The SLC37A4 transport protein in the endoplasmic reticulum membrane normally mediates the exchange of cytosolic glucose-6-phosphate and orthophosphate from the endoplasmic reticulum lumen. Defects in this transporter are associated with glycogen storage disease type Ib. The two missense mutant forms of SLC37A4 annotated here are examples of the many that have been described (Gerin et al. 1997; Chen et al. 2008; Veiga-da-Cunha et al. 1998).

The SLC37A4 transport protein in the endoplasmic reticulum membrane mediates the exchange of cytosolic G6P (glucose-6-phosphate) and Pi (orthophosphate) from the endoplasmic reticulum lumen. Defects in this transporter are associated with glycogen storage disease type Ib (Gerin et al. 1997; Chen et al. 2008; Veiga-da-Cunha et al. 1998).

The SLC37A4 transport protein in the endoplasmic reticulum membrane normally mediates the exchange of cytosolic glucose-6-phosphate and orthophosphate from the endoplasmic reticulum lumen. Defects in this transporter are associated with glycogen storage disease type Ib (Gerin et al. 1997; Chen et al. 2008; Veiga-da-Cunha et al. 1998).

The regulated turnover of glycogen plays a central, tissue-specific role in the maintenance of blood glucose levels and in the provision of glucose to tissues such as muscle and brain in response to stress. Defects in the enzymes involved in glycogen turnover are associated with abnormal responses to fasting and exercise that can differ widely in their presentation and severity. Additional symptoms can be the result of accumulation of abnormal products of glycogen metabolism (Hauk et al. 1959; Hers 1964; Shin 2006). Annotations are provided here for diseases due to deficiencies of GYS1 and GYS1 (glycogen synthase 1 and 2; glycogen storage disease type 0 (GSD type 0), of G6PC (glucose-6-phosphatase, GSD type Ia) and the SLC37A4 transporter (GSD type Ib), of GAA (lysosomal acid alpha-glucosidase, GSD type II), of GBE1 (glycogen branching enzyme, GSD type IV), and of GYG1 (glycogenin 1, GSD XV). Two additional diseases, myoclonic epilepsy of Lafora (Roach et al. 2012) and severe congenital neutropenia type 4 (Boztug et al. 2009), are included as they are due to defects in enzymes of glycogen metabolism.

Glucose-6-phosphate exchanger SLC37A4.