Abstract
Golgins are an abundant class of peripheral membrane proteins of the Golgi. These very long (50–400 nm) rod‐like proteins initially capture cognate transport vesicles, thus enabling subsequent SNARE‐mediated membrane fusion. Here, we explore the hypothesis that in addition to serving as vesicle tethers, Golgins may also possess the capacity to phase separate and, thereby, contribute to the internal organization of the Golgi. GM130 is the most abundant Golgin at the cis Golgi. Remarkably, overexpressed GM130 forms liquid droplets in cells analogous to those described for numerous intrinsically disordered proteins with low complexity sequences, even though GM130 is neither low in complexity nor intrinsically disordered. Virtually pure recombinant GM130 also phase‐separates into dynamic, liquid‐like droplets in close to physiological buffers and at concentrations similar to its estimated local concentration at the cis Golgi.
Highlights
The key role of the Golgi apparatus in secretion was firmly established in the 1960s when George Palade and colleagues traced secreted proteins as they traveled from synthesis by ribosomes bound to the ER to the Golgi before reaching secretory storage vesicles [1]
FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies
The Golgin GM130 is a homo-tetramer of ~ 130 kD subunits consisting of four parallel coiled-coil segments with interspersed flexible linkers, and with short nonhelical regions at both its amino and carboxyl-terminal ends (Fig. 1A)
Summary
Golgins are an abundant class of peripheral membrane proteins of the Golgi. These very long (50–400 nm) rod-like proteins initially capture cognate transport vesicles, enabling subsequent SNARE-mediated membrane fusion. We have suggested [8] that they may be a class of abundant cytoplasmically derived proteins termed ‘Golgins’ [14] because these proteins are known to bind Golgi membranes and have similar physical–chemical properties, all being helical bundle-based rods, and because they are located differentially along the cis-trans axis. This latter feature could, in theory, enable internal phase separation to yield Golgi subcompartments, analogous to what has been found for the nucleolus [15]. This raised the interesting possibility that the majority of GM130 could be anchored to the cis face of the Golgi indirectly by condensing with the relatively rare copies that are directly bound to the surface
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