Unconventional secretion: a stress on GRASP.

ABSTRACT

Most proteins follow the classical secretory pathway from the endoplasmic reticulum, via the Golgi, to the plasma membrane or extracellular medium. However, some proteins reach these final destinations by two alternative routes. One sustains the extracellular delivery of cytoplasmic proteins that lack a signal peptide, the other supports the transport of transmembrane proteins to the plasma membrane in a manner that bypasses the Golgi. Here, we highlight the observation that some unconventional secretion events are triggered by cellular stress. Furthermore, one Golgi protein, Golgi Re-Assembly and Stacking Protein (GRASP), has been shown to be essential to both types of unconventional secretion and we discuss ways in which it may support these events in a Golgi-independent manner.