Golgi phosphoprotein 3 mediates the Golgi localization and function of protein O-linked mannose {beta}-1,2-Nacetlyglucosaminyltransferase 1 [Cell Biology]

April 14th, 2014 by Pereira, N. A., Pu, H. X., Goh, H., Song, Z.

GOLPH3 is a highly conserved protein found across the eukaryotic lineage. The yeast homologue, Vps74p, interacts with and maintains the Golgi localization of several mannosyltransferases, which is subsequently critical for N- and O- glycosylation in yeast. Here, T7 phage display was used to screen for novel interacting partners of GOLPH3. GOLPH3 was found to bind to POMGnT1 which is involved in O-mannosylation of α-dystroglycan. We found that loss of this interaction resulted in the inability of POMGnT1 to localize to the Golgi and reduced the functional glycosylation of α-dystroglycan. In addition, we showed that three clinically relevant mutations in POMGnT1 mislocalized to the ER highlighting the importance of identifying the molecular mechanisms responsible for Golgi localization of glycosyltransferases. Our findings reveal a novel role for GOLPH3 in mediating the Golgi localization of POMGnT1.
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