4). SED1/MFG-E8 is secreted in association with exosomes.

A) SED1/MFG-E8 may be secreted as a soluble protein through classical mechanisms, however SED1/MFG-E8's association with microvesicles suggests it is also secreted through non-classical pathways including B) apocrine shedding, as occurs in the epididymis, and C) fusion of multivesicular bodies (MVB) with the apical plasma membrane. Both apocrine shedding and MVB fusion result in the release of microvesicles, called exosomes, into the extracellular milieu.