AP4S1

AP-4 complex subunit sigma-1 is a is_associated_with::protein that in humans is encoded by the AP4S1 is_associated_with::gene.

Function
The is_associated_with::heterotetrameric adaptor protein (AP) complexes sort integral membrane proteins at various stages of the endocytic and secretory pathways. AP4 is composed of 2 large chains, beta-4 (is_associated_with::AP4B1) and epsilon-4 (is_associated_with::AP4E1), a medium chain, mu-4 (is_associated_with::AP4M1), and a small chain, sigma-4 (AP4S1, this gene).

Clinical relevance
It is currently hypothesized that AP4-complex-mediated trafficking plays a crucial role in brain development and functioning.