O-linked N-acetylglucosamine glycosylations (O-GlcNAc) and O-linked phosphorylations (O-phosphate), as two important types of post-translational modifications, often occur on the same protein and bear a reciprocal relationship. In addition to the well documented phosphorylations that control Akt activity, Akt also undergoes O-GlcNAcylation, but the interplay between these two modifications and the biological significance remain unclear, largely due to the technique challenges. Here, we applied a two-step analytic approach composed of the O-GlcNAc immunoenrichment and subsequent O-phosphate immunodetection. Such an easy method enabled us to visualize endogenous glycosylated and phosphorylated Akt subpopulations in parallel and observed the inhibitory effect of Akt O-GlcNAcylations on its phosphorylation. Further studies utilizing mass spectrometry and mutagenesis approaches showed that O-GlcNAcylations at Thr 305 and Thr 312 inhibited Akt phosphorylation at Thr 308 via disrupting the interaction between Akt and PDK1. The impaired Akt activation in turn resulted in the compromised biological functions of Akt, as evidenced by suppressed cell proliferation and migration capabilities. Together, this study revealed an extensive crosstalk between O-GlcNAcylations and phosphorylations of Akt and demonstrated O-GlcNAcylation as a new regulatory modification for Akt signaling.

Purpose: Recent epidemiological and clinical studies have suggested the benefit of aspirin for patients with cancer, which inspired increasing efforts to demonstrate the anticancer ability of aspirin and reveal the molecular mechanisms behind. Nevertheless, the anticancer activity and related mechanisms of aspirin remain largely unknown. This study aimed to confirm this observation, and more importantly, to investigate the potential target contributed to the anticancer of aspirin.Experimental Design: A homogeneous time-resolved fluorescence (HTRF) assay was used to examine the impact of aspirin on heparanase. Streptavidin pull-down, surface plasmon resonance (SPR) assay, and molecular docking were performed to identify heparanase as an aspirin-binding protein. Transwell, rat aortic rings, and chicken chorioallantoic membrane model were used to evaluate the antimetastasis and anti-angiogenesis effects of aspirin, and these phenotypes were tested in a B16F10 metastatic model, MDA-MB-231 metastatic model, and MDA-MB-435 xenograft model.Results: This study identified heparanase, an oncogenic extracellular matrix enzyme involved in cancer metastasis and angiogenesis, as a potential target of aspirin. We had discovered that aspirin directly binds to Glu225 region of heparanase and inhibits the enzymatic activity. Aspirin impeded tumor metastasis, angiogenesis, and growth in heparanase-dependent manner.Conclusions: In summary, this study has illustrated heparanase as a target of aspirin for the first time. It provides insights for a better understanding of the mechanisms of aspirin in anticancer effects, and offers a direction for the development of smallmolecule inhibitors of heparanase.

Background: O-GlcNAcylation plays important roles in breast cancer metastasis, but the underlying mechanism is not fully known. Results: Cofilin is O-GlcNAcylated at Ser-108, which is required for its proper localization in invadopodia and is implicated in promoting breast cancer cell invasion. Conclusion: O-GlcNAcylation plays an important role in fine-tuning the regulation of cofilin. Significance: These findings reveal the implications of aberrant cofilin O-GlcNAcylation in cancer metastasis.