Cytosolic Ca2+ Modulates Golgi Structure Through PKCα-Mediated GRASP55 Phosphorylation

Summary It has been well documented that the ER responds to cellular stresses through the unfolded protein response (UPR), but it is unknown how the Golgi responds to similar stresses. In this study, we treated HeLa cells with ER stress inducers, thapsigargin (TG), tunicamycin (Tm), and dithiothreitol (DTT), and found that only TG treatment resulted in Golgi fragmentation. TG induced Golgi fragmentation at a low dose and short time when UPR was undetectable, indicating that Golgi fragmentation occurs independently of ER stress. Further experiments demonstrated that TG induces Golgi fragmentation through elevating intracellular Ca2+ and protein kinase Cα (PKCα) activity, which phosphorylates the Golgi stacking protein GRASP55. Significantly, activation of PKCα with other activating or inflammatory agents, including phorbol 12-myristate 13-acetate and histamine, modulates Golgi structure in a similar fashion. Hence, our study revealed a novel mechanism through which increased cytosolic Ca2+ modulates Golgi structure and function.
Graphical Abstract
Highlights • Thapsigargin (TG) treatment leads to Golgi fragmentation independent of ER stress • TG induces Golgi fragmentation through elevated cytosolic Ca2+ • TG-induced cytosolic Ca2+ spikes activate PKCα that phosphorylates GRASP55 • Histamine modulates the Golgi structure and function by a similar mechanism
Biological Sciences; Cell Biology; Functional Aspects of Cell Biology