Identifying Snapin as the co-acting protein with heparanase, a key enzyme in metastasis

YJ Li MD^a,b, JX Li MD^a,c, HC Zhu BS^b, YL Lin MS^b, GY Tang MS^b, QZ Peng PhD^b, LD Wang MD^a

^aLaboratory for Cancer Research, College of Medicine, Zhengzhou University, Zhengzhou, China, ^bAcademy of Military Medical Sciences, Beijing, China, ^clife science college, Henan Normal University, Xinxiang, China

AIM: Heparanase, one of the β-D-endoglucuronidases, has higher expression in various human tumors as compared to the normal tissues. By degrading heparan sulfate in the extracellular matrix, it contributes to tumor invasion and metastasis. However, the regulation mechanism of its enzymatic activity is still elusive. Seeking the interactors of the enzyme may cast light on the actual processes of its localization, transporting, activation and regulation. We perform the present study to identify the potential interactors with heparanase. METHODS: The full encoding gene of heparanase was amplified by PCR from the cDNA library of human placenta. Before served as the bait protein, no self-activation was verified on heparanase. The human placental pre-transformed cDNA library was sreened by the yeast two hybrid for the potential binding proteins. The rough region of the binding domain was located by deleted construction. The specific binding was further confirmed using coimmunoprecipitation. RESULTS: From the screen, we identified an heparanase binding protein, Snapin, a protein located on synaptic vesicle membrane and closely related with membrane fusion. Snapin plays an important role in regulating in docking and fusing of vesicles and plasma membrane as well as releasing the contents of vesicles. Furthermore, we located the interacting domain with Snapin to the C-terminus 50KD unit of heparanase. CONCLUSIONS: The results suggested that heparanase may physiologically locate or be stored in synaptic vesicles and be transported to targeted vesicles through its interaction with Snapin. The synaptic vesicle exocytosis of heparanase may be regulated by snapin in certain environment. Snapin potentially play an important role in the regulation of heparanase enzymatic activity. Further understanding the control of heparanase routing, secretion in tumor cells might offer the mechanism of heparanase upregulaion in proangiogenic and prometastatic tumors.

Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Nice, France; February 7 - 10, 2004; in poster session 996 (Genetic & environmental interactions).