Bulliard Manon, Pinjusic Katarina, Iacobucci Laura, Schmuziger Céline, Fournier Nadine, Constam Daniel B
École Polytechnique Fédérale de Lausanne (EPFL) SV ISREC, Station 19, 1015, Lausanne, Switzerland.
Dana-Farber Cancer Institute, 450 Brookline Avenue, Boston, MA, 02215, USA.
Nat Commun. 2025 Mar 10;16(1):2354. doi: 10.1038/s41467-025-57661-5.
Receptor binding of TGF-β and related ligands such as Activin-A requires cleavage of a furin site in their dimeric precursor proteins. Melanoma cells cleave one Activin-A subunit independently of furin and related proprotein convertases, raising questions of how this half-processed intermediate is generated and whether it influences tumor growth. Here, an siRNA library screen for proteases mediating this furin-independent "hemicleavage" identifies kallikrein (Klk)-8. While a KLK8 cleavage site in proActivin-A overlaps with the furin recognition sequence, its exposure is limited and requires prior transient acidification. Therefore, only furin efficiently converts proActivin-A to fully mature form both in tumor cells and in cell-free cleavage assays. Moreover, knockdown of Klk8 in syngeneic melanoma grafts suppresses Activin-A induced tumor growth, demonstrating that cleavage by only furin is not sufficient. Besides elucidating how Activin-A processing is regulated, our findings show that KLK8 holds promise as a target to mitigate Activin-A induced tumor growth.
转化生长因子-β（TGF-β）以及诸如激活素-A（Activin-A）等相关配体的受体结合需要在其二聚体前体蛋白中切割弗林蛋白酶位点。黑色素瘤细胞独立于弗林蛋白酶及相关前体蛋白转化酶切割一个激活素-A亚基，这引发了关于这种半加工中间体如何产生以及它是否影响肿瘤生长的问题。在此，通过针对介导这种不依赖弗林蛋白酶的“半切割”的蛋白酶进行的小干扰RNA（siRNA）文库筛选，确定了激肽释放酶（Klk）-8。虽然前激活素-A中的Klk8切割位点与弗林蛋白酶识别序列重叠，但其暴露是有限的，并且需要事先短暂酸化。因此，在肿瘤细胞和无细胞切割试验中，只有弗林蛋白酶能有效地将前激活素-A转化为完全成熟的形式。此外，在同基因黑色素瘤移植物中敲低Klk8可抑制激活素-A诱导的肿瘤生长，这表明仅由弗林蛋白酶进行切割是不够的。除了阐明激活素-A加工过程是如何调控的之外，我们的研究结果表明，Klk8有望成为减轻激活素-A诱导的肿瘤生长的靶点。
