Fig. 1.

Outline for exosome secretion. a Normal stimulation of the insulin receptor leads to tyrosine phosphorylation of the insulin receptor susbtrate-1 (IRS1), initiating phosphorylated protein kinase b (Akt) inhibition of glycogen synthase kinase (GSK)-3β and activation of pro-survival signals. b Lack of stimulation or overstimulation at the insulin receptor leads to serine phosphorylation of the IRS1, which leads to dephosphorylated Akt activation of GSK-3β. c GSK-3β inhibits the autophagosome induction to the lysosome and promotes the introduction of the autophagosome to the multivesicular body (MVB). d Endocytosis allows for introduction of internalized proteins into the MVB. e MVB associates with the plasma membrane, allowing for exosome release from the cell