Which face of the Golgi apparatus is responsible for receiving vesicles from the ER?
Golgi polarity defined by cis entry face adjacent to ER exit sites and trans exit face oriented toward plasma membrane. Newly synthesized cargo packaged into COPII coated vesicles decorated with Sec23/24 cargo selection and Sar1 GTPase buds from ER after BiP quality control, fuses via TRAPP tethering to ER-Golgi intermediate compartment then to cis Golgi network marked by Rab1 and cis golgin GM130 and GRASP65. Here resident enzymes mannosidase I and N-acetylglucosamine transferase I begin processing, and retrieval of ER proteins via KDEL receptor and COPI retrograde occurs. Medial cisternae continue glycosylation, trans cisternae add galactose sialic acid and sulfation. Finally trans Golgi network defined by clathrin adaptors AP1, GGA sorts cargo to lysosomes or constitutive secretion. Time-lapse tracking of temperature-sensitive VSV-G shows arrival at cis within five minutes from ER release, traversing stacks in about twenty minutes, confirming cis as receiving face. Maturation face term describes cisternal progression model, but receiving function clearly cis, opposite orientation would reverse secretory direction.
Ref: Lippincott-S Cell Bio; COPII ER exit to cis Golgi CGN receives cargo, Rab1, VSV-G trafficking.