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

Figures & data

Figure 1 Schematic representation of the (sub)compartmental distribution of SPCA1 along the secretory pathway. SPCA1 is prevalent on the lateral rims of the Golgi cisternae, in the most cis- and trans-Golgi and on the endo/lysosomal compartment, but not on ER membranes. SERCA is typically present on ER membranes and overlapping with SPCA1 distribution only in the most cis-Golgi (ERGiC and cis-Golgi). The arrival of cargo to the GA induces the release of Ca²⁺ from the IP₃R which induces a relocation on the GA of membrane remodeling enzymes (i.e., cPLA₂) as well as calmodulin (CaM) and SNARE cofactors Ca²⁺-sensitive; this redistribution is crucial to orchestrate the SNARE fusion machinery which coordinates the fusion events necessary for the protein trafficking through the GA. Subsequently, the restoration of the basal [Ca²⁺]_cyt requires the activation of the SPCA1, that transfers the increased [Ca²⁺]_cyt into the GA lumen. The diluted colors from the darker ER to the clearest TGN indicates decreasing lumenal [Ca²⁺].