Functional characterisation of the YIPF protein family in mammalian cells.

In this study, we carry out a systematic characterisation of the YIPF family of proteins with respect to their subcellular localisation profile, membrane topology and functional effects on the endomembrane system. YIPF proteins primarily localise to the Golgi complex and can be grouped into trans-Golgi-localising YIPFs (YIPF1 and YIPF2) and cis-Golgi-localising YIPFs (YIPF3, YIPF4 and YIPF5), with YIPF6 and YIPF7 showing a broader profile being distributed throughout the Golgi stack. YIPF proteins have a long soluble N-terminal region, which is orientated towards the cytosol, followed by 5 closely stacked transmembrane domains, and a C terminus, orientated towards the lumen of the Golgi. The significance of YIPF proteins for the maintenance of the morphology of the Golgi was tested by RNA interference, revealing a number of specific morphological changes to this organelle on their depletion. We propose a role for this family of proteins in regulating membrane dynamics in the endomembrane system.