David Gill1, Joanne Chia1, Jamie Senewiratne1 and Frederic Bard1,2
1 – Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673
2 – National University of Singapore, 21 Lower Kent Ridge Road, Singapore 119077
Published in J Cell Biol. 2010 May 24. [Epub ahead of print]
Following growth factor stimulation, kinases are activated to regulate multiple aspects of cell physiology. Activated Src is present on Golgi membranes but its function here remains unclear. We find that Src regulates mucin-type protein O-glycosylation through redistribution of the initiating enzymes, polypeptide N-acetylgalactosaminyl transferases (GalNac-Ts), from the Golgi to the ER. Redistribution occurs after stimulation with EGF or PDGF in a Src dependent manner and in cells with constitutively elevated Src activity. All GalNac-T family enzymes tested are affected whereas multiple other glycosylation enzymes are not displaced from the Golgi. Upon Src activation, the COP-I coat is also redistributed in punctate structures that co-localize with GalNac-Ts and a dominant negative Arf1 isoform, Arf1(Q71L), efficiently blocks GalNac-Ts redistribution, indicating that Src activates a COP-I dependent trafficking event. Finally, Src activation increases O-glycosylation initiation as seen by lectin staining and metabolic labeling. We propose that growth factor stimulation regulates O-glycosylation initiation in a Src dependent fashion by GalNac-Ts redistribution to the ER.