p115 untethered

Sometimes the simplest, most elegant hypothesis is correct. And sometimes it is not. On page 227, Puthenveedu and Linstedt poke holes in a hypothesis that has been used to explain how the Golgi is vesiculated for distribution during mitosis. In the process they invoke a new, essential function for the p115 protein in the earliest steps of Golgi formation.

The p115 protein forms part of a tether that leads from GRASP65 on Golgi membranes, through GM130 and then p115, and finally to the integral membrane protein giantin on vesicles. Loss of this link in the presence of continued vesicle formation could lead to vesiculation of the Golgi, and indeed during mitosis GM130 is phosphorylated, such that it no longer binds p115. Consistent with this theory, Puthenveedu and Linstedt find that the injection of p115 antibodies results in...