Lysosomal cathepsin D mediates endogenous mucin glycodomain catabolism in mammals.
Lysosomal cathepsin D mediates endogenous mucin glycodomain catabolism in mammals.
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DOI：
10.1073/pnas.2117105119
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发表时间：
2022-09-27
影响因子：
11.1
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中科院分区：
文献类型：
--
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粘蛋白是一种高度O-糖基化的蛋白质，存在于人体许多细胞的表面。为了分解粘蛋白糖域，细胞必须分解肽主链和附加的糖链。在哺乳动物中，这两个过程被认为在很大程度上是独立发生的。在这里，我们证明了人溶酶体酶组织蛋白酶D可以将完全糖化的粘蛋白结构域蛋白分解成糖肽，当组织蛋白酶D活性丧失时，粘蛋白在一些组织中积累。这些发现提示了哺乳动物内源性粘蛋白糖域分解代谢的途径，这与糖肽的主要组织相容性复合体的负载和肿瘤细胞外基质的降解有关，以及逆转病理性粘蛋白聚集的潜在治疗方法。粘蛋白在功能上与一系列人类病理有关，包括囊性纤维化、流感、细菌性心内膜炎、肠道生物失调和癌症。这些观察结果推动了粘蛋白生物合成的研究以及抑制粘蛋白糖基化的策略的发展。然而，哺乳动物分解粘蛋白的途径仍未得到充分研究。从对人类溶酶体储存障碍中N-糖蛋白的分析得出的典型观点是，糖的降解和蛋白分解是相继发生的。在这里，我们通过提供遗传和生化证据来挑战这一观点，该证据支持哺乳动物在没有事先脱糖基化的情况下对高度O-糖基化的粘蛋白结构域进行蛋白质分解。利用活性筛选和质谱法，我们将小鼠肝脏的粘蛋白降解活性归因于溶酶体组织蛋白酶D。用纯化的人肝脏溶酶体组织蛋白D消化底物的糖蛋白质组学为蛋白在高密度O-糖基化结构域内的降解提供了直接证据。最后，在人类溶酶体储存障碍的小鼠模型中，组织蛋白酶D的敲除导致了驻留在肝脏的巨噬细胞中粘蛋白的积累。我们的发现表明，粘蛋白降解活性是哺乳动物组织内源性糖蛋白分解代谢途径的一个组成部分。
Mucins are densely O-glycosylated proteins found on the surfaces of many cells in the human body. In order to break down mucin glycodomains, cells must catabolize both the peptide backbone and the appended glycans. In mammals, these two processes were thought to occur largely independently. Here, we show that the human lysosomal enzyme cathepsin D can proteolyze fully glycosylated mucin domains into glycopeptides and that mucins accumulate in some tissues when cathepsin D activity is lost. These findings suggest a mammalian pathway for endogenous mucin glycodomain catabolism, with implications for major histocompatibility complex loading of glycopeptides and tumor extracellular matrix degradation, as well as potential therapies to reverse pathological mucin accumulation. Mucins are functionally implicated in a range of human pathologies, including cystic fibrosis, influenza, bacterial endocarditis, gut dysbiosis, and cancer. These observations have motivated the study of mucin biosynthesis as well as the development of strategies for inhibition of mucin glycosylation. Mammalian pathways for mucin catabolism, however, have remained underexplored. The canonical view, derived from analysis of N-glycoproteins in human lysosomal storage disorders, is that glycan degradation and proteolysis occur sequentially. Here, we challenge this view by providing genetic and biochemical evidence supporting mammalian proteolysis of heavily O-glycosylated mucin domains without prior deglycosylation. Using activity screening coupled with mass spectrometry, we ascribed mucin-degrading activity in murine liver to the lysosomal protease cathepsin D. Glycoproteomics of substrates digested with purified human liver lysosomal cathepsin D provided direct evidence for proteolysis within densely O-glycosylated domains. Finally, knockout of cathepsin D in a murine model of the human lysosomal storage disorder neuronal ceroid lipofuscinosis 10 resulted in accumulation of mucins in liver-resident macrophages. Our findings imply that mucin-degrading activity is a component of endogenous pathways for glycoprotein catabolism in mammalian tissues.
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影响因子：
64.8
作者：
Laqtom NN;Dong W;Medoh UN;Cangelosi AL;Dharamdasani V;Chan SH;Kunchok T;Lewis CA;Heinze I;Tang R;Grimm C;Dang Do AN;Porter FD;Ori A;Sabatini DM;Abu-Remaileh M
通讯作者：
Abu-Remaileh M
影响因子：
10.1
作者：
Malaker SA;Penny SA;Steadman LG;Myers PT;Loke JC;Raghavan M;Bai DL;Shabanowitz J;Hunt DF;Cobbold M
通讯作者：
Cobbold M
影响因子：
13.3
作者：
Marques, Andre R. A.;Di Spiezio, Alessandro;Saftig, Paul
通讯作者：
Saftig, Paul
影响因子：
4.8
作者：
Aghdassi, Ali A.;John, Daniel S.;Lerch, Markus M.
通讯作者：
Lerch, Markus M.
影响因子：
6
作者：
Kim, YJ;Borsig, L;Varki, A
通讯作者：
Varki, A