The entry station for all proteins of the secretory path- way (this includes secretory proteins, plasma membrane proteins and proteins destined for various compartments of the endomembrane system) is the endoplasmic reticulum.
The secretory pathway: Mechanisms of protein sorting and transport (PDF Download Available). Available from: https://www.researchgate.net/publication/14547176_The_secretory_pathway_Mechanisms_of_protein_sorting_and_transport [accessed May 1, 2016].