，dysferlin 在膜损伤过程中被钙蛋白酶切割，切割基序由交替剪接的外显子 40a 编码。在此，我们描述了肌成纤维蛋白的裂解，产生膜相关的双 C2 结构域“迷你肌成纤维蛋白”。肌铁蛋白具有两个酶切位点：一个由 C2DE 域内的外显子 38 编码的规范切割位点；接头中与 C2DE 相邻的第二个切割位点，由交替剪接的外显子 38a 编码，与 Dysferlin 外显子 40a 同源。当将两个肌铁蛋白裂解位点引入 Dysferlin 时，可以在功能上替代外显子 40a，以响应膜损伤而赋予 Ca2+ 触发的钙蛋白酶裂解。然而，肌成纤维蛋白的酶促裂解是复杂的，在不同的细胞系中显示出组成型或Ca2+增强型裂解，这不仅仅依赖于钙蛋白酶-1或-2。通过信号蛋白磷酸蛋白阵列探索了肌成纤维蛋白裂解的功能影响，揭示了可裂解肌成纤维蛋白（而非不可裂解亚型）的异位表达对 ERK1/2 的特异性激活。总之，我们从分子上定义了肌成纤维蛋白内的两个酶裂解位点，并证明可以在人类乳腺癌肿瘤样本和细胞系中检测到“微型肌成纤维蛋白”。这些数据进一步说明，ferlin 的酶促裂解是一种进化保留的机制，用于释放功能专门的微型模块。
Myoferlin and dysferlin are closely related members of the ferlin family of Ca2+-regulated vesicle fusion proteins. Dysferlin is proposed to play a role in Ca2+-triggered vesicle fusion during membrane repair. Myoferlin regulates endocytosis, recycling of growth factor receptors and adhesion proteins, and is linked to the metastatic potential of cancer cells. Our previous studies establish that dysferlin is cleaved by calpains during membrane injury, with the cleavage motif encoded by alternately-spliced exon 40a. Herein we describe the cleavage of myoferlin, yielding a membrane-associated dual C2 domain ‘mini-myoferlin’. Myoferlin bears two enzymatic cleavage sites: a canonical cleavage site encoded by exon 38 within the C2DE domain; and a second cleavage site in the linker adjacent to C2DE, encoded by alternately-spliced exon 38a, homologous to dysferlin exon 40a. Both myoferlin cleavage sites, when introduced into dysferlin, can functionally substitute for exon 40a to confer Ca2+-triggered calpain cleavage in response to membrane injury. However, enzymatic cleavage of myoferlin is complex, showing both constitutive or Ca2+-enhanced cleavage in different cell lines, that is not solely dependent on calpains-1 or -2. The functional impact of myoferlin cleavage was explored through signalling protein phospho-protein arrays revealing specific activation of ERK1/2 by ectopic expression of cleavable myoferlin, but not an uncleavable isoform. In summary, we molecularly define two enzymatic cleavage sites within myoferlin and demonstrate ‘mini-myoferlin’ can be detected in human breast cancer tumour samples and cell lines. These data further illustrate that enzymatic cleavage of ferlins is an evolutionarily preserved mechanism to release functionally specialized mini-modules.
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