9.B.207 The Starch-binding Domain-containing Protein, Stbd1 (Stbd1) Family
A small fraction of cellular glycogen is transported to and degraded in lysosomes by acid α-glucosidase (GAA) in mammals. Stbd1 may participate in glycogen trafficking to lysosomes. In GAA/Stbd1 double knockout mice, glycogen accumulation in skeletal and cardiac muscles was not affected, but glycogen content in liver was reduced by 73% at age of 3 months and 60% at 13 months compared with GAA knockout mice, indicating that the transport of glycogen to lysosomes was suppressed in liver by the loss of Stbd1. Exogenous expression of human Stbd1 in KO mice restored the liver lysosomal glycogen content to the level of GAA knockout mice. The results suggest that Stbd1 plays a role in glycogen transport to lysosomes in liver. The N-terminal transmembrane region and the C-terminal CBM20 domain seem to be critical for this function (Sun et al. 2016). Stbd1 has 358 aas and a lingle N-terminal TMS.