Figure 1. Diagrammatical representation of the intracellular transport of glycoproteins along endocytic and exocytic pathways.

Internalization of cell surface glycoproteins occurs by clathrin-mediated, caveolin-mediated, or clathrin- & caveolinindependent pathways, followed by the fusion of internalized vesicles with early endosomes where the cargo is sorted and targeted for either recycling (from trans-Golgi, late endosome and recycling endosome) or for degradation (in lysosomes). The other exocytic route are representative of the secretory pathways, where glycoproteins are first synthesized and processed in the rough ER followed by their entry into the Golgi, where they are further modified, packaged into secretory vesicles (SV) and either targeted to the plasma membrane or secreted by the exocytic machinery.

Abbreviations: EE, early endosome; RE, recycling endosome; MBMs, membrane bound mucins; SMs, secretory mucins; SV, secretory vesicles; SG, secretory granules; EC, extracellular