GOPC facilitates the sorting of syndecan-1 in polarized epithelial cells

The trans-Golgi network must coordinate sorting and secretion of proteins and lipids to intracellular organelles and the plasma membrane. During polarization of epithelial cells, changes in the lipidome and the expression and distribution of proteins contribute to the formation of apical and basolateral plasma membrane domains. Previous studies using HeLa cells show that the syndecan-1 transmembrane domain confers sorting within sphingomyelin-rich vesicles in a sphingomyelin secretion pathway. In polarized Madin-Darby canine kidney cells, we reveal differences in the sorting of syndecan-1, whereupon the correct trafficking of the protein is not dependent on its transmembrane domain and changes in sphingomyelin content of cells during polarization. Instead, we reveal that correct basolateral targeting of syndecan-1 requires a full-length PDZ motif in syndecan-1 and the PDZ domain golgin protein GOPC. Moreover, we reveal changes in Golgi morphology elicited by GOPC overexpression. These results suggest that the role of GOPC in sorting syndecan-1 is indirect and likely due to GOPC effects on Golgi organization.

Automated summary

The trans-Golgi network plays a crucial role in the polarization of epithelial cells by coordinating the sorting and secretion of proteins and lipids. This study investigates the sorting of syndecan-1 in different cell types and reveals that its basolateral targeting is dependent on the presence of a full-length PDZ motif and the PDZ domain golgin protein GOPC. The study also uncovers changes in Golgi morphology induced by GOPC overexpression, suggesting that GOPC affects the Golgi organization and indirectly influences the sorting of syndecan-1.