Boca, an endoplasmic reticulum protein required for wingless signaling and trafficking of LDL receptor family members in Drosophila.

The maturation of cell surface receptors through the secretory pathway often requires chaperones that aid in protein folding and trafficking from one organelle to another. Here we describe boca, an evolutionarily conserved gene in Drosophila melanogaster, which encodes an endoplasmic reticulum protein that is specifically required for the intracellular trafficking of members of the low-density lipoprotein family of receptors (LDLRs). Two LDLRs in flies, Arrow, which is required for Wingless signal transduction, and Yolkless, which is required for yolk protein uptake during oogenesis, both require boca function. Consequently, boca is an essential component of the Wingless pathway but is more generally required for the activities of multiple LDL receptor family members.