Structure-function approach identifies a COOH-terminal domain that mediates heparanase signaling.
Heparanase is an endo-beta-d-glucuronidase capable of cleaving heparan sulfate, activity that is strongly implicated in cellular invasion associated with tumor metastasis, angiogenesis, and inflammation. In addition, heparanase was noted to exert biological functions apparently independent of its enzymatic activity, enhancing the phosphorylation of selected protein kinases and inducing gene transcription. A predicted three-dimensional structure of constitutively active heparanase clearly delineates a TIM-barrel fold previously anticipated for the enzyme. Interestingly, the model also revealed the existence of a COOH-terminal domain (C-domain) that apparently is not an integral part of the TIM-barrel fold. We provide evidence that the C-domain is critical for heparanase enzymatic activity and secretion. Moreover, the C-domain was found to mediate nonenzymatic functions of heparanase, facilitating Akt phosphorylation, cell proliferation, and tumor xenograft progression. These findings support the notion that heparanase exerts enzymatic activity-independent functions, and identify, for the first time, a protein domain responsible for heparanase-mediated signaling. Inhibitors directed against the C-domain, combined with inhibitors of heparanase enzymatic activity, are expected to neutralize heparanase functions and to profoundly affect tumor growth, angiogenesis, and metastasis.
Fux
Liat
L
Cancer and Vascular Biology Research Center, The Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel.
Feibish
Nir
N
Cohen-Kaplan
Victoria
V
Gingis-Velitski
Svetlana
S
Feld
Sari
S
Geffen
Chen
C
Vlodavsky
Israel
I
Ilan
Neta
N
D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005260:Female; D005966:Glucuronidase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000502:physiology*; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D018613:Microscopy, Confocal; D008958:Models, Molecular; D009374:Neoplasms, Experimental / Q000209:etiology; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D000099175:Heparanase
D005966:Glucuronidase; D051057:Proto-Oncogene Proteins c-akt; D000099175:Heparanase