A new paradigm for Prelamin A proteolytic processing by ZMPSTE24: the upstream SY^LL cleavage occurs first and there is no CaaX processing by ZMPSTE24
A new paradigm for Prelamin A proteolytic processing by ZMPSTE24: the upstream SY^LL cleavage occurs first and there is no CaaX processing by ZMPSTE24
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ZMPSTE24 进行 Prelamin A 蛋白水解加工的新范例：首先发生上游 SY^LL 切割，并且 ZMPSTE24 不进行 CaaX 加工
DOI：
10.1101/2020.05.13.093849
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Nie L
中科院分区：
文献类型：
--
作者：
Nie L
人类ZMPSTE24是一种完整的膜锌金属蛋白酶，是将前层蛋白A转化为成熟层蛋白A所必需的，成熟层蛋白A是核层的一个组成部分，这种加工的失败会导致早衰疾病。ZMPSTE24也与2型糖尿病和病毒-宿主反应机制有关，但迄今为止，它唯一确认的底物是层状蛋白A的前体，层状蛋白A被认为经历了四种c端翻译后修饰，顺序如下：法尼化、SIM三肽切割、羧甲基化和上游“SY^LL”切割。在这里，我们提出的证据表明，事件的顺序不遵循公认的教条。我们用纯化的人ZMPSTE24结合FRET和质谱检测产物来评估人prelamin A长序列肽的切割。令人惊讶的是，我们发现“SY^LL”切割发生在c端CSIM修饰之前并且独立于CSIM修饰。我们还发现ZMPSTE24并没有进行预测的C^SIM三肽切割，而是去除了一个IM二肽。ZMPSTE24可以用典型的CaaX盒（C：半胱氨酸；a：脂肪族；X：任何残基）进行三肽切割，但前纤层蛋白a的C端不是真正的CaaX序列。无论前纤层蛋白A的c端修饰如何，ZMPSTE24都可以进行上游SY^LL切割，从而去除不需要的法酰化c端。因此，SY^LL切割失败，而不是c端加工，可能是导致类早衰疾病的原因。
Human ZMPSTE24, an integral membrane zinc metalloprotease, is required for conversion of prelamin A to mature lamin A, a component of the nuclear lamina and failure of this processing causes premature ageing disorders. ZMPSTE24 has also been implicated in both type 2 diabetes mellitus and in viral-host response mechanisms, but to date its only confirmed substrate is the precursor for lamin A. Prelamin A is thought to undergo four C-terminal post-translational modifications in the following order: farnesylation, SIM tripeptide cleavage, carboxymethylation and upstream “SY^LL” cleavage. Here we present evidence that the sequence of events does not follow the accepted dogma. We assessed cleavage of long human prelamin A sequence peptides by purified human ZMPSTE24 combined with FRET and mass spectrometry to detect products. Surprisingly, we found that the “SY^LL” cleavage occurs before and independent of the C-terminal CSIM modifications. We also found that ZMPSTE24 does not perform the predicted C^SIM tripeptide cleavage, but rather it removes an IM dipeptide. ZMPSTE24 can perform a tripeptide cleavage with a canonical CaaX box (C: cysteine; a: aliphatic; X: any residue), but the C-terminus of prelamin A is not a true CaaX sequence. Regardless of the C-terminal modifications of prelamin A, ZMPSTE24 can perform upstream SY^LL cleavage, thus removing the unwanted farnesylated C-terminus. Therefore, it is failure of SY^LL cleavage, not the C-terminal processing that is the likely cause of progeroid disorders.