The protein is originally synthesised in an inactive 65 kDa proheparanase form in the golgi apparatus and transferred to late endosomes/lysosomes for transport to the cell-surface. In the lysosome it is proteolytically processed into its active form. Proteolytic processing results in the production of three products,
a linker peptide
an 8 kDa proheparanase fragment and
a 50 kDa proheparanase fragment
The 8 kDa and 50 kDa fragments form a heterodimer and it is this heterodimer that constitutes the active heparanase molecule.[7] The linker protein is so called because prior to its excision it physically links the 8 kDa and 50 kDa proheparanase fragments. Complete excision of the linker peptide appears to be a prerequisite to the complete activation of the heparanase enzyme.
Crystal structures of both proheparanase and mature heparanase are available, showing that the linker peptide forms a large helical domain which blocks heparan sulfate molecules from interacting with heparanase.[8] Removal of the linker reveals an extended cleft on the enzyme surface, which contains the heparanase active site.[9]
Function
Heparanase has endoglycosidase activity and cleaves polymeric heparan sulfate molecules at sites which are internal within the polymeric chain.[10] The enzyme degrades the heparan sulfate scaffold of the basement membrane and extracellular matrix. It is also associated with the inflammatory process, by allowing the extravasation of activated T lymphocytes.[11] In ocular surface physiology this activity functions as an off/on switch for the prosecretory mitogen lacritin. Lacritin binds the cell surface heparan sulfate proteoglycan syndecan-1 only in the presence of active heparanase. Heparanase partially or completely cleaves heparan sulfate to expose a binding site in the N-terminal 50 amino acids of syndecan-1.[12]
Clinical significance
The successful penetration of the endothelial cell layer that lines the interior surface of blood vessels is an important process in the formation of blood borne tumour metastases. Heparan sulfateproteoglycans are major constituents of this layer and it has been shown that increased metastatic potential corresponds with increased heparanase activity for a number of cell lines.[13][14] Due to the contribution of heparanase activity to metastasis and also to angiogenesis, the inhibition of heparanase activity it is considered to be a potential target for anti-cancer therapies.[15][16]
Heparanase has been shown to promote arterial thrombosis and stent thrombosis in mouse models due to the cleavage of anti-coagulant heparan sulfateproteoglycans.[17]
^"Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^"Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^Vlodavsky I, Friedmann Y, Elkin M, Aingorn H, Atzmon R, Ishai-Michaeli R, Bitan M, Pappo O, Peretz T, Michal I, Spector L, Pecker I (July 1999). "Mammalian heparanase: gene cloning, expression and function in tumor progression and metastasis". Nature Medicine. 5 (7): 793–802. doi:10.1038/10518. PMID10395325. S2CID38895589.
^Hulett MD, Freeman C, Hamdorf BJ, Baker RT, Harris MJ, Parish CR (July 1999). "Cloning of mammalian heparanase, an important enzyme in tumor invasion and metastasis". Nature Medicine. 5 (7): 803–9. doi:10.1038/10525. PMID10395326. S2CID20125382.
^Vlodavsky I, Ilan N, Naggi A, Casu B (2007). "Heparanase: structure, biological functions, and inhibition by heparin-derived mimetics of heparan sulfate". Curr. Pharm. Des. 13 (20): 2057–2073. doi:10.2174/138161207781039742. PMID17627539.
^Vlodavsky I, Goldshmidt O, Zcharia E, Atzmon R, Rangini-Guatta Z, Elkin M, Peretz T, Friedmann Y (2003). "Mammalian heparanase: involvement in cancer metastasis, angiogenesis and normal development". Seminars in Cancer Biology. 12 (2): 121–9. doi:10.1006/scbi.2001.0420. PMID12027584.
Zcharia E, Metzger S, Chajek-Shaul T, Friedmann Y, Pappo O, Aviv A, Elkin M, Pecker I, Peretz T, Vlodavsky I (2002). "Molecular properties and involvement of heparanase in cancer progression and mammary gland morphogenesis". Journal of Mammary Gland Biology and Neoplasia. 6 (3): 311–22. doi:10.1023/A:1011375624902. PMID11547900. S2CID13292455.
Vlodavsky I, Abboud-Jarrous G, Elkin M, Naggi A, Casu B, Sasisekharan R, Ilan N (2006). "The impact of heparanese and heparin on cancer metastasis and angiogenesis". Pathophysiol. Haemost. Thromb. 35 (1–2): 116–27. doi:10.1159/000093553. PMID16855356. S2CID25204783.
Maruyama K, Sugano S (1994). "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene. 138 (1–2): 171–4. doi:10.1016/0378-1119(94)90802-8. PMID8125298.
Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, Suyama A, Sugano S (1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene. 200 (1–2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID9373149.
Vlodavsky I, Friedmann Y, Elkin M, Aingorn H, Atzmon R, Ishai-Michaeli R, Bitan M, Pappo O, Peretz T, Michal I, Spector L, Pecker I (1999). "Mammalian heparanase: gene cloning, expression and function in tumor progression and metastasis". Nat. Med. 5 (7): 793–802. doi:10.1038/10518. PMID10395325. S2CID38895589.
Hulett MD, Freeman C, Hamdorf BJ, Baker RT, Harris MJ, Parish CR (1999). "Cloning of mammalian heparanase, an important enzyme in tumor invasion and metastasis". Nat. Med. 5 (7): 803–9. doi:10.1038/10525. PMID10395326. S2CID20125382.
Kussie PH, Hulmes JD, Ludwig DL, Patel S, Navarro EC, Seddon AP, Giorgio NA, Bohlen P (1999). "Cloning and functional expression of a human heparanase gene". Biochem. Biophys. Res. Commun. 261 (1): 183–7. doi:10.1006/bbrc.1999.0962. PMID10405343.
Dong J, Kukula AK, Toyoshima M, Nakajima M (2000). "Genomic organization and chromosome localization of the newly identified human heparanase gene". Gene. 253 (2): 171–8. doi:10.1016/S0378-1119(00)00251-1. PMID10940554.
Hulett MD, Hornby JR, Ohms SJ, Zuegg J, Freeman C, Gready JE, Parish CR (2001). "Identification of active-site residues of the pro-metastatic endoglycosidase heparanase". Biochemistry. 39 (51): 15659–67. doi:10.1021/bi002080p. PMID11123890.
Ginath S, Menczer J, Friedmann Y, Aingorn H, Aviv A, Tajima K, Dantes A, Glezerman M, Vlodavsky I, Amsterdam A (2001). "Expression of heparanase, Mdm2, and erbB2 in ovarian cancer". Int. J. Oncol. 18 (6): 1133–44. doi:10.3892/ijo.18.6.1133. PMID11351242.
Koliopanos A, Friess H, Kleeff J, Shi X, Liao Q, Pecker I, Vlodavsky I, Zimmermann A, Büchler MW (2001). "Heparanase expression in primary and metastatic pancreatic cancer". Cancer Res. 61 (12): 4655–9. PMID11406531.
Nadav L, Eldor A, Yacoby-Zeevi O, Zamir E, Pecker I, Ilan N, Geiger B, Vlodavsky I, Katz BZ (2003). "Activation, processing and trafficking of extracellular heparanase by primary human fibroblasts". J. Cell Sci. 115 (Pt 10): 2179–87. doi:10.1242/jcs.115.10.2179. PMID11973358.
External links
Overview of all the structural information available in the PDB for UniProt: Q9Y251 (Heparanase) at the PDBe-KB.
