Cathepsin K cleavage of SDF-1α inhibits its chemotactic activity towards glioblastoma stem-like cells
Glioblastoma (GBM) is the most aggressive primary brain tumor with poor patient survival that is at least partly caused by malignant and therapy-resistant glioma stem-like cells (GSLCs) that are protected in GSLC niches. Previously, we have shown that the chemo-attractant stromal-derived factor-1α (SDF-1α), its C-X-C receptor type 4 (CXCR4) and the cysteine protease cathepsin K (CatK) are localized in GSLC niches in glioblastoma. Here, we investigated whether SDF-1α is a niche factor that through its interactions with CXCR4 and/or its second receptor CXCR7 on GSLCs facilitates their homing to niches. Furthermore, we aimed to prove that SDF-1α cleavage by CatK inactivates SDF-1α and inhibits the invasion of GSLCs. We performed mass spectrometric analysis of cleavage products of SDF-1α after proteolysis by CatK. We demonstrated that CatK cleaves SDF-1α at 3 sites in the N-terminus, which is the region of SDF-1α that binds to its receptors. Confocal imaging of human GBM tissue sections confirmed co-localization of SDF-1α and CatK in GSLC niches. In accordance, 2D and 3D invasion experiments using CXCR4/CXCR7-expressing GSLCs and GBM cells showed that SDF-1α had chemotactic activity whereas CatK cleavage products of SDF-1α did not. Besides, CXCR4 inhibitor plerixafor inhibited invasion of CXCR4/CXCR7-expressing GSLCs. In conclusion, CatK can cleave and inactivate SDF-1α. This implies that CatK activity facilitates migration of GSLCs out of niches. We propose that activation of CatK may be a promising strategy to prevent homing of GSLCs in niches and thus render these cells sensitive to chemotherapy and radiation.
Cathepsin K, Glioma stem-like cells, Niche, Stromal-derived factor-1α
Medical Subject Headings
Amino Acid Sequence; Benzylamines; Cathepsin K (genetics, metabolism); Cell Line, Tumor; Chemokine CXCL12 (chemistry, genetics, metabolism); Chemotaxis; Cyclams; Gene Expression; Heterocyclic Compounds (pharmacology); Humans; Neoplastic Stem Cells (metabolism, pathology); Neuroglia (metabolism, pathology); Protein Binding; Protein Conformation, alpha-Helical; Protein Conformation, beta-Strand; Proteolysis; Receptors, CXCR (genetics, metabolism); Receptors, CXCR4 (antagonists & inhibitors, genetics, metabolism); Stem Cell Niche (genetics)
Biochimica et biophysica acta. Molecular cell research
Digital Object Identifier (DOI)
Hira, Vashendriya V.; Verbovšek, Urška; Breznik, Barbara; Srdič, Matic; Novinec, Marko; Kakar, Hala; Wormer, Jill; der Swaan, Britt Van; Lenarčič, Brigita; Juliano, Luiz; Mehta, Shwetal; Van Noorden, Cornelis J.; and Lah, Tamara T., "Cathepsin K cleavage of SDF-1α inhibits its chemotactic activity towards glioblastoma stem-like cells" (2017). Translational Neuroscience. 1584.