Characterization of a novel UDP-GalNAc:polypeptide N-acetyl galactosaminyl transferase that is essential for viability in Drosophila

Wednesday, October 10, 2012 — Poster Session II
Noon – 2:00 p.m	Natcher Conference Center, Building 45	NIDCR	DEV-7

Authors

• S. Ji
• E Tian
• K.G. Ten Hagen

Abstract

Mucin-type O-linked glycosylation is abundant in the extracellular matrix and is initiated in the Golgi by the UDP-GalNAc:polypeptide N-acetylgalactosaminyl transferase family of enzymes (pGalNAc-T in mammals and PGANT in Drosophila), which adds a GalNAc sugar to serines or threonines of secreted and membrane-bound proteins. In Drosophila, there are nine PGANTs (PGANT1-8, PGANT35A) and three putative PGANT isoforms. CG30463 is one putative PGANT isoform based on sequence conservation. Knockdown of CG30463 via RNA interference (RNAi) in vivo results in lethality, indicating that CG30463 is an essential gene. However, the catalytic activity of the enzyme encoded by CG30463 had not been identified previously. Here, we demonstrate that CG30463 encodes a functional O-glycosyltransferase, PGANT9. Purified PGANT9 protein transferred GalNAc onto both peptide and glycopeptide substrates in vitro. Additionally, over-expression of PGANT9 in cell culture increased HPA-reactive glycosylation in vivo. Interestingly, tissue-specific knockdown of PGANT9 in vivo showed several phenotypes, including reduced salivary gland size, abnormal digestive system formation, and irregular eye cell arrangement. Our studies demonstrate that the essential gene CG30463 is a functional O-glycosyltransferase and implicates its activity in the proper development of the salivary gland, digestive system and eye in Drosophila.

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