Roles of Ca2+ and secretory pathway Ca2+-ATPase pump type 1 (SPCA1) in intra-Golgi transport

Abstract

Mechanisms for intra-Golgi transport remain a hotly debated topic. Recently, we published data illuminating a new aspect involved in intra-Golgi transport, namely a release of free cytosolic Ca2+ ([Ca2+]cyt) from the lumen of Golgi cisternae that is fundamental for the secretion and the progression of newly synthesized proteins through the Golgi apparatus (GA). This increase in [Ca2+]cyt during the late stage of synchronous intra-Golgi transport stimulates the fusion of membranes containing cargo proteins and Golgi cisternae, allowing the progression of proteins through the GA. Subsequent restoration of the basal [Ca2+]cyt is also important for the delivery of cargo to the proper final destination. Additionally, the secretory pathway Ca2+-ATPase Ca2+ pump (SPCA1) plays an essential role at this stage. The fine regulation of membrane fusion is also important for the formation and the maintenance of the Golgi ribbon and SPCA1, which regulates [Ca2+]cyt levels, can be considered a controller of trafficking. This evidence contradicts a model of intra-Golgi transport in which permanent membrane continuity allows cargo diffusion and progression. © 2010 Landes Bioscience.