Abstract
A Disintegrin and Metalloproteinase with ThromboSpondin motif (ADAMTS) 5 functions as an anti-angiogenic and anti-cancer protein independent of its metalloproteinase activity. Both full-length ADAMTS5 and TS5-p45, the autocatalytically cleaved C-terminal 45 kDa truncate of ADAMTS5, inhibits angiogenesis, and induces endothelial cell (EC) apoptosis. However, how ADAMTS5 triggers EC apoptosis remains unclear. This work shows that caspase-8 (Cas-8) and caspase-9 (Cas-9) are involved in TS5-p45-induced EC apoptosis. We identify cell surface nucleolin (NCL) as a novel high-affinity receptor for TS5-p45 in ECs, mediating TS5-p45’s cell surface binding and pro-apoptotic function. We show that the central RNA-binding domain (RBD) of NCL is essential and sufficient for its binding to TS5-p45. Upon interacting with EC surface NCL, TS5-p45 is internalized through clathrin- and caveolin-dependent endocytosis and trafficked to the nucleus via late endosomes (LEs). We demonstrate that the nuclear trafficking of TS5-p45 is important for its pro-apoptotic activity as disruption of LE membrane integrity with an endosomolytic peptide suppressed both nuclear trafficking and pro-apoptotic activity of TS5-p45. Through cell surface biotinylation, we revealed that cell surface NCL shuttles extracellular TS5-p45 to the nucleus to mediate apoptosis. Furthermore, blocking the importin α1/ß1 receptor hindered the nuclear trafficking of TS5-p45, suggesting the involvement of the nuclear importing machinery for this nuclear translocation. RNA-seq identified many apoptosis-related genes that are differentially expressed at least two-fold in TS5-p45-treated ECs, with 10 of them qRT-PCR-validated and at least 5 of these genes potentially contributing to TS5-p45-NCL-induced apoptosis. Altogether, our work identifies NCL as a novel cell surface receptor for ADAMTS5 and demonstrates the critical role of NCL-mediated internalization and nuclear trafficking for ADAMTS5-induced EC apoptosis. These findings reveal novel mechanistic insights of the secreted metalloproteinase ADAMTS5 in angiogenesis inhibition.
Highlights
Angiogenesis, the formation of new blood vessels from the existing vasculature, is one of the hallmarks of cancer
We further investigated the apoptosis pathways involved in TS5-p45-induced endothelial cell (EC) apoptosis
To check if late endosomes (LEs)-mediated nuclear trafficking of TS5-p45 is important for its pro-apoptotic activity, we examined the impact of L17E on TS5-p45-induced apoptosis
Summary
Angiogenesis, the formation of new blood vessels from the existing vasculature, is one of the hallmarks of cancer. It is essential for tumor growth by supplying nutrients and oxygen and eliminating metabolic waste [1]. A Disintegrin and Metalloproteinase with Thrombospondin Motifs 5 (ADAMTS5), known as aggrecanase-2, is a 100 kDa matrix metalloproteinase of the ADAMTS family. It is the major aggrecanase involved in aggrecan degradation of the articular cartilage in human osteoarthritis [6, 7]. Secreted ADAMTS5 zymogen gets cleaved by furin through extracellular processing to become an active extracellular matrix (ECM) proteinase. ADAMTS5 cleaves other proteoglycans such as brevican (contributing to glioblastoma in brain tissue [10]) and versican (contributing to various vascular diseases [11] and embryonic development [12–14])
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
