Heparanase is an endo-B-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 threedimensional 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.

Molecular and chemical chaperones are key components of the two main mechanisms that ensure structural stability and activity under environmental stresses. Yet, chemical chaperones are often regarded only as osmolytes and their role beyond osmotic regulation is not fully understood. Here, we systematically studied a large group of chemical chaperones, representatives of diverse chemical families, for their protective influence under either thermal or chemical stresses. Consistent with previous studies, we observed that in spite of the structural similarity between sugars and sugar alcohols, they have an apparent difference in their protective potential. Our results support the notion that the protective activity is mediated by the solvent and the presence of water is essential. In the current work we revealed that i) polyols and sugars have a completely different profile of protective activity toward trifluoroethanol and thermal stress; ii) minor changes in solvent composition that do not affect enzyme activity, yet have a great effect on the ability of osmolytes to act as protectants and iii) increasing the number of active groups of carbohydrates makes them better protectants while increasing the number of active groups of methylamines does not, as revealed by attempts to synthesize de novo designed methylamines with multiple functional groups.

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Supplementary Figure 1 from Structure-Function Approach Identifies a COOH-Terminal Domain That Mediates Heparanase Signaling

Supplementary Figure Legends 1-2 from Structure-Function Approach Identifies a COOH-Terminal Domain That Mediates Heparanase Signaling