Processing of heparanase is mediated by syndecan-1 cytoplasmic domain and involves syntenin and α-actinin.
Heparanase activity plays a decisive role in cell dissemination associated with cancer metastasis. Cellular uptake of heparanase is considered a pre-requisite for the delivery of latent 65-kDa heparanase to lysosomes and its subsequent proteolytic processing and activation into 8- and 50-kDa protein subunits by cathepsin L. Heparan sulfate proteoglycans, and particularly syndecan, are instrumental for heparanase uptake and activation, through a process that has been shown to occur independent of rafts. Nevertheless, the molecular mechanism underlying syndecan-mediated internalization outside of rafts is unclear. Here, we examined the role of syndecan-1 cytoplasmic domain in heparanase processing, utilizing deletion constructs lacking the entire cytoplasmic domain (Delta), the conserved (C1 or C2), or variable (V) regions. Heparanase processing was markedly increased following syndecan-1 over-expression; in contrast, heparanase was retained at the cell membrane and its processing was impaired in cells over-expressing syndecan-1 deleted for the entire cytoplasmic tail. We have next revealed that conserved domain 2 (C2) and variable (V) regions of syndecan-1 cytoplasmic tail mediate heparanase processing. Furthermore, we found that syntenin, known to interact with syndecan C2 domain, and α actinin are essential for heparanase processing.
Cancer and Vascular Biology Research Center, the Bruce Rappaport Faculty of Medicine, Technion, 9649, 31096, Haifa, Israel.
Anna
A
Shteingauz
Neta
N
Ilan
Israel
I
Vlodavsky
D000185:Actinin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D005966:Glucuronidase / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D053668:Syndecan-1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D053676:Syntenins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000099175:Heparanase
D000185:Actinin; D005966:Glucuronidase; D034741:RNA, Small Interfering; D053668:Syndecan-1; D053676:Syntenins; D000099175:Heparanase