Proteomic Study of the Mucin Granulae in an Intestinal Goblet Cell Model

Goblet cells specialize in producing and secreting mucus
with its
main component, mucins. An inducible goblet-like cell line was used
for the purification of the mucus vesicles stored in these cells by
density gradient ultracentrifugation, and their proteome was analyzed
by nanoLC-MS and MS/MS. Although the density of these vesicles coincides
with others, it was possible to reveal a number of proteins that after
immunolocalization on colon tissue and functional analyses were likely
to be linked to the MUC2 vesicles. Most of the proteins were associated
with the vesicle membrane or their outer surface. The ATP6AP2, previously
suggested to be associated with vesicular proton pumps, was colocalized
with MUC2 without other V-ATPase proteins and, thus, probably has
roles in mucin vesicle function yet to be discovered. FAM62B, known
to be a calcium-sensitive protein involved in vesicle fusion, also
colocalized with the MUC2 vesicles and is probably involved in unknown
ways in the later events of the MUC2 vesicles and their secretion.