Pi-Wan Cheng, PhD

Professor

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Phone: 402-559-5776

The research focus of Pi-Wan Cheng, PhD, and his laboratory is to elucidate the fundamental mechanism of glycosylation to help understand how glycosylation is altered in various diseases, including cancer progression. Recently, his team has identified the Golgi targeting sites of glycosyltransferases, the Golgi retention proteins for some of them, and the roles of non-muscle myosin IIA in recycling of glycosyltransferases and Golgi fragmentation.

They have found that giantin is the primary targeting site for all glycosyltransferases and mannosidases except core 1 synthase and core 2 enzymes only use this site for Golgi targeting. Core 1 synthase uses GM130-GRASAP65 as the primary targeting site and GM130-giantin as the targeting site when GRASP65 is not available. When giantin is defective as is seen in aggressive cancer cells and cells under stress, core 2 enzymes cannot get to the Golgi and are degraded, and all other glycosyltransferases and mannosidases still can reach the Golgi using GM130-GRASP65. The dysregulated glycosylation environment at the GM130-GRASP65 site results in altered glycosylation, such as formation of high mannose N-glycans and tumor-associated carbohydrate antigens of mucin O-glycans (Figure 1). These altered glycans are being developed as biomarkers and therapeutic targets of aggressive cancers.

Mechanism of altered glycosylation in advanced cancers: Defective Giantin prevents Golgi targeting of Core2 enzymes (C2GnTs) and causes a shift of Golgi targeting of other glycosylation enzymes to GM130-GRA P65 site, which can be reversed by treatment with Blebbistatin (Blebb) as mediated by Rab6a, polo-like kinase 3, and protein disulfide isom erase A3.