VIP21, a 21-kD membrane protein is an integral component of trans-Golgi-network-derived transport vesicles.

TLDR

In simple epithelial cells, apical and basolateral proteins are sorted into distinct vesicular carriers before reaching their respective plasma membrane domains. The study aims to dissect the sorting machinery of Golgi-derived vesicles and to identify VIP21 as a component of the vesicular transport machinery. Golgi-derived transport vesicles were solubilized with CHAPS, revealing that influenza HA forms a large complex with several integral membrane proteins. A CHAPS‑insoluble protein complex, including VIP21, was identified, cloned, and shown to localize to the Golgi, plasma membrane, and vesicular structures.

Abstract

In simple epithelial cells, apical and basolateral proteins are sorted into separate vesicular carriers before delivery to the appropriate plasma membrane domains. To dissect the putative sorting machinery, we have solubilized Golgi-derived transport vesicles with the detergent CHAPS and shown that an apical marker, influenza haemagglutinin (HA), formed a large complex together with several integral membrane proteins. Remarkably, a similar set of CHAPS-insoluble proteins was found after solubilization of a total cellular membrane fraction. This allowed the cloning of a cDNA encoding one protein of this complex, VIP21 (Vesicular Integral-membrane Protein of 21 kD). The transiently expressed protein appeared on the Golgi-apparatus, the plasma membrane and vesicular structures. We propose that VIP21 is a component of the molecular machinery of vesicular transport.