This gene regulates glucose-6-phosphate transport from the cytoplasm to the lumen of the endoplasmic reticulum, in order to maintain glucose homeostasis. It also plays a role in ATP-mediated calcium sequestration in the lumen of the endoplasmic reticulum. Mutations in this gene have been associated with various forms of glycogen storage disease. Alternative splicing in this gene results in multiple transcript variants.[provided by RefSeq, Aug 2009].