Chaperone specifically assisting the folding of beta-propeller/EGF modules within the family of low-density lipoprotein receptors (LDLRs). Acts as a modulator of the Wnt pathway through chaperoning the coreceptors of the canonical Wnt pathway, LRP5 and LRP6, to the plasma membrane. Essential for specification of embryonic polarity and mesoderm induction. Plays an essential role in neuromuscular junction (NMJ) formation by promoting cell-surface expression of LRP4. May regulate phagocytosis of apoptotic retinal pigment epithelium (RPE) cells. Monomer. Interacts with LRP5; the interaction prevents LRP5 from forming aggregates and chaperones LRP6 to the plasma membrane. Interacts with LRP6; the interaction prevents LRP6 from forming aggregates and chaperones LRP6 to the plasma membrane. Interacts with LRP4; the interaction promotes glycosylation of LRP4 and its cell-surface expression. Released from apoptotic cells and shed photoreceptor outer segments (By similarity). The chaperone domain provides a folding template for proper folding of the beta-propeller (BP) domains of LRP5/6. The escort domain ensures LRP5/6 safe-trafficking from the ER to the Golgi by preventing premature ligand-binding. Belongs to the MESD family.